New sub-variants, family reunions could bring more Covid-19 after holiday, but experts don’t expect a sharp increase



CNN

With millions of Americans traveling over the next few days to meet up with friends and family, there’s a good chance Covid-19 will follow.

Experts predict Thanksgiving gatherings will stir up social media and give new coronavirus subvariants new pockets of vulnerable people to infect. As a result, post-holiday cases and hospitalizations may surge as they have over the past two years.

Covid-19 is not an isolated case in this respect. Thanksgiving gatherings have the potential to amplify the spread of other viruses as well, most notably respiratory syncytial virus, or RSV, and influenza, both of which are already at high levels this time of year.

“We have seen in some regions that RSV numbers are trending downwards. The flu numbers continue to rise. And we are concerned that after the holiday gathering many people will come together and we may also see an increase in Covid-19 cases,” said Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention, on CNN on Tuesday.

Things have been relatively calm on the Covid-19 front, however. Experts say it won’t stay that way for long.

“Covid positivity is increasing,” said Shishi Luo, deputy director of bioinformatics and infectious diseases at genetic testing company Helix, which monitors coronavirus variants. “It gains weight fastest among 18- to 24-year-olds” in the Helix sample.

It’s the first time since July that test positivity has risen in the Helix data.

If test positivity increases, it means a larger proportion of Covid-19 tests are giving positive results and this may be an indication that transmission is increasing.

“We should expect more cases,” Luo said. “Whether they’ll be measured the way we currently measure cases I don’t know, but I think in general you should be seeing more sick people. I definitely am.”

Increasing cases may not be captured as quickly by official counts as people mainly test for Covid-19 at home and don’t report their results – if they test at all.

Omicron’s BQ subvariants have risen to dominate transmission in the US. BQ.1 and its offshoot BQ.1.1 are descendants of BA.5; They have five and six key mutations in their spike proteins, respectively, that help them evade immunity generated by vaccines and infections. Because of these changes, they grow faster than BA.5.

For the week ended November 19, the CDC estimates that BQ.1 and BQ.1.1 caused about half of all new Covid-19 cases in the United States. But so far they have risen to dominance without much impact.

Covid-19 cases, hospitalizations and deaths have remained flat over the past four weeks. But it’s not going away: Every day, on average, more than 300 Americans die and 3,400 people are hospitalized with Covid-19, according to CDC data.

Nobody knows exactly what will happen to the BQ variants. Many experts say they’re hopeful we won’t see the big waves of past winters – certainly nothing like the original Omicron variant, with its staggering peak of nearly a million new infections daily.

There is reason for optimism on several fronts.

First, there is the experience of other countries such as the UK, where BQ.1 has outperformed its rivals to dominate transmission even as cases, hospitalizations and deaths have declined. Similar things happened in France and Germany, notes Michael Osterholm, an infectious disease expert who directs the Center for Infectious Disease Research and Policy at the University of Minnesota.

“Cases emerged in France and Germany just before the sub-variants arrived. Then the subvariants came along, and the cases actually went down,” he said.

Bill Hanage, an epidemiologist at Harvard TH Chan School of Public Health, believes that our behavior and social interactions may be a bigger determinant of whether cases will increase this round than which variant tops.

He thinks it’s likely that we’ll see a spike in cases, which could peak around the second week of January — like in previous years — but that it won’t have a big impact on hospitalizations and deaths.

Andrew Pekosz, a virologist at the Johns Hopkins Bloomberg School of Public Health, says that’s probably because the benefits of BQ.1 are incremental, not drastic.

“It probably has a slightly larger fitness benefit, so we’re seeing a gradual replacement without a massive change in the total number of Covid-19 cases,” he said.

All this is not to say that BQ.1 and BQ.1.1 will not have an impact. They have shown marked resistance to the antibodies that are available to protect and treat people susceptible to severe Covid-19 infection. From this point of view, there is good reason for people to be cautious if they have a compromised immune system or are around someone who does.

But these subvariants will land at a time when population immunity is higher than ever thanks to vaccines and infections. It’s a very different environment than the virus that emerged a year ago when Omicron emerged, and that should also help dampen any surge to come, Pekosz says.

“Now that a lot of people are being boosted and vaccinated, and people have some immunity to omicron infection, it’s also a very, very different type of population landscape that variant can appear in,” he said. “All the signs, in my opinion, are the best part of the scenario when it comes to not seeing this massive increase in cases.”

If there is cause for concern about BQ in the US, it might be this: Americans are not as well vaccinated or fortified as other countries. CDC data shows that two-thirds of the population have completed the first series of Covid-19 vaccines and only 11% of those eligible have received an updated bivalent booster shot. In the UK, 89% of the population over the age of 12 have completed their primary series and 70% have gone on to top up.

New research shows that a country’s immunization coverage accounts for more than any other single factor when considering the impact of variants on a population.

Scientists at Los Alamos National Labs recently completed a study looking at what drives the impact of 13 dominant variants of the coronavirus as they transition from one to another in 213 countries. The study includes data up to the end of September and was published as a preprint prior to peer review.

Among 14 variables affecting the speed and magnitude of new Covid-19 waves, a population’s vaccination rate was by far the most important.

The number of previous cases in a country, the percentage of people wearing masks, the median income and the percentage of the population over 65 ranked second, third, fourth and fifth by a wide margin, respectively.

How many other variants are in the mix when a new one arises is also an important factor, says lead study author Bette Korber, a lab associate in the Theoretical Biology and Biophysics Group at Los Alamos.

It points to the Alpha variant B.1.1.7 and how it behaved in the UK versus the US.

“When it came through England it was just extremely fast, but in America it was a lot slower,” said Korber.

When Alpha reached the United States, we developed our own variants out of California and New York, “which were very distinctive and had a competitive edge over what they had to encounter in England,” said Korber, which likely slowed down his role here .

The CDC is tracking a soup of more than a dozen omicron subvariants causing cases in the US, and this strain could help dampen any winter surge.

But Korber makes no predictions. She says it’s just too difficult to know what’s going to happen, citing Asia as the source of her uncertainty.

Asian countries are grappling with waves fueled by recombinant XBB, a sub-variant that really hasn’t had much of a presence in the US. The BQ variants came later, but she says they look impressive compared to XBB, which is also very immune avoidable.

“BQ is really setting the tone there,” said Korber. “So I think it’s not really possible to be sure yet” of what could happen in the US.

“For me, when it’s possible to wear masks, it’s a good time,” she said. Masks protect both the wearer and others around them. “And get the booster if you’re eligible and it’s the right moment for you,” especially when we gather around the table to feast with our friends and family.

“It’s time to use a little extra caution to prevent this wave that we don’t want to see, or at least make it a smaller bump,” Korber said

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