It's Winter and viruses are running around

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A nationwide surge in flu, COVID-19, RSV and norovirus infections is fueling concerns of a possible virus "quademic." Or is it just winter?

The three respiratory viruses plus norovirus, a gastrointestinal virus, are the "main players in our winter virus pantheon," said Dr. Thomas Russo, who heads the infectious diseases department at the University at Buffalo School of Medicine. Russo added that they can circulate at other times of year but tend to peak in winter.

"Do we have a lot of cases? The answer is yes," Russo told USA TODAY. "The 'emic' part of it is a bit of a gimmick, but we do have these viruses circulating and causing infections right now."

All are not peaking at precisely the same time, but spikes in the viruses are "clustering," said Dr. Ogbonnaya Omenka, director of equitable population health for Humana Indiana Pathways.

"The term (quademic) does not imply a public health doomsday," Omenka said. "We deal with them every year."

A Centers for Disease Control and Prevention flu report for the week of Jan. 25 showed almost 30% of lab tests for flu were positive and the rate was trending higher. There were also 16 deaths related to influenza, bringing the total to 47 deaths this season, according to the report.

RSV numbers appear to have peaked in recent weeks and are dropping. COVID-19 was at a 5.4% test positivity for the week that ended Jan. 25, and 1.6% of all deaths in the U.S. that week were linked to the virus, per CDC data. Russo said COVID-19 numbers appear to be "smoldering" and he expects them to peak in the coming weeks.

"We haven't seen the (COVID) peak we have seen in previous winters," Russo said. "Peaks in RSV and influenza have been greater, and we may see a peak in COVID in upcoming weeks."

Health departments are not required to report norovirus cases to the CDC, but Russo says it's been a "big norovirus year." COVID and norovirus are a problem all year round, although they tend to peak in winter months when people are enclosed indoors in close spaces, he said.

Symptoms can be similar
Russo said it is unlikely that someone would get two of the infections at the same time, and that "to get all four is certainly unlikely, particularly if you are vaccinated." Symptoms can be similar and can include fever, chills, cough, sore throat, runny nose, muscle or body aches, fatigue, headache, vomiting and diarrhea.

Because the viruses share some common characteristics, including symptoms, test results are the only way to know exactly the type of virus involved in each case. But it also means that preventing one may also help prevent all of them, Omenka said. Vaccines are available for the flu, COVID and RSV, and Russo and Omenka say vaccinations could be crucial.

Vaccination is key to avoiding infection, minimizing illness
"It is important for people to realize that these vaccines are critical for preventing infection," Russo said.

He said the vaccines are imperfect and some people will get infected anyway, but that even then the vaccine can lessen the severity of the disease. Vaccines also help keep people from spreading the disease. He described vaccines as "probably the greatest medical invention in terms of saving lives and minimizing years of life lost." A huge body of research shows the rewards outweigh the risk, which is "very low but not zero," he said.

"You hear 'My neighbor got the vaccine and got sick,'" Russo said. "Yes, but they probably had a much less serious case."

RSV can be confused with other viruses
RSV, respiratory syncytial virus, usually peaks in December and January while infecting the nose, throat and lungs, usually causing mild, cold-like symptoms, the CDC says. Those symptoms make it difficult to distinguish it from the common cold, COVID-19, or influenza.

"And there's a ton of flu around right now," Russo said.

Almost every child is infected in the first five years of life − and it is the most dangerous in the first year of life. It also can be dangerous for the elderly and those who are immunocompromised.

Parents are 'low-hanging fruit' for norovirus spread
Norovirus causes inflammation of the stomach and intestines and is known as stomach flu. It is highly contagious, can survive and thrive on surfaces and can't be killed with most disinfectant sprays, he said. Russo suggested cleaning surfaces with diluted bleach and washing clothes in hot water to curb contamination.

"Imagine a household with young children where one of the children gets norovirus at day care or school," Russo said. "Mom and dad are taking care of the child − and become low-hanging fruit for infection. It can rip through households."

Cruise ships and other places where people are in close quarters can lead to an outbreak, he said.

"Dehydration can be a serious problem, and there can be 24-48 hours of fever, vomiting, diarrhea and generally short-term, total misery," he said. He suggested drinks with electrolytes as opposed to simply water while trying to weather the norovirus storm.

Many people are feeling lousy right now as the winter stew of respiratory viruses simmers. But there are a couple of unusual trends driving all the coughing, sneezing and fevers this year.

First, the good news: This winter's COVID-19 surge has been mild.

The current winter wave that we're kind of coming out right now does appear to be more mild than previous winters," says Dr. Heidi Moline, a medical officer at the Centers for Disease Control and Prevention.

In fact, the COVID surge appears to be the mildest since the pandemic began.

"This is the smallest winter wave we've had since the pandemic began," says Caitlin Rivers, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health.

The weekly rate at which people are getting hospitalized for COVID this winter peaked at about 4 per 100,000, compared with about 8 per 100,000 last season, about 11 per 100,000 in the 2022-2023 season and 35 per 100,000 in the 2021-2022 season, according to data from the CDC.

One possible explanation for the relatively mild COVID winter is that the U.S. experienced an unusually intense summer COVID wave that also started relatively late. As a result, many people may still have some immunity from when they had COVID during the summer.

"There are less people available to get infected because they had a recent boost in immunity," says Rivers.

At the same time, no new variant has evolved that's any better at getting around the immunity people have built up.

"The variants have been pretty similar," Moline says. "We haven't seen big viral changes."

Flu may be crowding out COVID
Another possible factor is "viral interference," says Aubree Gordon, an epidemiologist at the University of Michigan School of Public Health . That's a phenomenon that occurs when the presence of one virus pushes out other viruses. Some scientists think that may be one of the reasons there a decrease in infections with other respiratory viruses, such as flu and RSV, during the early, heavy COVID waves.

"It's possible that viral interference is playing a role this year," Gordon says. "There's a lot of influenza circulating. It may generate some non-specific immunity — some nonspecific protection, which then prevents people from getting other respiratory infections, such as SARS-CoV-2 — sort of crowds it out."

That said, COVID is still spreading widely, causing people to miss work, children to miss school and even making some people so sick they end up in the hospital or die.

Flu rebounds and could stick around
The bad news trend this year is the flu. This year's flu season started unusually early and has been spreading at high levels around the country. And now, it looks like the U.S. is experiencing a second peak of flu activity this winter.

"Influenza activity first peaked around the turn of the new year — late December, early January. Activity then declined for several weeks in a row, which is usually a sign that the season is on its way out," Rivers says. "But then it really took an unusual turn and started to rise again. So activity is now at a second peak — just as high as it was at the turn of the new year. It's unusual."

The rate at which people were going to doctor for a fever and cough or sore throat, which is one way the CDC tracks the flu, dropped from 6.8% to 5.4%, but then started to rise again, reaching 7 %, according to Rivers.

So the intensity of this year's flu season could have a long tail, she says. "This could turn out to be an unusually severe flu season," Rivers says.

The cause of the second peak remains unclear. So far testing hasn't spotted any signs that the H5N1 flu virus, which has been spreading among poultry and dairy cows, is circulating widely in people, contributing to the second peak.

So the cause remains a mystery, Rivers says. It could just be the kind of natural variation that happens with the flu.