Covid’s winter surge is poised to exceed summer peak

The number of people in the United States hospitalized with Covid-19 is about to surpass the figure reached during this summer’s spike, federal data show, as a confluence of factors — from the continued evolution of the coronavirus to holiday gatherings — drives transmission.

Notably, the number of people hospitalized with Covid — roughly 40,000 — is still far below the winter waves of 2020-2021 and 2021-2022 (the wave driven by the original Omicron variant) as well as the Delta wave in summer and fall 2021. But it seems clear that the anticipated winter wave has begun, at least in parts of the country.

Hospitalizations among people 60 and older — those most vulnerable to severe outcomes from a Covid case — have been taking off since mid-November, federal data show.

The most recent data may not paint a clear portrait of where the country stands with Covid. Reporting often gets delayed over the holidays or after severe weather. Average daily deaths, for example, had passed 400 in mid-December after hovering in the 300s for several months, but they’ve since fallen back into the 300s. It’s possible the decline is because of delays in confirming deaths.

Hospitalization data are also more difficult to interpret. With more Covid in the community, more people will test positive even if their admission is not connected to Covid (though it’s possible their infection is exacerbating some preexisting issue, whether diabetes or lung disease). Massachusetts, for example, says that of the 1,149 patients hospitalized with Covid, 361 are hospitalized primarily because of their infection.

Still, it seems clear that Covid is on the rise once again. Part of the increase in transmission could be the growth in prevalence of XBB.1.5, the latest Omicron subvariant to assert itself. Data from the Centers for Disease Control and Prevention released last week indicate the variant is causing some 40% of U.S. infections, and it’s heading toward dominance faster than the most recent titleholders, other forms of Omicron known as the BQs that are now receding. That suggests it has quite a transmission boost.

XBB.1.5 is snowballing because it’s better than its rivals at infiltrating all the layers of immunity people have, from vaccinations (including the original formulation and the updated boosters) and from infections (even if they’ve been infected with earlier forms of Omicron, say BA.2 or BA.5). The takeover by XBB.1.15 is the latest in a passing-the-baton sequence of Omicron variants that rise and fall as the immunity profile of an area changes.

It’s been dizzying to try to keep track of those splintering Omicron lines, and XBB.1.5 itself is a descendant of another Omicron form called XBB. But this go-around, experts say that the latest lineage is likely just one factor in the rising case counts.

First off, it’s the time of the year when we expect respiratory viruses to take off, both because of viral factors (these bugs seem to spread better in colder, drier air) and human behavioral ones (holiday gatherings and travel, more time indoors, etc.).

There’s also the issue of waning immunity: Vaccination or a bout with Covid seems able to prevent infection for only a matter of months in some cases — particularly in the face of an evolving virus. Then there’s the limited uptake of the bivalent booster, with only 17% of adults having received the updated form of the shot despite evidence showing it boosts protection. And there’s the reality that few precautions remain in place to limit transmission of the SARS-CoV-2 virus or other respiratory bugs.

The emergence of XBB.1.5 is not a reset of the pandemic, but rather seems to be a further continuation of most of the past year. Some level of immunity is keeping most people protected from severe outcomes. Lots of people infected now won’t even realize it or will have mild cases (which can still leave people feeling pretty sick for a few days). But even as the percentage of infections that result in severe outcomes drops, if cases skyrocket, there will still be notable increases in hospitalizations and deaths. This will add pressure to health systems that have faced successive, overlapping waves of RSV, then flu, and increasingly Covid.

Even if Covid will be little more than a nuisance for many on an individual level, others who may not realize the virus remains a threat to them — particularly older people — might also be shrugging off the risk amid talk that the pandemic has ended. The low uptake of the latest booster shot — just about one in three seniors have gotten the shot — could be evidence of that.

There are also those who know Covid poses a danger to them — such as people who are immunocompromised — but who are facing a landscape with fewer tools to keep them protected.

Regulators in November pulled the authorization for the last monoclonal antibody treatment, bebtelovimab, as it became clear the therapy wouldn’t work against the latest forms of Omicron. The continued evolution of the virus has also undercut the power of Evusheld, which is given as a precaution to people who struggle to mount an immune response to vaccinations. Other treatments are available, including both oral and intravenous antivirals, but they have limitations as well.

It’s not clear how big the burgeoning winter wave will get, nor is it clear how policymakers will react. New York City Mayor Eric Adams has said people should mask again, and in Boston, where wastewater data show viral levels spiking, officials are asking staff and students in the public school system to wear masks temporarily when they return from break. Los Angeles County officials have also asked people to wear masks for the first 10 days of the new year. But those requests seem to be the exception, as much of the country has put Covid in the rearview mirror.

The Biden administration continues its campaign to increase uptake of the booster shots, particularly among older people, and federal health officials encourage people to wear masks in areas of high transmission. The administration also last month reupped its program of offering free at-home Covid tests through the U.S. Postal Service.

Even as the country has reached what feels like a stasis in its response to Covid, there’s more attention being paid to the explosion of cases in China, as it exits its “zero Covid” policy. Late last month, the United States said it would require all travelers coming from China to provide a negative Covid test.

The fear is that the takeoff in transmission in China could result in a new variant, though experts note there aren’t the levels of population immunity there that would be more likely to drive the virus to mutate into a more immune-evasive form. So far, the sequences that have been made available from China indicate that the spreading viruses are forms of Omicron that have been seen elsewhere, not new forms of the virus.

Still, the World Health Organization on Friday said that officials had met with Chinese authorities and called on them to expand sequencing and share information about that data, as well as to increase uptake of vaccines and boosters.

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