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Health

Think All Viruses Get Milder With Time? Not This Rabbit-Killer.

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As the Covid death rate worldwide has fallen to its lowest level since the early weeks of the pandemic in 2020, it may be tempting to conclude that the coronavirus is becoming irreversibly milder. That notion fits with a widespread belief that all viruses start off nasty and inevitably evolve to become gentler over time.

“There’s been this dominant narrative that natural forces are going to solve this pandemic for us,” said Aris Katzourakis, an evolutionary biologist at the University of Oxford.

But there is no such natural law. A virus’s evolution often takes unexpected twists and turns. For many virologists, the best example of this unpredictability is a pathogen that has been ravaging rabbits in Australia for the past 72 years: the myxoma virus.

Myxoma has killed hundreds of millions of rabbits, making it the most deadly vertebrate virus known to science, said Andrew Read, an evolutionary biologist at Pennsylvania State University. “It’s absolutely the biggest carnage of any vertebrate disease,” he said.

After its introduction in 1950, myxoma virus became less lethal to the rabbits, but Dr. Read and his colleagues discovered that it reversed course in the 1990s. And the researchers’ latest study, released this month, found that the virus appeared to be evolving to spread even more quickly from rabbit to rabbit.

“It’s still getting new tricks,” he said.

Scientists intentionally introduced the myxoma virus to Australia in the hopes of wiping out the country’s invasive rabbit population. In 1859, a farmer named Thomas Austin imported two dozen rabbits from England so he could hunt them on his farm in Victoria. Without natural predators or pathogens to hold them back, they multiplied by the millions, eating enough vegetation to threaten native wildlife and sheep ranches across the continent.

In the early 1900s, researchers in Brazil offered Australia a solution. They had discovered the myxoma virus in a species of cottontail rabbit native to South America. The virus, spread by mosquitoes and fleas, caused little harm to the animals. But when the scientists infected European rabbits in their laboratory, the myxoma virus proved astonishingly lethal.

The rabbits developed skin nodules packed with viruses. Then the infection spread to other organs, usually killing the animals in a matter of days. This gruesome disease came to be known as myxomatosis.

The Brazilian scientists shipped samples of the myxoma virus to Australia, where scientists spent years testing it in labs to make sure it posed a threat only to rabbits and not other species. A few scientists even injected myxoma viruses into themselves.

After the virus proved safe, researchers sprayed it into a few warrens to see what would happen. The rabbits swiftly died, but not before mosquitoes bit them and spread the virus to others. Soon, rabbits hundreds of miles away were dying as well.

Shortly after myxoma’s introduction, the Australian virologist Dr. Frank Fenner started a careful, long-term study of its carnage. In the first six months alone, he estimated, the virus killed 100 million rabbits. Dr. Fenner determined in laboratory experiments that the myxoma virus killed 99.8 percent of the rabbits it infected, typically in less than two weeks.

Yet the myxoma virus did not eradicate the Australian rabbits. Through the 1950s, Dr. Fenner discovered why: The myxoma virus grew less deadly. In his experiments, the most common strains of the virus killed as few as 60 percent of the rabbits. And the rabbits the strains did kill took longer to succumb.

This evolution fit with popular ideas at the time. Many biologists believed that viruses and other parasites inevitably evolved to become milder — what came to be known as the law of declining virulence.

“Longstanding parasites, by the process of evolution, have much less of a harmful effect on the host than have recently acquired ones,” the zoologist Gordon Ball wrote in 1943.

According to the theory, newly acquired parasites were deadly because they had not yet adapted to their hosts. Keeping a host alive longer, the thinking went, gave parasites more time to multiply and spread to new hosts.

The law of declining virulence seemed to explain why myxoma viruses became less lethal in Australia — and why they were harmless back in Brazil. The viruses had been evolving in South American cottontail rabbits much longer, to the point that they caused no disease at all.

But evolutionary biologists have come to question the logic of the law in recent decades. Growing milder may be the best strategy for some pathogens, but it is not the only one. “There are forces that can push virulence in the other direction,” Dr. Katzourakis said.

Dr. Read decided to revisit the myxoma virus saga when he started his laboratory at Penn State in 2008. “I knew it as a textbook case,” he said. “I started thinking, ‘Well, what’s happening next?’”

No one had systematically studied the myxoma virus after Dr. Fenner stopped in the 1960s. (He had good reason to abandon it, as he had moved on to help eradicate smallpox.)

Dr. Read arranged for Dr. Fenner’s samples to be shipped to Pennsylvania, and he and his colleagues also tracked down more recent myxoma samples. The researchers sequenced the DNA of the viruses — something that Dr. Fenner could not do — and carried out infection studies on lab rabbits.

When they tested the viral lineages that had been dominant in the 1950s, they found that they were less lethal than the initial virus, confirming Dr. Fenner’s findings. And the fatality rate stayed relatively low through the 1990s.

But then, things changed.

Newer viral lineages killed more of the lab rabbits. And they often did so in a new way: by shutting down the animals’ immune systems. The rabbits’ gut bacteria, normally harmless, multiplied and caused lethal infections.

“It was truly scary when we first saw that,” Dr. Read said.

Strangely, wild rabbits in Australia have not suffered the grisly fate of Dr. Read’s laboratory animals. He and his colleagues suspect that the new adaptation in the viruses was a response to stronger defenses in the rabbits. Studies have revealed that Australian rabbits have gained new mutations in genes involved in the first line of disease defense, known as innate immunity.

As the rabbits developed stronger innate immunity, Dr. Read and his colleagues suspect, natural selection, in turn, favored viruses that could overcome this defense. This evolutionary arms race erased the advantage the wild rabbits had briefly enjoyed. But these viruses proved even worse against rabbits that had not evolved this resistance, such as those in Dr. Read’s laboratory.

