COVID’s End-of-Year Surprise

The twinkling of lit-up trees and festive displays in store windows have come to mean two things: The holidays are upon us, and so is COVID. Since the pandemic began, the week between Christmas and New Year’s has coincided with the dreaded “winter wave.” During that dark period, cases have reliably surged after rising throughout the fall. The holiday season in 2020 and 2021 marked the two biggest COVID peaks to date, with major spikes in infections that also led to hospitalizations and deaths.

But something weird is happening this year. From September through November, levels of the virus in wastewater, one of the most reliable metrics now that cases are no longer tracked, were unusually low. At various points over that span, hospitalizations and deaths also neared all-time lows.

That’s not to say we are in for a COVID-less Christmas. CDC data released over the past two weeks show a sharp increase of viral activity in wastewater. Whether this is the start of a winter wave still remains unclear, but even if so, the timing is all off. Last year, the winter wave was nearing its peak at Christmas. This time around, the wave—if there is one—is only just getting started. America is in for the most unpredictable COVID holiday season yet.

An optimistic view is that the uptick in wastewater levels reflects the spread that happened over the Thanksgiving holiday and will fall quickly, Michael Hoerger, a Tulane University professor who runs the Pandemic Mitigation Collaborative, a COVID-forecasting dashboard, told me. This is a possibility because the CDC posts wastewater data about a week after they’re collected; the most recent data represent the two weeks after the holiday, which would give people who were infected over the break some time to show symptoms. The worst-case scenario is that low transmission throughout autumn was sheer luck, and over the next few weeks the virus will rapidly play catch-up. Hoerger expects transmission to steadily increase over the next couple of weeks, potentially reaching a zenith around January 7, though a marked increase or decrease remains “plausible,” he said. Even if a wave is around the corner, “it likely will not be anywhere close to any of the peaks we had during the pandemic,” Michael Osterholm, an epidemiologist at the University of Minnesota, told me.

The confusion about how the virus will behave over the holidays reflects a bigger COVID uncertainty: Even after four straight winter waves, experts are torn on whether we should continue to expect them. Caitlin Rivers, an epidemiologist at Johns Hopkins, told me it would be “very unusual” if a wave didn’t happen, given that the virus has generally followed a reliable pattern of peaking in the summer and winter. But Osterholm rejects the idea that the virus follows predictable patterns. The nine peaks that have occurred since COVID emerged “were not predicted at all by season,” he told me. Winter waves have less to do with winter, Osterholm said, and more to do with the unpredictable emergence of new variants overlaid on waning immunity.

Squaring the notion that COVID doesn’t follow seasonal patterns with its recent track record of ruining the holidays is not easy. Part of the confusion stems from the expectation that the virus should behave like other respiratory-season bugs: The flu and respiratory syncytial virus, or RSV, typically spike in the winter, which is why shots are offered in the fall. But as my colleague Katherine J. Wu has written, SARS-CoV-2 is not a typical respiratory-season virus, even though updated COVID vaccines are recommended in advance of the winter virus season. As expected, flu and RSV are currently on the rise. In a way, COVID’s weird timing this year is fortuitous because it means the “peak season will likely be out of sync with flu,” reducing the burden on hospitals, Rivers said.

After nearly five years of living with this virus, you might expect that its behavior would be easier to predict. But in scientific terms, five years is not a long time. COVID may turn out to spike every winter, but it is too early to tell. “The only thing that makes this virus seasonal is that it occurs in all seasons,” Osterholm said. Any patterns that have emerged in that period could be rendered obsolete as more data are collected. In time, the ebbs and flows that have been interpreted as trends may yet prove to be irregularities in a completely different pattern—something “funky,” like having two small waves and a big one each year, Hoerger said.

Try as we might, predicting COVID is a guessing game at best. As the holidays draw near, the present reality offers both a warning and a reason for hope. Another wave could be upon us, but things seem unlikely to unfold the same way they have in years past—when the virus spiked at what should be the most festive time of the year. This won’t be a COVID-free Christmas, but it’s still something to be grateful for.