‘Tripledemic’ Rages On: Fever-Filled Weeks Lie Ahead

It has become wearyingly routine: Americans are embarking upon yet another holiday travel season in the midst of a viral onslaught.

New, immune evasive versions of the Omicron variant are spreading, and Covid-19 cases, hospitalizations and deaths are once again rising, although the figures remain far below last winter’s peak. But this year the coronavirus has company: Common seasonal viruses, which lay low for the last two winters, have come roaring back.

“And as it turns out, they have some makeup work to do,” said Peter Graven, who directs the office of advanced analytics at Oregon Health & Science University.

In particular, influenza and R.S.V., or respiratory syncytial virus, hit early and hard this fall, causing major outbreaks that are now overlapping with a resurgent coronavirus. This viral pileup — what some are calling a “tripledemic” — has already set off an exhausting season of sickness, triggering sky-high demand for pain and fever relievers and pushing children’s hospitals to the brink.

But each of these three viruses is on a slightly different trajectory. Although there is considerable geographic variation, in most parts of the country R.S.V. has probably already peaked, while flu is now surging, experts said. And Covid is still ramping up, with cases likely to continue rising.

That means that more difficult, fever-filled weeks still lie ahead. “A lot of sniffly kids,” said Andrew Lover, an infectious disease epidemiologist at the UMass Amherst School of Public Health and Health Sciences. “There’ll be a lot of respiratory illness floating around from all these different sources.”

It is not too late to get a Covid booster or a flu shot, which appears to be well-matched to the influenza strains circulating this year, scientists said. And experts repeated their now-common exhortations to take basic precautions, such as wearing masks in crowded indoor spaces, using rapid Covid tests before visiting vulnerable people and staying home when feeling unwell.

“I know people are kind of tired of hearing some of that stuff,” Dr. Graven said. “We’re not saying people need to change your life forever. Right now, for the next some number of weeks, we’re in not a great spot.”

Scientists are hopeful that next winter will be better, noting that this brutal season is an unfortunate, and not entirely unexpected, byproduct of several years of pandemic precautions, such as masking and social distancing. These measures shielded many people from routine winter infections and may have spared overburdened health care systems from even bigger surges.

But many children and adults also missed out on the opportunity to build or bolster their immune defenses against flu and R.S.V., leaving the viruses with an unusually vulnerable population this fall.

“There was a bit of a buildup of susceptibility at the population level,” said Virginia Pitzer, an infectious disease epidemiologist at the Yale School of Public Health. “It’s a worse than normal winter, but one that hopefully will not be repeated next year.”

A viral comeback

The first virus to surge this fall was R.S.V., which usually causes mild illness but can be severe, or even fatal, in older adults and young children. By the time children in the United States are two years old, almost all have been exposed to the virus.

The virus typically peaks in December or January. But this year, cases of R.S.V. began rising steeply in September, and by mid-November, pediatric hospitalization rates had hit the highest level since tracking began in 2018. Hospitalization rates for older adults have surged, too.

Flu took off in October, about six weeks ahead of schedule, and has already caused at least 150,000 hospitalizations and 9,300 deaths, according to estimates from the Centers for Disease Control and Prevention. The cumulative hospitalization rate is higher for this time of year than it has been in more than a decade.

“We had a huge pool of people, compared to what we normally do, who could be infected by R.S.V. and could be infected by flu because we’ve basically missed two seasons of it,” said Jeffrey Shaman, an infectious disease epidemiologist at Columbia University. As a result, he said, the viruses were “able to go to work early and infect a lot of people. And that’s why we’re seeing these very large, marked outbreaks early on.”

There have also been reports that cases of invasive infections of group A Streptococcus bacteria, or strep A, may be on the rise in the United States and Europe. Although these cases remain rare, they may be related to the recent surges in flu and R.S.V., which can leave people more vulnerable to invasive strep, officials have said.

However, some encouraging signs have recently emerged, especially regarding R.S.V. Nationally, hospitalization rates and R.S.V. detections have fallen since mid-November, according to C.D.C. data.

“I think it’s likely that the R.S.V. season has peaked in most parts of the country,” Dr. Pitzer said. “I think that there is a light at the end of the tunnel.”