And the arms race is still unfolding. Roughly a decade ago, a new lineage of myxoma viruses emerged in southeastern Australia. This branch, dubbed Lineage C, is evolving much faster than the other lineages.

Infection experiments suggest that new mutations are allowing Lineage C to do a better job of getting from host to host, according to the latest study by Dr. Read and his colleagues, which has not yet been published in a scientific journal. Many infected rabbits display a strange form of myxomatosis, developing massive swellings on their eyes and ears. It is precisely these places where mosquitoes like to drink blood — and where the viruses may have a better chance of reaching a new host.

Virologists see some important lessons that the myxoma virus can offer as the world grapples with the Covid pandemic. Both diseases are influenced not only by the genetic makeup of the virus, but the defenses of its host.

As the pandemic continues its third year, people are more protected than ever thanks to the immunity that has developed from vaccinations and infections.

But the coronavirus, like myxoma, has not been on an inevitable path to mildness.

The Delta variant, which surged in the United States last fall, was more deadly than the original version of the virus. Delta was replaced by Omicron, which caused less severe disease for the average person. But virologists at the University of Tokyo have carried out experiments suggesting that the Omicron variant is evolving into more dangerous forms.

“We don’t know what the next step in evolution will be,” Dr. Katzourakis warned. “That chapter in the trajectory of virulence evolution has yet to be written.”

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Health

Depression, anxiety may linger for bedridden COVID patients but milder infections reduce risk, study finds

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People who were bedridden for a week or more with COVID-19 remain at increased risk for anxiety and depression more than a year later, according to a new study.

But those who had milder infections are actually at lower risk for mental health problems than the general public.

“The good news is that the patient group as a whole is not at higher risk of developing long-term (mental health) symptoms,” said Unnur Anna Valdimarsdóttir, a psychiatric epidemiologist at the University of Iceland, who helped lead the research.

A mild infection could even boost mental health. “There might be a relief associated with having gone through the infection,” she said.

Nearly 80% of those who had COVID-19 are not at higher risk for persistent mental health symptoms, she said.

‘AMPLE ROOM FOR UNCERTAINTY’: As COVID-19 cases rise again in Europe, could U.S. see the same?

The study is the first to look at large numbers of people who were infected but not sick enough to go the hospital and to follow them for such a long time, said Dr. Stephanie Collier, a geriatric psychiatrist at McLean Hospital in Belmont, Massachusetts.

Doctors have assumed that sicker patients were at higher risk for depression and anxiety, but the risk wasn’t clear for those who didn’t need hospital care, she said.

It’s also good news for people who weren’t severely ill. “This study helps share that not every mild infection is going to end up with lingering symptoms,” she said.

An Indonesian health worker prepares Bio Pharma COVID-19 vaccine on Aug. 6, 2021 in Surabaya, Indonesia.

The cause of longer-term depression or anxiety after infection remains unclear. But a mental health challenge triggered by an infection might eventually be treated differently than one that arose without an obvious start date, said Collier, who now asks all of her patients whether they’ve been infected with COVID-19.

Most of her patients who complain of new depression or anxiety also suffer other symptoms of so-called long COVID, including severe fatigue or the inability to concentrate long enough to read a book or pursue work or a hobby, she said.

“Time will tell,” she said, whether depression that starts after a COVID-19 infection is any different from other forms of depression.

The new study, began before the pandemic, when a group of scientists from six countries, including the U.K., Denmark, Sweden and Iceland, came together to study mental health. In the early days of COVID-19 they decided to shift gears and track nearly 300,000 volunteers as they endured the pandemic.

Roughly 10,000 fell ill between late March 2020 and mid-August 2021, with about 2,200 sick enough to stay in bed for a week or more and 300 ending up in the hospital.

Valdimarsdóttir and her colleagues showed that those who spent seven or more days lying in bed were at 50% to 60% increased risk of suffering from depression or anxiety 16 months later.

“The symptoms in this group seemed persistent,” Valdimarsdóttir said, not improving with time, “which is worrying.”

People who were quite ill originally and are still suffering should not feel like they are the only ones, and their doctors should target them for follow-up and extra assistance, Valdimarsdóttir said.

During infection many people suffered acute stress, concerned about how severe their illness would become. They often developed nightmares and anxiety, but these decreased over time in all groups, the study showed.

Meanwhile, people who came through infections relatively unscathed felt like they no longer had to worry about the virus or potential long-term consequences.

The study could not explain why people have lingering symptoms, but the fact that they were quite sick initially suggests that excessive inflammation during the infection could lead to these longer-term problems. “We need to explore these mechanisms in further detail,” Valdimarsdóttir said.

Contact Weintraub at kweintraub@usatoday.com

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: COVID: Anxiety, depression lingers for bedridden patients, study finds

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Health

Omicron is milder, but scientists say it’s still too soon to relax

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A sign reminding riders to wear a face mask to prevent the spread of Covid-19 appears on a bus on First Street outside the U.S. Capitol on Monday, January 10, 2022.

Tom Williams | CQ-Roll Call, Inc. | Getty Images

Infectious disease experts have warned that it’s too soon for the public to stop taking steps to avoid Covid-19 infection, despite health officials claiming it’s inevitable most people will catch the seemingly milder omicron variant.

Many countries now have few or no Covid-related restrictions remaining, as surging case numbers are weighed against vaccination rates. The leaders of some European countries have called for the coronavirus crisis to begin its shift from pandemic to endemic, and be treated like the seasonal flu.

In the U.K., where new cases are beginning to ease from record-high levels after a December surge, the government is reportedly drawing up plans to completely scrap its emergency Covid laws, including self-isolation requirements, according to The Telegraph.

