As the Omicron wave subsided in the United States earlier this year, many experts anticipated a kind of reprieve. We certainly weren’t done with Covid, but we might get some well deserved rest.
This break seems to be over.
A rise in infections that started in places like the Northeast and Puerto Rico is now being seen in other parts of the country. Cases will rise and fall in the future, but more worryingly, hospitalizations have also started to rise – up to 20% over two weeks. The drop in deaths has bottomed out at around 350 a day.
Epidemiologist David Dowdy of the Bloomberg School of Public Health at Johns Hopkins said that despite the increase in cases, overall hospitalization and death rates remain relatively low compared to previous periods of the pandemic – a reflection of the level of immunity of the population.
“In some ways it’s encouraging, in that we’re starting to see a discrepancy between the number of cases and the number of hospitalizations and deaths,” Dowdy said. “But it’s also a bit disheartening that we’ve been through all of this and still see a flat line and an increase in people being admitted to hospital and people dying.”
To be sure, the United States is currently at a radically different stage of the pandemic than in previous periods. Even though cases have been rising – to 80,000 a day, from less than 30,000 at the end of March – they are still well below the highs of earlier this year and have started to rise from very low levels. Vaccinations, and particularly boosters, continue to provide broad protection against the worst consequences of Covid-19, even as the virus continues to evolve. The growing availability of the antiviral drug Paxlovid is helping to prevent those at risk from getting so sick they need to be hospitalized. Most people have at least some level of protection against Covid-19 – against vaccination, previous infection or both – which means that cases, as Dowdy noted, are less and less likely to lead to serious results .
And yet, if there are more cases overall, some will still lead to hospitalizations and deaths, even at lower rates than before.
There are a range of factors that contribute to the rise and fall of cases, including climate, behavior and mitigation efforts (or lack thereof). Scientists are trying to focus on what the latest surge in cases says about the durability of protection and the continued evolution of the virus.
People can become susceptible to infection again if their immunity wanes or the virus mutates in a way that allows it to sneak past the body’s defensive recognition systems. Experts analyzing current patterns of epidemics believe that both factors could be at play: it seems that if protection against serious diseases holds up well, the ability to block an infection diminishes within months. And while the first Omicron wave was led by the BA.1 subline, the current peak in the cases is widely BA.2, and increasingly, a derivative called BA.2.12.1. These variants are not only more efficient propagators than BA.1, but they might also appear distinct enough from past forms of the virus to be able to evade people’s immunity and trigger infections.
“Why is this happening?” said Jacob Lemieux, an infectious disease physician at Massachusetts General Hospital, who has tracked the variants. Are the new variants so different, or is the immunity so transient? “We don’t know, but it raises a lot of really important scientific questions,” Lemieux said.
Answering such questions could help shape our understanding of what our relationship with the SARS-CoV-2 virus will look like in the future. Could this mean, for example, that communities become susceptible to new outbreaks after only a few months, especially with the emergence of a new mutated virus?
Evidence for this hypothesis does not come only from the United States. South Africa suffered a major wave of BA.1 and is now experiencing a new wave of cases (and to a much lesser extent hospitalizations) from other Omicron sublines, BA.4 and BA.5 .
The current infection peaks are different in other ways from previous waves. While these were driven by entirely new variants that emerged from distant points on the SARS-2 family tree, now different branches of Omicron are triggering new outbreaks. This “genetic drift” is closer to the evolution of influenza strains.
“Maybe what we’ll see will be these waves of subvariants,” said Jonathan Abraham, assistant professor of microbiology at Harvard Medical School.
To complicate matters, the data that scientists rely on to analyze outbreaks is increasingly messy. The official case count misses more infections because testing programs are canceled, people rely on home testing, or they have cases so mild they don’t bother to get tested.
Even the data on hospitalizations is fuzzy. As the prevalence of the virus increases in communities, some people who go to hospital for, say, surgery, could test positive for SARS-2 and appear in official counts. Some states track who is hospitalized for Covid-19, versus who happens to be hospitalized with Covid19. the Massachusetts Dashboard, for example, notes that about 1 in 3 patients counted were “hospitalized primarily for illness related to Covid-19”. (An additional wrinkle: even if someone is hospitalized due to complications from a chronic illness, it’s possible that Covid has exacerbated it to the point that they need to be admitted.)
Global health officials also warn of the risk of reduced surveillance efforts. Some of the systems that were put in place to test and sequence the virus have begun to weaken, which scientists say leaves the world with less understanding of how the virus mutates and what threats these changes could pose. to pose.
“Our ability to detect this is significantly hampered as testing rates have dropped, and in doing so our sequencing rates have also dropped,” Maria Van Kerkhove, the World Health Organization’s technical lead for Covid-19, said on Tuesday. 19, about BA. 4 and BA.5, noting that only a few hundred sequences of each have been shared.
It appears, Van Kerkhove said, that BA.4 and BA.5 are capable of outperforming BA.2, but it is unclear whether countries that have BA.2 waves will be vulnerable to BA.4 waves and BA.4. So far, it does not appear that any of the Omicron lines cause more severe disease on average than BA.1.
One of the reasons experts anticipated a break this spring is because so many millions of people in the United States were infected during its BA.1 wave. But recent studies in South Africa and elsewhere have found that a BA.1 infection alone does not provide much cross-protection against other variants – meaning that people might not be able to resist an infection from another Omicron subline. The combination of vaccination and BA.1 infection, however, provided broader and more robust protection.
Melanie Ott, a virologist at the Gladstone Institutes, said what’s happening now could be a glimpse of what’s to come. One variant begins to circulate, causes an increase in the number of cases, and then is overtaken by another variant which may outcompete it, presumably because it is more effective at causing infections in those protected. Such a pattern might look different from place to place.
“The virus does what viruses do, and it adapts to a changing immune landscape,” Ott said.