As millions of Americans travel in the coming days to gather with friends and family, chances are Covid-19 will follow.
Experts expect Thanksgiving gatherings to shake up social networks and give new sub-variants of the coronavirus new groups of vulnerable people to infect. As a result, post-holiday cases and hospitalizations could add up, as they have for the past two years.
Covid-19 is not unique in this. Thanksgiving gatherings have the potential to amplify the spread of other viruses, particularly respiratory syncytial virus, or RSV, and flu, both of which are already at high levels for this time of year.
“We’ve seen RSV numbers start to trend downward in some regions. Flu numbers continue to rise. And we are concerned that after the holiday gathering many people gather, that we will also see an increase in Covid-19 cases,” said Dr. Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention, on CNN Tuesday.
But things are relatively quiet on the Covid-19 front. Experts say it may not stay that way for long.
“Covid positivity is on the rise,” said Shishi Luo, associate director of bioinformatics and infectious diseases at genetic testing company Helix, which monitors coronavirus variants. “It’s increasing fastest among 18 to 24 year olds” in the Helix sampling.
It’s the first time test positivity in the Helix data has risen since July.
When test positivity increases, it means a higher proportion of Covid-19 tests are showing positive results, and it could be an indication that transmission is increasing.
“We should expect more cases,” Luo said. “Whether they are measured in how we measure cases now, I don’t know, but I think in general you should see more people who are sick. I am for sure.’
Rising cases may not be picked up as quickly by official counts because people usually test for Covid-19 at home and don’t report their results – if they test at all.
Omicron’s BQ sub-variants have become a dominant 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 the immunity created by vaccines and infections. Because of these changes, they grow faster than BA.5.
For the week ending Nov. 19, the CDC estimates that BQ.1 and BQ.1.1 caused about half of all new Covid-19 cases in the US. But so far they have prevailed without much impact.
Covid-19 cases, hospitalizations and deaths have remained flat over the past four weeks. But it’s not gone: On average, more than 300 Americans die and 3,400 people are hospitalized with Covid-19 every day, according to CDC data.
Nobody knows exactly what will happen to the BQ variants. Many experts say they are hopeful that we won’t see the big waves of past winters – certainly not like the original Omicron variant, with its staggering peak of nearly a million new infections daily.
There is reason for optimism on a number of fronts.
First, there is the experience of other countries, such as the UK, where BQ.1 has surpassed its rivals to dominate transmission even as cases, hospitalizations and deaths have fallen. Something similar 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.
“The number of cases went up in France and Germany just before the sub-variants came in. Then the sub-variants came in and the number of cases actually went down,” he said.
Bill Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health, thinks our behaviors and social connections may be a bigger determinant of whether cases will rise this round than any variant leading the way.
He thinks it’s likely we’ll see an increase in cases peaking around the second week of January – as it has in recent years – but that it won’t have a major effect on hospitalizations and deaths.
Andrew Pekosz, a virologist at the Johns Hopkins Bloomberg School of Public Health, says this is likely because BQ.1’s benefits are incremental, not drastic.
“It probably has a little bit more of a fitness benefit, so what we’re seeing is a gradual replacement without a huge change in the overall number of Covid-19 cases,” he said.
That is not to say that BQ.1 and BQ.1.1 will not have any impact. They have shown clear resistance to the antibodies available to protect and treat people vulnerable to serious Covid-19 infections. From that point of view, there is good reason for people to be careful if they have a weakened immune system or will be around someone who does.
But these sub-variants will land at a time when population immunity is greater than ever, thanks to vaccines and infections. It’s a very different setting than the virus we encountered when Omicron emerged a year ago, and that should also help dampen a wave to come, Pekosz says.
“Now that a lot of people are getting boosted and vaccinated and people have some immunity to an Omicron infection, it’s also a very, very different kind of population landscape where a variant is emerging,” he said. “All the signs are, I think, the best part of the scenario in terms of not seeing this massive increase in cases.”
If there’s any reason to be concerned about BQ in the US, it could be this: Americans are not as well vaccinated or stimulated as other countries. CDC data shows that two-thirds of the population have completed the primary series of the Covid-19 vaccines and only 11% of those eligible have received an updated bivalent booster. In the UK, 89% of the population over the age of 12 have completed their primary series and 70% have been boosted.
New research indicates that a country’s vaccination rate is more important than any other factor when it comes to the effects of variants on a population.
Scientists at Los Alamos National Labs recently completed a study into what caused the effects of 13 dominant variants of the coronavirus as they transitioned from one to the other in 213 countries. The study includes data up to the end of September and was published as a preprint ahead of peer review.
Of the 14 variables that influenced the speed and height of new Covid-19 waves, the vaccination rate of a population 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 the age of 65 came in a distant second, third, fourth and fifth respectively.
How many other variants are in the mix when a new one emerges is also an important factor, says senior study author Bette Korber, a lab associate in the Theoretical Biology and Biophysics Group at Los Alamos.
She points out 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 it was much slower in America,” Korber said.
By the time Alpha reached the United States, we were developing our own variants from California and New York “that were very distinctive and had a competitive advantage compared to what it faced in England,” Korber said, which likely slowed its role here.
The CDC is tracking a soup of more than a dozen Omicron subvarieties causing cases in the U.S., and that variety may ultimately help dampen any wave during the winter.
But Korber doesn’t make predictions. She says it’s just too hard to know what’s going to happen, pointing to Asia as the source of her uncertainty.
Asian countries are battling waves driven by the recombinant XBB, a sub-variant that hasn’t really been present in the US. The BQ variants arrived later, but she says they look impressive against XBB, which is also highly immune evasive.
“BQ is really taking a stand on that,” Korber said. “So I guess it can’t really be certain yet” what could happen in the US.
“For me, it’s a good time to wear masks whenever possible,” she said. Masks protect both the wearer and others around them. “And get the booster if you qualify and it’s the right time for you,” especially when we gather around the table to feast with our friends and family.
“It’s a time to take a little extra caution to avoid that wave that we don’t want to see, or at least make it a smaller bump,” Korber said.