Official data published on Monday showed that around 98% of the U.K. population now has antibody protection against the virus, either through vaccination or infection. Just over 80% of the country’s population has received two doses of a Covid vaccine.

There is a consensus among many that the highly transmissible omicron variant is so infectious, everybody will eventually contract Covid. White House chief medical advisor Dr. Anthony Fauci predicted the strain will “find just about everybody,” CNN reported last week.

However, many scientists are still urging the public to do what they can to avoid infection.

Professor Liam Smeeth, a physician and director of the London School of Hygiene and Tropical Medicine, told CNBC that while omicron appears inherently milder, scientific knowledge is still “not as complete as we’d like” on how the heavily mutated variant will impact vulnerable individuals.

“If the vulnerable do become quite unwell with omicron — and some of them will — if that all happens at once, if we just let it rip through society, then any health system in the world would get overwhelmed,” he said in a phone call.

“And that is a very, very grim thought — so grim as to be quite terrifying. It’s clear that most people don’t get very unwell with omicron, but we don’t have clear evidence that that’s true of everyone.”

Smeeth added that omicron’s increased transmissibility meant it still posed big risks, despite appearing to cause milder symptoms.

“Because it’s so infectious, it literally could be millions of very unwell people all at the same time, which no health system could cope with,” he explained.

“You’ve also got the fact that people are going to be off sick — it doesn’t cause serious illness, but it does cause enough that people need to stay at home [to recover]. And if that happens across the whole of society all at once, even in the space of a few weeks, that means the police are going to struggle, supermarkets aren’t going to open, the health system’s not going to function — there would be pretty big social disruption going on.”

“So even if it’s reasonably mild, there are reasons to want it to happen more gradually,” he said.

Public health officials have also warned about the risk of “long Covid.” The WHO has previously estimated that between 10% to 20% of Covid patients experience lingering symptoms for months following infection. These prolonged symptoms can include persistent fatigue, breathlessness, brain fog and depression.

In the U.K., where Covid isolation times were cut down to five days on Monday, Smeeth said he believed the government was implementing a “pretty sensible, gradual stepping down.”

Meanwhile, Philip Anyanwu, a lecturer in public health at Cardiff University’s School of Medicine, noted a perception that the omicron variant is making Covid less of a threat was becoming more common among the general population.

“Regardless of it [causing milder symptoms], I think we still need to keep those measures that helped us get through, especially wearing face masks, social distancing and frequently washing our hands,” he said via telephone.

He argued it was too soon for the public to stop trying to reduce Covid-related risks, particularly in the winter — the “most crucial period in terms of infectious disease burden.”

Deepti Gurdasani, senior lecturer in epidemiology at Queen Mary University of London, said via Twitter on Sunday that living with the virus “doesn’t mean doing nothing and letting ‘mostly the old and vulnerable die.'”

“People wearing high-grade masks and good ventilation aren’t restrictive but save a lot of lives,” she said.

“Are we seriously saying we won’t even lift a finger to save lives of people who are ‘old and vulnerable?'”

Risk of Covid ‘Armageddon’

Smeeth warned that although there was reason to be cautiously optimistic, it was still too early to completely rule out further surprises.

“Everything in history would tell you that this variant is so mutated, that there are only a few more mutations it can do, and the history of coronaviruses is that they tend to mutate into a milder form on their way out to becoming either endemic in society or just disappearing altogether,” he said. “That does seem to be where [omicron] is going. It’s very infectious, so it’s going be quite hard to replace.”

However, Smeeth added that Covid “behaves quite differently to other coronaviruses,” warning that it would be foolish to rule out another new, more severe variant.

“It could well come up with another variant that causes more severe illness and is more infectious — it really could be Armageddon, it really could be the stuff of science fiction, just like we saw last year.”

Anyanwu agreed that it was still too early to completely relax.

“We know that omicron is more transmissive but not as serious as other variants — but there is no guarantee of what the next variant is going to be,” he said.

“One of the reasons omicron spread so widely is because when it came into the U.K. population, a lot of public health measures had been reduced. We were playing more of a reactive approach to controlling it rather than being proactive.”

He added that the world was still in the midst of the pandemic and it was too soon for a return to complete normality.

“Getting rid of all measures puts us at risk if there’s any new variant that comes in,” he warned. “It might be less transmissive or more transmissive, it might be more serious in terms of outcomes like death and hospitalization.”

“It’s reasonable for individuals to stick to some measures, even when we have a lot of the government’s rules being relaxed,” Anyanwu cautioned.

“Regardless of whether government restrictions remain or are taken away, individuals can still make decisions on how they go about their daily activities.”

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Health

Omicron Is Milder Than Delta But Still Wreaking Havoc

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The paradox of Omicron, now responsible for an estimated 98.3% of all US coronavirus cases, is that while it seems more likely to result in significantly milder outcomes than Delta and previous variants, the health system is as stressed as it’s ever been.

Public health officials are warning that Omicron is threatening to overwhelm the medical infrastructure with sheer numbers, and hospitals are filled with seriously ill patients.

“It’s going to get worse before it gets better,” said Dean Blumberg, a pediatrician and infectious disease expert at the University of California, Davis.

Here’s what we know about why this is happening:

Omicron is more contagious

The variant appears to be roughly two to five times more transmissible than Delta, which previously dominated US cases.

“This is the second-most contagious disease in the world now, second to measles,” said Sara Murray, the director of the health informatics data science and innovation team and an associate professor of clinical and hospital medicine at the University of California San Francisco.

“While we are seeing early evidence that Omicron is less severe than Delta and that those infected are less likely to require hospitalization, it’s important to note that Omicron continues to be much more transmissible,” CDC Director Rochelle Walensky said on Wednesday.

This means that even though a smaller percentage of patients infected with Omicron require hospitalization, the total number of COVID cases is so high that hospitals are seeing more of those patients than at any point in the pandemic.