The trajectory of the flu surge is more difficult to discern, scientists said. Levels of the virus are still very high, and some locations may be seeing their flu peaks now. “It still looks really serious most everywhere,” Dr. Lover said.

But there are hints that conditions may be beginning to improve in some areas of the country, including in parts of the South and the Mid-Atlantic States. According to the C.D.C.’s latest influenza report, during the week that ended on Dec. 10, the percentage of laboratory samples testing positive for flu held steady, nationally, and the number of hospital admissions declined, compared with that of the previous week.

Several experts expressed hope that this year’s early-starting flu season might also end early, with cases plummeting quickly as the virus finds fewer people to infect. “It burns through all the people who are susceptible to disease or to infection and doesn’t have as much fuel during the traditional season,” said Justin Lessler, an infectious disease epidemiologist at the University of North Carolina at Chapel Hill.

Earlier this year, for instance, Australia saw a severe, early flu season, with cases rising precipitously and then “crashing down pretty quickly,” Dr. Shaman noted.

Alternatively, flu cases could plateau for a while. In a number of California communities, the amount of influenza present in the wastewater has stopped rising but remains high, said Alexandria Boehm, an environmental engineer at Stanford University and a lead investigator for WastewaterSCAN, a national sewage surveillance initiative. “That suggests that there are still quite a few infections,” she said.

Even if the current outbreak abates, another flu bump could occur later in the season, scientists said.

“The optimistic view is that we had an early, severe season, and that hopefully what will happen over the next couple of weeks is that all of the numbers will start going down,” said Dr. Helen Chu, an infectious-disease physician and epidemiologist at the University of Washington. “But the pessimistic view is that this is just the beginning, and then we’ll see a couple of later waves.”

Covid, again

Covid-19, on the other hand, appears to be on the upswing. At many of WastewaterSCAN’s sites, coronavirus levels began increasing in early November and surged around Thanksgiving, Dr. Boehm said. Levels are still trending upward at most sites, she said; at some, they are even approaching last winter’s peaks.

Officially recorded Covid cases, which remain a significant underestimate, have increased 24 percent over the past two weeks, while hospitalizations are up nine percent. There are more than 400 Covid-related deaths a day, on average, a 41 percent jump from two weeks ago.

Those figures are likely to rise further in the coming weeks, experts predicted, fueled by a combination of holiday travel, indoor gatherings, waning immunity and the spread of BQ.1 and BQ.1.1, two new, highly immune-evasive versions of Omicron. (So far, these subvariants do not appear to be causing more severe disease than earlier forms of Omicron did, scientists said.)

The precise timing and size of a new Covid wave is difficult to predict, with experts forecasting that cases might peak nationally anytime between the end of December and early February. Most predicted that high levels of pre-existing immunity — from vaccination, infection or both — would likely keep the overall toll lower than during previous winter surges.

“We’re going to get a noticeable and meaningful peak in hospitalizations and deaths but nothing that looks like what we saw the past two winters,” Dr. Lessler said.

The emergence of new variants remains a wild card. The explosion of cases in China could theoretically increase that risk; the more the virus spreads, the more opportunities it has to mutate and evolve. But new variants can emerge anywhere, and given how widespread the virus already is around the world, China’s current outbreak may not have “an appreciable impact on the rate at which new variants are emerging,” Dr. Lessler said.

It remains too early to say whether flu and R.S.V. will return to their typical rhythms next year. But not every winter will be this bad, scientists predicted. “We are sort of making up for the immunity gap that existed during these last two years,” Dr. Chu said. “Things will probably get better.” (An R.S.V. vaccine might be available by next winter, too, she noted.)

Still, even before the pandemic, the flu burden varied widely from year to year — a bad season can cause more than 50,000 deaths and overwhelm hospitals — and Covid is likely to remain part of the winter mix.

“That’s going to run up the numbers every year, in terms of how many people have severe respiratory disease,” Dr. Lessler said. “I wouldn’t be surprised if just the overall burden from severe respiratory disease is going to be higher in the coming decade than it was in the decade leading up to 2020.”