BA.2, where are you? Dominant strain hasn’t shown signs of starting a surge

Even though BA.2 has become dominant, the total number of cases continues to decline, says Dr. Jessica Justman, an epidemiologist at Columbia University’s Mailman School of Public Health.

“This is a clear example of how these two trends are not necessarily linked,” she says.

That’s different from what’s happening in the UK, some European countries and parts of Canada, where the arrival of BA.2 coincided with a new wave of cases and hospitalizations.

Andy Pekosz, who studies viruses at Johns Hopkins University, says the new wave of cases in Europe may have more to do with timing than with the characteristics of BA.2.

“What you are seeing in Europe may be due to the fact that they lifted their restrictions early, not so much that it is BA.2 that is there,” he says.

Pekosz says that many European countries abandoned some precautions when there were already many viruses circulating. He says cases in the US were declining faster and farther before BA.2 overtook its Omicron cousin here.

“When you start low, it takes a lot longer to build up a large number of cases,” he says.

It also suggests that the US may not be completely out of the woods with BA.2, as spring break and the Easter and Passover holidays will mean more travel and more mixing of people from different parts of the country.

Small sign of increased infections

Why the US is not seeing the same increases in new BA.2 infections as countries in Europe remains an open question.

One theory is that we no longer see positive cases in testing. The data collected by the CDC and state health departments on positive tests is generated by laboratories; it does not count the tests that people take at home.

And there has been a “dramatic shift” toward home testing in the US, says Mara Aspinall, a professor at Arizona State University who has been estimating home and lab testing volumes.

In January and February, he says, there were roughly 1 million to 1.5 million lab tests for Covid-19 each day, but 6 to 8 million home tests were available. A case detected by a home test is usually not reported unless later confirmed by a laboratory test.

“I think there is no question that there is an underreporting of positive cases,” Aspinall said. She believes this is, in part, why the CDC shifted its pandemic measures to focus on hospitalizations and hospital capacity, and focused its surveillance on sewage, which measures infection levels even when people don’t they take the test.

watching sewage

However, even in the sewage, there is not much to see.

Zooming in on areas of the country that are experiencing increased transmission of BA.2, such as New York, sewage has only been modestly affected.

“It’s still low when we look at raw absolute numbers of viral copies in wastewater,” said David Larson, an associate professor of public health at Syracuse University, who helped create the state’s wastewater dashboard.
Wastewater monitoring for Covid-19 is gathering steam in the US.

“We are not at the level of the Omicron [BA.1] increasing, but it’s increasing, and community spread is present, and transmission is still high,” Larson said.

With more viruses being transmitted, Larson says, officials could see an increase in cases, but he’s not sure. He will depend on how sick people get from their infections.

“Cases measure access to treatment and access to testing,” he said. “So it’s hard to say what the cases will do.”

San Francisco is also seeing signs that BA.2 may be making a move, but it hasn’t been a major one.

Dr. Peter Chin-Hong, an infectious disease specialist at the University of California, San Francisco, says the Bay Area has been one of the most cautious parts of the country during the pandemic. There are even some schools that are still closed because they are not willing to tolerate the risk.

He was surprised to see that San Francisco County recently ranked first for its seven-day average of new cases on the California Department of Public Health’s Covid dashboard.

“I had to rub my eyes,” Chin-Hong said. “I see these trends almost every day, and SF used to be at the bottom, and now it’s at the top” in terms of new cases. The positivity of the test is also slowly increasing.

Covid-19 Hospitalizations Hit Pandemic Low in US, But Strain on Hospitals Remains

But the increases you are seeing are small. “They’re teetering on the brink of going up and they like to try to push themselves forward,” she said.

Chin-Hong says San Francisco is “super immune” right now, with one of the highest vaccination rates in the country and a surge in antibodies from the recent wave of Omicron BA.1 infections.

At the hospital where he works, things are calm regarding Covid-19.

It reminds him of what happened in Denmark and South Africa with BA.2, “which was basically nothing. There were no explosions of cases, no lives were lost.”

That won’t stop people from feeling anxious, he said. As cases rise, people will stay home and keep their children from going to school.

He says the anxiety stems from two things: PTSD from previous waves, and a measure of freedom they don’t want to give up.

And while he’s not ready to give the go-ahead, he thinks things may be better than people expect this time.

Are we failing up?

If BA.2 works silently, it may be because the US did such a poor job of stopping the transmission of Omicron and the variants that preceded it, that we have failed upwards, awkwardly, on our way to a high level of immune protection. .

BA.1 and BA 1.1 proliferated in the US over the winter as people ditched mask-wearing and largely resumed their vacation plans.

“That increase was huge. It’s unlike anything we’ve seen before,” says Marina Matus, president and CEO of Biobot Analytics, a company that has been analyzing wastewater from local counties and other sewer basins in the US. US since 2020.

Matus says that Omicron and Delta wiped out the population in a matter of weeks, while BA.2 has been inching for a few months.

“It’s gone very, very slowly, and so far we haven’t seen an impact on the level of the disease,” he said.

Matus points to Ontario, which is experiencing higher viral load levels in its wastewater, indicating more infections. The Omicron spike from that province with BA.1 a few months ago was not as high as the one in the US and may not have left as much immunity in its wake.

“That data, to me, would say that, you know, they had a smaller Omicron wave, and now [BA.2 is] picking up,” he said.

The latest estimate from the CDC is that 95% of Americans have some level of immunity, either from infection or from vaccination. About 43% of Americans are thought to have antibodies to the infection.

This immunity came at a high price: The United States remains the world leader in Covid-19 deaths with more than 980,000, according to data from Johns Hopkins University.

Remembering this makes any respite from Covid-19 over the next few weeks a bit bittersweet. It may also be brief, as the world waits to see what other surprises the virus has in store.

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