COVID-19 cases have reached record levels in the US, averaging around 1.4 million new reported cases a day, itself an undercount. Daily, an average of 19,800 people nationwide are now admitted to hospitals with COVID, according to the CDC, a 33% increase over the past week. Almost a third of intensive care unit beds nationwide are now filled with COVID patients, meaning roughly 1 out of every 2.5 people in an ICU ward in the country has the virus

More patients are being admitted “with” COVID

COVID is so widespread right now that a significant percentage of hospitalized patients are admitted for something else but then test positive upon screening at admittance.

“We test a lot of asymptomatic patients in preparation for procedures or surgeries, planned hospitalizations — and even in those folks who are totally asymptomatic, we’re seeing a case positivity right now of about 12%,” Murray said.

“It’s a very different landscape that we’re seeing with overcrowding in the hospital than we’ve seen with the prior waves of COVID,” said Richelle Charles, an infectious disease expert at Massachusetts General Hospital and Harvard Medical School. “Almost half of these cases are in the hospital for non-COVID-related illnesses.”

At UCSF, Murray said overall about two-thirds of their COVID patients were hospitalized for the disease, while one-third were hospitalized with it. In pediatric COVID patients, about half of them were admitted for something other than the disease.

Yet even if these patients’ COVID symptoms are mild or nonexistent, their positive status places an extra burden on the hospital because they require isolation and extra safety protocols for hospital staff.

Staffing shortages from exposure and burnout

Hidden in the increasing case numbers are doctors, nurses, and other healthcare personnel infected by the more contagious variant, which causes more breakthrough infections among the vaccinated than past ones, said Akin Demehin, the policy director at the American Hospital Association. Even with mild infections, those healthcare workers are still out of action for a week after their tests turn negative, per CDC policy, just as the surge fills up hospitals and drives up demand for staff.

The Omicron surge will only put more stress on doctors and nurses, who still have to care for all those extra patients. One survey last August reported that nearly 60% of doctors feel burned out, Demehin said, and that was two surges ago. “We hear this from hospital leaders all the time — their number one, two, and three priority right now is workforce,” he said. “They know just how much has been asked of healthcare providers over the past almost two years.”

More young children

“This time around, we’re seeing more children less than 5 years of age,” Blumberg said.

He has observed that many of them have milder cases of bronchitis or croup, whereas the teens with COVID seen in earlier surges had more severe pneumonia. Most of these young children recover well, but he cautioned that with any infection and any hospital admission, “some children aren’t going to do well.”

Hospitalizations among young children are currently higher than they’ve ever been during the pandemic, according to the CDC.

Vaccines still work, but boosters are important

One thing the Omicron surge hasn’t altered is the well-established reality that vaccines significantly improve people’s odds of not dying from COVID-19. Deaths are still on the increase, averaging 1,600 a day in the US, an increase of 40% from the past week, according to the CDC. (Walensky said at the White House briefing that she thinks most of those are Delta variant cases.)

With Omicron rampant, “virtually everybody is going to wind up getting exposed and likely get infected,” National Institute of Allergy and Infectious Diseases chief Anthony Fauci said on Wednesday. “But if you’re vaccinated, and if you’re boosted, the chances of you getting sick are very, very low.”

“At my hospital, we have a graphic that’s sent out every day that has little people icons, those in the ICU, those on a ventilator, and those admitted for COVID. And the vast majority, overwhelmingly, are unvaccinated people in all three categories,” said Jeanne Marrazzo, the director of the division of infectious diseases at the University of Alabama at Birmingham School of Medicine, who spoke Tuesday at an Infectious Diseases Society of America briefing on Omicron for reporters.

“What we’ve learned with Omicron is that the booster really makes a big difference in terms of reducing your risk,” Murray said. Her hospital is seeing both vaccinated and unvaccinated patients hospitalized for COVID. But even patients who only had an initial series of vaccines — no booster — appear to be protected from the most severe outcomes.

“What we aren’t seeing is patients ending up on ventilators if they’re fully vaccinated,” she said. “I don’t have a single fully vaccinated patient in the hospital on a ventilator right now.”

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World

WHO sees more evidence that Omicron causes milder symptoms

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  • WHO sees some ‘decoupling’ of COVID-19 cases and deaths
  • Raising global vaccine rates will reduce Omicron’s impact
  • Calls for global coordination on vaccine development

GENEVA, Jan 4 (Reuters) – More evidence is emerging that the Omicron coronavirus variant is affecting the upper respiratory tract, causing milder symptoms than previous variants and resulting in a “decoupling” in some places between soaring case numbers and low death rates, a World Health Organization official said on Tuesday.

“We are seeing more and more studies pointing out that Omicron is infecting the upper part of the body. Unlike other ones, the lungs who would be causing severe pneumonia,” WHO Incident Manager Abdi Mahamud told Geneva-based journalists.

“It can be a good news, but we really require more studies to prove that.”

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Since the heavily mutated variant was first detected in November, WHO data shows it has spread quickly and emerged in at least 128 countries, presenting dilemmas for many nations and people seeking to reboot their economies and lives after nearly two years of COVID-related disruptions.

However, while case numbers have surged to all-time records, the hospitalisation and death rates are often lower than at other phases in the pandemic.

“What we are seeing now is….the decoupling between the cases and the deaths,” he said.

His remarks on the reduced risks of severe disease chime with other data, including a study from South Africa, which was one of the first countries where Omicron was detected.

However, Mahamud also sounded a note of caution, calling South Africa an “outlier” since it has a young population, among other factors.

And he warned that Omicron’s high transmissibility meant it would become dominant within weeks in many places, posing a threat to medical systems in countries where a high proportion of the population remains unvaccinated.

