How Bad Are COVID, Flu and RSV This Winter?
COVID levels may have peaked but flu is still high; RSV is on the way out
If it seems like almost everyone you know is getting sick with influenza or some other virus right now, it’s not your imagination. The Northern Hemisphere’s respiratory illness season, which typically runs from October to May, is in full swing. Flu hospitalizations appear to have declined from an initial peak in January, but they remain high, and cases may be rebounding. Levels of the virus that causes COVID detected in wastewater are also high and may be rebounding. And respiratory syncytial virus (RSV) is still putting people in the hospital, albeit at lower levels than flu or COVID. Yet despite all the sniffles, it’s shaping up to be a fairly typical year for respiratory viruses.
So far, this year’s flu season looks pretty similar to that of previous years—with the exception of 2020–2021, when flu all but disappeared because of COVID-related masking and social distancing measures. This season’s weekly hospitalization rate reached a peak around January 4 and then appeared to decline, though the Centers for Disease Control and Prevention indicated there may be possible delays in reporting. The latest positive test rate data (some of which were released several days late under the new presidential administration) show a slight rebound in infections, so we may not be out of the woods. There have been some reports that this year’s flu vaccine might be less effective than in previous years, which could explain the apparent high levels of sickness that are currently around. But this season doesn’t seem to be particularly more severe than others.
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To prevent becoming seriously ill with flu, health officials still recommend getting the flu vaccine if you haven’t already, especially if you are age 65 or older or have underlying health conditions. Masking, avoiding crowds and being in well-ventilated spaces are always helpful at reducing the chance of getting infected. And if you should test positive for flu, antiviral drugs such as Tamiflu are available by prescription.
The fact that this year’s season started slightly later than last year’s is a relief, Nuzzo says, in light of the ongoing H5N1 avian influenza outbreaks in cows and poultry that have caused 67 human infections and one death in the U.S. Nuzzo is worried about people getting infected with both H5N1 and seasonal flu—a situation that could increase the risk of bird flu adapting to humans and becoming a pandemic. “I’m a bit relieved because I was fretting about the co-occurrence of H5N1 and seasonal influenza,” she says. “I’m worried about humans getting infected with both viruses.”
There has been a much smaller spike in COVID hospitalizations this winter, compared with previous ones. That’s likely thanks to widespread immunity from vaccination or infection, or both. The U.S. also had a substantial late summer COVID spike in 2024, so some of the immunity from infections during that time may have prevented a large winter surge.
COVID hasn’t really settled into a seasonal pattern like flu and RSV. It seems to peak at least twice a year, including during the summer, which suggests that transmission may be driven at least as much by human behavior as by weather or other environmental factors. “Some of it is our behavior. Some is just opportunity—sort of like Boggle,” Nuzzo says. “Each season you shake up the cubes” and see what happens.
The COVID vaccine is still the best way to protect against severe illness, and most experts recommend that at least older adults and those who are immunocompromised stay up to date on the shot. For those who get COVID and are at high risk of severe disease, experts recommend the antiviral medication Paxlovid—as long as you can start taking it within the first five days after symptoms appear. Studies suggest it offers less benefit for people who aren’t at high risk, however, and it can interact with many other common medications, so seek medical advice if you’re unsure.
COVID still kills more people overall each year than the flu, although flu hospitalizations this winter are double those for COVID, suggesting that flu has had a more concentrated winter peak. It’s not clear whether SARS-CoV-2 will eventually evolve to be less severe than flu virus. “We can’t say definitively ‘no,’” Nuzzo says. “Generally speaking, as a population, we are less susceptible to severe COVID-19 disease. But never say never. I’ve been humbled by this virus several times.”
Like flu, RSV is having a fairly typical year. Hospitalizations appear to have already hit a high mark for the season and are on the way down. “This year is not too bad. Many people think we’re at the peak” of RSV infections, says Peter Chin-Hong, a professor and associate dean for regional campuses at the University of California, San Francisco, School of Medicine.
During the COVID pandemic, RSV showed a slightly odd pattern: like flu, it basically disappeared in the 2020–2021 season, likely because of masking and social distancing. But in 2022–2023 it came roaring back and had a large, early peak during the fall. Last year saw a significant surge as well, but it was closer to the timing of a typical season.
Chin-Hong thinks this year’s somewhat milder RSV season may be the result of the virus settling back into a normal pattern. Also, in 2023 RSV vaccines for older adults and pregnant people were finally approved, and that may have protected more individuals. “There’s still a lot of room to [vaccinate] the older population,” Chin-Hong says. In addition, there’s now a prophylactic antibody drug available to protect young children and newborns from RSV, and uptake of that has been pretty good, he adds.
Flu, COVID and RSV aren’t the only nasty bugs that are circulating, of course. This season has seen one of the worst outbreaks of norovirus—a nasty gastrointestinal pathogen that causes symptoms similar to food poisoning—in the past decade. Between August 1, 2024, and January 15, 2025, there were more than 1,000 norovirus outbreaks reported in the U.S. By contrast, last season there were only about 550 during the same time period.
The likely reason for this surge is that the virus has mutated to a form that fewer people have immunity to. “Outbreaks usually happen when the virus has evolved and population immunity is low,” Jetelina says.This season nearly 70 percent of norovirus outbreaks have been caused by an atypical variant of norovirus, she says.
Then there’s human metapneumovirus (HMPV). In early January a flurry of news reports said HMPV cases were surging in some countries in Asia—but this isn’t a new virus, and experts say it doesn’t pose a major threat. Positive HMPV tests in the U.S. showed a slight uptick in January, but that appears to have subsided.
And of course, at any given time there’s a veritable stew of common cold viruses going around. These include rhinoviruses, adenoviruses and seasonal coronaviruses. Such viruses don’t usually send people to the hospital, but they can make you feel crummy. Most cases can be treated at home with hydration and rest.
As always, it’s a good idea to stay home if you’re not feeling well (and can afford to). Limiting contact with others or wearing a mask can help limit the spread. And washing your hands with soap and water is important, especially for norovirus, because hand sanitizer doesn’t kill the virus.
Editor’s Note (2/5/25): This story has been updated based on the latest COVID wastewater data.
Tanya Lewis is a senior editor covering health and medicine at Scientific American. She writes and edits stories for the website and print magazine on topics ranging from COVID to organ transplants. She also appears on Scientific American‘s podcast Science, Quickly and writes Scientific American‘s weekly Health & Biology newsletter. She has held a number of positions over her eight years at Scientific American, including health editor, assistant news editor and associate editor at Scientific American Mind. Previously, she has written for outlets that include Insider, Wired, Science News, and others. She has a degree in biomedical engineering from Brown University and one in science communication from the University of California, Santa Cruz. Follow her on Bluesky @tanyalewis.bsky.social
Source: www.scientificamerican.com