Has a ‘quademic’ hit the US? 4 viral infections and what to know about them

Four viruses are circulating in the U.S., sparking concerns of a possible "quademic."

Influenza, COVID-19, RSV and norovirus are all at "very high levels" around the country, according to Samuel Scarpino, director of AI and life sciences and professor of health sciences at Northeastern University in Boston.

"We are in the middle of a very serious situation with respect to circulating pathogens," he told Fox News Digital.

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"Based on data from our national wastewater surveillance system, some parts of the country, such as Boston, seem to be entering the peak for all four diseases, but in other areas, cases are still rising," Scarpino added.

Dr. Marc Siegel, clinical professor of medicine at NYU Langone Health and Fox News senior medical analyst, noted that it is currently peak respiratory virus season.

"It is not a ‘quad-demic,’ per se, just a lot of respiratory viruses and bacteria at once," he said to Fox News Digital.

On top of the four viruses, Siegel warned of some bacterial outbreaks that can cause respiratory illness, such as mycoplasma, pertussis and strep.

The Centers for Disease Control and Prevention (CDC) reported an 18.8% positivity rate for flu tests for the week ending Jan. 11, stating that "seasonal influenza activity remains elevated across most of the country."

There were also 11 pediatric deaths related to influenza, bringing the total to 27 deaths this season, the agency stated.

COVID-19 was at a 6.6% test positivity as of Jan. 11, with 1.3% of emergency room visits resulting in a diagnosis and 1.8% of all deaths linked to the virus, per CDC data.

RSV (respiratory syncytial virus, which is a highly contagious virus that infects the lungs, nose and throat) has a test positivity of 8.9%.

Cases of norovirus, more commonly known as the stomach bug, are also surging. 

Between August 1 and Dec. 11, 2024, there were 495 norovirus outbreaks reported in the U.S., compared to 363 in the same time period last year, according to the CDC.

Kenneth Perry, MD, an emergency physician in South Carolina, said his hospital has recently seen an uptick in emergency department visits tied to these infections.

"From cough to nasal congestion and even fever, it is difficult to differentiate between the discrete viruses," he told Fox News Digital. "For most people, knowing which virus they have is purely an academic discussion. For some patients, however, the specific virus is very important."

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The possibility of someone having all four viruses at once is very low, Perry said — "but it’s not completely out of the realm of possibility for people to have two or even three at the same time."

Siegel agreed that with multiple viruses circulating, it can be a challenge for practicing internists and infectious disease specialists to tell the difference.

"Respiratory panels at hospitals, urgent care centers and labs can be helpful to distinguish between them," he said.

There are combined rapid tests available that simultaneously screen for two types of influenza and COVID, Scarpino pointed out. 

"Of the four viruses in widespread circulation, all post a unique risk of severe illness in the elderly," Dr. Jacob Glanville, CEO of Centivax, a San Francisco biotechnology company, told Fox News Digital.

RSV poses unique risks for infants, experts agree.

"For young infants, breathing through their nose is imperative in order to eat, and RSV can cause severe amounts of nasal congestion," Perry warned. This congestion can disrupt babies’ ability to consume enough calories, he added.

For norovirus, dehydration can become a "major problem," according to Perry. 

"Again, young infants who cannot have water or sports drinks to help maintain hydration can be most susceptible."

Long COVID is a "significant concern" for most adults, according to Glanville, "as the chronic disorder is yet to be fully understood and effective treatments have yet to be developed."

Scarpino noted that influenza has historically been a leading cause of death in the U.S.

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"Despite us being more used to worrying about COVID these days, it’s important to take the flu very seriously," he added.

People with underlying risk factors are at a higher risk of severe illness for all four viruses, Scarpino added.

To prevent these four circulating viruses, Glanville recommends getting vaccinated when available, avoiding contact with those who are infected, and following proper sanitation practices.

"The best thing you can do to keep from getting any of these viruses is to keep your hands clean," Perry advised. "Washing hands especially after touching public surfaces is going to be the best way to keep from getting any of these viruses."

There are vaccines currently available for COVID, flu and RSV, but not for norovirus — although there is an mRNA vaccine in development, Scarpino pointed out.

"Even in places where cases have started falling, we’re far from being out of the woods, so there’s still time to get vaccinated," he said.

For those who contract any of the viruses, Siegel recommends focusing on hydration, getting plenty of rest and carefully monitoring symptoms.

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People who are sick should stay home, avoid interacting directly with others and wear masks in close quarters, the doctor advised.

Perry pointed out that flu and COVID are "cyclical" in their level of severity. 

"There are years when the flu virus is very mild, and others when it is more virulent," he told Fox News Digital. "The same goes for COVID, as we saw with the different variants that were present throughout the pandemic."

With the onset of these common seasonal viruses, Perry said it’s important for patients to have a "great relationship" with a primary care physician. 

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"This way, their risk category is well-known to their doctor and they can easily get the correct care for their health, even if they get one of these viruses."