VACCINATION, NOT VACCINES, ARE THE CHALLENGE

While Omicron seemed to be slipping past antibodies, evidence was emerging that COVID-19 vaccines still provided some protection, by eliciting a second pillar of the immune response from T-cells, Mahamud said.

“Our prediction is protection against severe hospitalization and death (from Omicron) will be maintained,” he said, saying this also applied to vaccines developed by Sinopharm and Sinovac that are used in China, where Omicron cases remain very low.

“The challenge has not been the vaccine but the vaccination and reaching those vulnerable populations.”

Asked about whether an Omicron-specific vaccine was needed, Mahamud said it was too early to say but voiced doubts and stressed that the decision required global coordination and should not be left to manufacturers to decide alone.

“You may go ahead with Omicron and put all your eggs in that basket and a new variant that is more transmissible or more immune-evasive may appear,” he said, adding that a WHO technical group had held recent meetings on vaccine composition.

The best way to reduce the impact of the variant would be to meet the WHO’s goal of vaccinating 70% of the population in each country by July, rather than offer third and fourth doses in some countries, he said.

As case numbers due to Omicron have soared, some countries, including the United States, have cut down isolation or quarantine periods in a bid to allow asymptomatic people to return to work or school.

Mahamud said that leaders should decide based on the strength of the local epidemic, saying Western countries with very high case numbers might consider trimming isolation periods to keep basic services functioning.

However, places that have largely shut it out would do better to maintain the full 14-day quarantine period.

“If your numbers are very small, you better be invested in keeping that number very, very low.”

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Reporting by Emma Farge and Mrinalika Roy in Bangalore; Editing by Andrew Cawthorne and Alex Richardson

Our Standards: The Thomson Reuters Trust Principles.

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Health

Omicron variant less severe due to milder effect on lungs – study

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The Omicron variant is less severe in comparison to other SARS-CoV-2 variants as the lungs are mostly spared in such COVID-19 cases, according to new animal research.

Omicron had less severe effects on small animals such as hamsters and mice, The New York Times reported on Saturday. Infection by the variant that were detected caused less severe damage to the nose, throat and windpipe.

Animal research can reportedly help clear up questions regarding the new research, the Times report stated. It also cited data suggesting that the Omicron variant is milder than Delta and other SARS-CoV-2 ones. This was confirmed when scientists concluded that hamsters became severely ill from all other variants of the coronavirus.

Other studies showed that the presence of Omicron in the lungs was a tenth or less than the viral load of other variants. One study, published in the peer-reviewed journal Nature by Hong Kong University researchers, confirmed that Omicron replicated more slowly than Delta and other coronavirus variants.
Last Tuesday, another study published in Live Science reported that Omicron is unlikely to “[enter] lung cells,” adding that some of the initial data from South Africa, the variant’s country of origin, indicated that the strain causes less damage.

People pose with syringe with needle in front of displayed words ”OMICRON SARS-COV-2” in this illustration taken, December 11, 2021 (credit: REUTERS/DADO RUVIC/ILLUSTRATION/FILE PHOTO)

A study published in bioRxiv stated that the new variant dodges most of the antibodies made by those who are fully vaccinated.
Regarding the pandemic, Israel registered almost 5,000 new COVID-19 cases last Thursday and approved a fourth vaccine shot to be given to those who are at risk of contracting the virus or suffering from severe symptoms. This was announced by Health Ministry Dir.-Gen. Prof. Nachman Ash.
In the US, health experts warned citizens that “a rising tide of COVID-19 cases led by the Omicron variant threatens major disruptions to their lives.”

Rossella Tercatin and Reuters contributed to this report.



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Health

Omicron might be milder because it has a less effective way of attacking lung cells, studies say

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An annotated schematic of entry routes used by the coronavirus shows the difference between Omicron and Delta, according to a recent study.Georgina Brown/Joe Grove/Insider

  • Two recent lab studies suggested a reason Omicron could be more mild than other variants.

  • They said its way of attacking cells works badly in the lungs, where the virus does the most damage.

  • But Omicron’s method is more effective elsewhere, which could account for its infectiousness.

The Omicron coronavirus variant might be less severe in humans because it attacks human lung cells in a different way, according to two laboratory studies published recently.

A group of 31 scientists from different universities collaborated on the project for the first study. The second study was authored by 34 scientists from Scottish and English institutes. Both studies were published in preprint form, which means they have yet to be reviewed by other scientists.

The researchers said that Omicron’s numerous mutations appear to have completely changed how it replicates itself in the body.

Omicron “is actually doing its own thing in many ways,” Ravindra Gupta, a leading variant researcher from Cambridge University and an author on the first study, told Insider.

“The biology of the virus is not the same as it was before. It’s almost a new thing.”

This provides new evidence supporting the idea that Omicron is less dangerous, Gupta said. Numerous other studies, and some real-world data, have suggested the virus is causing less severe disease and fewer deaths.

Experts have been hesitant to accept the findings too quickly, hoping for more conclusive data. The paper by Gupta and his colleagues could help explain the difference in severity.

Two ways to take over the body

There are two ways the virus can infect a cell.

One way relies on the shell of the virus fusing with the membrane of the human cell. This route, called “cell-surface fusion,” is the route Delta prefers, according to Gupta’s previous work.

Cell-surface fusion can be used only if a cell carries high levels of a molecule called TMPRSS2, which in the case of the coronavirus snips the virus’s spike protein in half.

An annotated schematic of entry routes used by the coronavirus shows the difference between Omicron and Delta, according to a recent study.Georgina Brown/Joe Grove

TMPRSS2 is found in large quantities in the lungs, meaning that variants like Delta can thrive there, causing serious damage to the people it infects.

“That is thought to be one of the dominant roots for infection in deep lung tissue that’s associated with more severe disease,” said Gupta

Delta’s mutations mean it is much better at having its spike protein snipped than other variants, Gupta said.

By contrast, Omicron’s spike protein is very difficult to snip in half, according to lab-test results cited in the study on which Gupta is an author. This would make it worse at infecting the lungs in the way Delta does.

On the other hand, Omicron’s spike protein is much better at binding to human cells in general, which gives it an advantage in cells without TMPRSS2, the study said.

Airway cells have low levels of TMPRSS2, so Omicron is much more suited to infect these cells using a route called endosomal fusion, according to the study. This would make it more capable of causing infections with mild symptoms.

An annotated schematic shows the location of a bronchus and a lung.Insider; QAI Publishing/Universal Images Group via Getty Images

These findings come after other lab studies observed Omicron replicating much faster in airway and bronchial cells than in the lungs.

Real-world data supports this finding, as Omicron appears to have led to a smaller percentage of hospitalizations than Delta in South Africa, the UK, and the US.

The results are preliminary, but they support the idea that the variant is less dangerous, Gupta said.

“So this is what we think ties it all together,” he said.

Good news and bad news

“We probably need to express some caution. It is nice to see that this variant is potentially less severe. But we don’t know by how much yet,” Gupta said.

It’s also not clear whether Omicron could cause other long-term consequences, collectively known as long COVID, as was the case in other variants.

Gupta also warned that it might be possible for future variants to appear that are again more deadly. “The next variant could have combined characteristics, so I don’t think we can be complacent,” he said.

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Omicron Reinfections Can Trigger Milder Symptoms, New CDC Research Shows

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The Centers for Disease Control and Prevention added to research suggesting the Omicron variant can lead to reinfections that are often accompanied by mild Covid-19 symptoms, as new cases soared across the U.S.

States reported 512,553 cases on Monday—the most for a single day since the start of the pandemic—as states caught up after pausing for the Christmas holiday, according to a Wall Street Journal analysis of data from Johns Hopkins University. The tally lifted the seven-day average of reported cases to 237,061, 15,000 less than the pandemic high recorded about a year ago.

The report for Monday didn’t include North Carolina, South Carolina and Rhode Island, which remained on pause. That gap and more blackouts in reporting during the New Year weekend are expected to muddy the tracking of the full extent of the pandemic’s trajectory until January, when reporting catches up.

Covid-19 testing was also less prevalent earlier in the pandemic, complicating case-rate comparisons from one surge to another. As with earlier variants, tracking Omicron’s spread in the U.S. has been a challenge for public-health officials. The CDC on Tuesday estimated that Omicron was responsible for 59% of new infections for the week through Dec. 25 and 23% for the week through Dec. 18. Last week, the CDC had estimated Omicron drove some 73% of infections in the week through Dec. 18. The CDC said Tuesday that the latest figures fell within the bounds of its statistical model and that the trend of Omicron’s increasing prevalence among U.S. cases is clear.

The CDC on Tuesday also released a review of a cluster of recent Covid-19 cases in a family of six in Nebraska. The cases indicate that Omicron is able to infect people who have had past infections, and that it causes milder symptoms in some people with some immunity, either from a vaccine or past infection. Also, Omicron seems to bring about symptoms sooner—in about three days following exposure, rather than five or later, the agency said.

The first suspected case in the cluster was a 48-year-old man who returned from Nigeria on Nov. 23 and showed Covid-19-like symptoms a day later. By Dec. 1, all six family members had positive SARS-CoV-2 PCR tests, and sequencing confirmed the Omicron variant in each case. Five members of the family, including the only person who is fully vaccinated, had confirmed infections about a year ago. They each experienced symptoms similar to or more mild than those during their past infection. The one unvaccinated family member who didn’t have a confirmed infection had cough, joint pain, congestion, fever and chills. No one in the family was hospitalized, the CDC said.

Scientists are using automation, real-time analysis and pooling data from around the world to rapidly identify and understand new coronavirus variants before the next one spreads widely. Photo Illustration: Sharon Shi

The CDC on Monday reduced the recommended isolation period for people infected with Covid-19 to five days from 10. The new guidance reflects growing evidence that people with the virus are most infectious one to two days before the onset of symptoms and two to three days afterward, the agency said, as well as concern over the disruption staff outages are causing in the travel and healthcare sectors.

The CDC now says that infected people who are asymptomatic can leave isolation after five days and should wear masks when around other people for another five, while those vaccinated and exposed to someone with Covid-19 should wear a mask for 10 days and try to get tested five days after exposure.

The CDC should have included a requirement that people test negative with rapid tests before ending isolation, said

Angela Rasmussen,

a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan. “Test-to-release using rapid testing is sensible and would really reduce the likelihood of someone who is still contagious potentially transmitting the virus to others,” she said.

If the CDC’s new guidelines are adopted, they could enable people to return to work more quickly and avoid snarling key industries. Thousands of flights were canceled over the Christmas weekend, while officials in the U.S. and elsewhere have expressed concern over how quarantines are affecting hospital staffing levels.

The Food and Drug Administration said Tuesday that some antigen tests, the basis of many at-home rapid tests, are able to detect the Omicron variant but “may have reduced sensitivity” to it. The data come from a collaboration between the FDA and the National Institutes of Health’s RADx program to assess how successfully antigen tests detect Omicron in samples from infected patients. Antigen tests are known to sometimes yield false negative results.

New York City will send children back to public schools on Monday while ramping up testing capacity and making it easier for children who are exposed to stay in school, the mayor, the governor and incoming Mayor

Eric Adams

said Tuesday.

Research in South Africa and the U.K. suggests that Omicron causes a milder form of Covid-19 among vaccinated people than previous strains; shoppers in London on Monday.



Photo:

David Cliff/Associated Press

The city and state are going to provide some three million rapid test kits that will be distributed to students and staff who are in a classroom with a positive case. Students who test negative and are asymptomatic will be able to remain in school. Officials said they plan to double the amount of regular testing of students in schools to track potential outbreaks and expand eligibility to include vaccinated students as well as staff.

President

Biden

officially revoked a ban on non-U.S. citizens traveling from countries in southern Africa, effective Dec. 31. Mr. Biden announced the ban last month after the Omicron variant was first identified in South Africa. An administration official said last week that Mr. Biden would lift the restrictions.

Research carried out in South Africa and the U.K. suggests that Omicron, while more transmissible, causes a milder form of the disease among vaccinated people than previous strains, such as Delta. A new study from the South African lab that has been at the forefront of research into Omicron suggests that infection with the new variant provides protection against Delta.

Scientists at the Africa Health Research Institute looked at 15 vaccinated and unvaccinated people who had been infected with Omicron. When they tested their blood samples against the Delta variant, they found a more than fourfold increase in antibodies against the virus over a two-week period.

A technician in a Covid-19 research lab at Africa Health Research Institute in Durban, South Africa, earlier this month.



Photo:

Waldo Swiegers/Bloomberg News

Those who had been vaccinated produced a stronger response against Delta, according to the study, which hasn’t been peer reviewed.

“If Omicron does prove to be less pathogenic, then this may show that the course of the pandemic has shifted—Omicron will take over, at least for now, and we may have less disruption of our lives,” said

Alex Sigal,

who led the study.

The researchers cautioned that prior infection from other variants and vaccination might have contributed to the increased protection from Delta rather than the Omicron infection alone, spurring an increase in antibodies against Delta.

—Laura Kusisto, Anthony DeBarros and Tarini Parti contributed to this article.

Write to Nidhi Subbaraman at Nidhi.Subbaraman@wsj.com and James Hookway at james.hookway@wsj.com

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Omicron may cause milder disease. A lab study hints at why.

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The omicron variant of SARS-CoV-2 may be less efficient at infiltrating the lungs and spreading from cell to cell, compared with other versions of the coronavirus, early studies of human cells in a lab dish suggest. 

This may help explain why some early data from countries such as South Africa and England suggest the strain causes less severe disease. But although omicron may not invade lung cells efficiently, the new study, posted Tuesday (Dec. 21) to the preprint database bioRxiv, confirmed that the variant dodges most of the antibodies made by fully vaccinated individuals. 

And similar to other research, the team showed a “booster” dose of the Pfizer vaccine significantly increased the neutralization power of vaccinated people’s antibodies, “though we’d still expect a waning in immunity to occur over time,” senior author Ravindra Gupta, a professor of clinical microbiology at the Cambridge Institute for Therapeutic Immunology and Infectious Diseases, said in a statement.

Related: Coronavirus variants: Facts about omicron, delta and other COVID-19 mutants

The research has not yet been peer-reviewed or published in a scientific journal, but the findings hint “that omicron’s mutations present the virus with a double-edged sword: it’s got better at evading the immune system, but it might have lost some of its ability to cause severe disease,” Gupta said. That said, scientists still need to confirm that these results from experiments in lab dishes match what happens in human patients, and that omicron’s mutations actually influence the severity of infection.

Data from South Africa, England and other countries suggest that omicron infections might be less severe, on average, but background levels of immunity from natural infection and vaccination make these results tricky to interpret, NPR reported.

Omicron has more than 30 mutations in the genes that code for its spike protein, the part of the virus that plugs into cells to trigger infection, Live Science previously reported. Of those, 10 code for parts of the “receptor binding domain” (RBD), or the specific portion of the spike protein that latches onto cells. 

To probe how these spike mutations might change how the virus interacts with cells, the researchers engineered synthetic viruses, called pseudoviruses, that carry the omicron spike protein. For comparison, they also generated pseudoviruses with the delta spike protein and some with the Wuhan-1 spike, or that of the original SARS-CoV-2 virus.

The team wanted to understand how three omicron-specific mutations in the so-called polybasic cleavage site (PBCS) affect the virus’s ability to enter cells. After the spike protein plugs into a cell, the PBCS cleaves, or splits open, to allow genetic material from the virus to enter the host cell; the alpha and delta variants carry PBCS mutations that help them enter cells more easily, according to a previous study by the researchers, published June 8 in the journal Cell Reports.

Omicron carries similar mutations in its PBCS genes, so the team predicted that it might slip into cells as easily as alpha and delta do. They tested this theory by using their pseudoviruses to infect human lung cells in lab dishes, as well as lung organoids — 3D clusters of cells made to mimic features of full-size lungs. They found that, despite its concerning PBCS mutations, omicron entered the lung cells and organoids less efficiently than delta and instead more closely resembled Wuhan-1.

Delta also outperformed omicron in a second experiment. Upon entering a cell, the delta pseudoviruses triggered cell fusion, a phenomenon that sticks neighboring cells together and allows the virus to quickly spread between them. Widespread cell-cell fusion in the lungs is often seen in the context of severe COVID-19, the researchers noted in their report. However, in their experiments, omicron initiated cell fusion less efficiently than delta, and this seemed to hinder the virus’s ability to replicate in lung cells. 

(A separate study, also not peer reviewed, found that omicron replicated much more efficiently than delta in upper airway cells, but less efficiently than even the original strain of SARS-CoV-2 in lung cells.) 

Related: 20 of the worst epidemics and pandemics in history

“We speculate that the more efficient the virus is at infecting our cells, the more severe the disease might be,” Gupta said in the statement. “The fact that omicron is not so good at entering lung cells and that it causes fewer fused cells with lower infection levels in the lab suggests this new variant may cause less severe lung-associated disease.”

Future studies will need to confirm that these experiments in lab dishes translate to the human body. In the meantime, the team’s experiments with antibodies affirm that to achieve maximum protection against the variant, people should get booster shots ASAP, Gupta said in the statement.

“Individuals who have only received two doses of the vaccine — or worse, none at all — are still at significant risk of COVID-19, and some will develop severe disease,” he said. “The sheer number of new cases we are seeing every day reinforces the need for everyone to get their boosters as quickly as possible.”

Originally published on Live Science.

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US coronavirus: It’s not clear yet if Omicron is a milder variant. But its rapid spread is going to overwhelm hospitals, experts say

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The variant is expected to become the “dominant strain” in the coming weeks, CDC Director Dr. Rochelle Walensky said on Friday.

And after nearly two years of a pandemic that has caused more than 800,000 deaths in the US and overloaded hospitals, the omens aren’t favorable for the next few months, according to experts.

“Even if (Omicron) is less virulent than earlier strains, if we have a point where we’re seeing a half-million cases a day or more, we are going to swamp our hospitals — even with a relatively low rate of hospitalization,” said CNN medical analyst Jonathan Reiner, a professor of medicine and surgery at George Washington School of Medicine & Health Sciences. “When you have that kind of denominator, our hospitals will be completely underwater as they are in some parts of the country,” he said.

Dr. Francis Collins, the director of the National Institutes of Health, said it’s too soon to assume Omicron will cause milder disease.

“It’s clear that Omicron is an extremely contagious variant, that it doubles every two to four days,” Collins told CNN’s Anderson Cooper.

Collins said people can limit the consequences of the variant with vaccines, especially with boosters.

Data from two weeks of South African cases appeared to indicate Omicron was milder in severity. The CDC said last week that it looked at 43 cases and most of those people had mild symptoms. Most were vaccinated, with about a third of the total group boosted.

But, UK epidemiologists said this week they found no evidence that Omicron is causing milder disease there, although the Imperial College London team also said there was not much data to go on yet.

“We still don’t really know — and there’s some controversy about this — whether Omicron causes the same kind of severity of disease or whether it’s a somewhat milder form of the illness,” Collins said.

With a more infectious variant, even if it’s milder, it could still send more people to hospitals.

“The problem, of course, is if this is so infectious — and we might see hundreds of thousands of cases every day, maybe even a million cases in a day from Omicron — even if it’s a little less severe, you are going to have a lot of people in the hospital and our hospitals are already really stretched with Delta, especially in the northern part of the country,” Collins said.

Overall, the US on Friday was averaging 121,707 new Covid-19 cases each day, according to data collected by Johns Hopkins University. Fourteen states saw an uptick of at least 10% in cases over the past week compared to the previous week, the data shows.

Hospitals are already feeling the impact

About 68,900 Americans are hospitalized with Covid-19, according to data from the US Department of Health and Human Services. More than 20% of all ICU beds in use are occupied with Covid-19 patients, the data shows.

California health officials said Friday they were seeing hospitalization numbers begin to trend upward, stressing the need for vaccinations and booster vaccines. In New York, officials said they’re seeing the highest hospitalization rate they’ve recorded in months, with Gov. Kathy Hochul noting that the staff shortages will weigh into potential new restrictions.

On Thursday, New York state had the highest single-day count of new cases with 21,027, according to data released Friday.

Dr. Marc Gorelick, who heads Children’s Minnesota hospital, said the facility is already struggling to cope with the numbers.

“When you’re on top of a surge where you’re already at 90%, 95% capacity, those extra … preventable Covid patients coming in are the thing that pushes the system to the brink. And that’s what we’re seeing here in Minnesota,” Gorelick told CNN’s Kate Bolduan on Friday.

It got so bad that hospital leaders in Minnesota took out a full-page newspaper ad this week to say they were overwhelmed by the pandemic.
“It feels like you are drinking from a fire hose with no way to control that flow,” Dr. John Hick, an emergency physician at Hennepin Healthcare in Minnesota, told reporters Tuesday. “I have been practicing for 25 years in the emergency department, and every shift I am working these days is like the worst shift in my career.”

In Oregon, officials forecast a grim early 2022.

“We can expect a surge in Oregon hospitalizations by mid-January, with infections that begin sooner than that,” said Dr. Peter Graven, a data scientist for Oregon Health and Science University. “Combined with its heightened transmissibility, we expect Omicron will generate a large increase in the number of Oregonians that will become severely ill and likely need a hospital.”

Restrictions are making a swift return in some states

The US has fully vaccinated just over 61% of its total population, with about 29% receiving a booster dose, according to the latest CDC data.

And as Omicron’s spreads, some officials have moved to reinstate restrictions.

In Maryland, Prince George’s County Public Schools will shift to remote learning beginning December 20 through January 18 due to “the stark rise in COVID-19 cases throughout (their) school system,” according to a Friday statement from the school district’s Chief Executive Officer Monica Goldson.

The University of Maryland canceled its winter commencement ceremonies, noting that all social gatherings on campus where mask wearing could not be strictly enforced should follow suit. Final exams will be conducted in person, but students and faculty will be required to wear a university-provided KN95-rated mask, it said.

Michigan State University and New York’s Hofstra University both said Friday that students and staff will be required to have booster shots for start of the spring semesters.

In Hawaii, a ceremony that was slated to celebrate the end of the state’s National Guard’s Joint Task Force on Covid-19 was canceled, and the governor’s office said the task force is being reestablished due to Omicron.

CNN’s Maggie Fox, Deidre McPhillips, Amy Simonson, Leslie Holland, Evan Simko-Bednarski, Laura Studley, Taylor Romine, Kristina Sgueglia, Artemis Moshtaghian and Andy Rose contributed to this report.

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