Staying healthy in the New Year presents a new challenge for Americans who are coping with what health officials are calling a “quad-demic,” which involves a quartet of infectious viruses that are making the rounds.
Each of the maladies can target different groups and age ranges, but here’s what you need to know to avoid contracting these illnesses and some tips for remaining healthy.
What is the quad-demic?
Although the trifecta of flu, COVID-19 and respiratory syncytial virus (RSV) are commonly paired, norovirus outbreaks around the U.S. have added to concerns of a quad-demic.
“All of the viruses are here, it’s just they’re affecting different areas a little bit differently,” Dr. Robert Hopkins Jr., medical director of the National Foundation for Infectious Diseases, told Fortune.
Flu
Cases of influenza, or the flu, reached 40 million between 2023-2024, according to the Centers for Disease Control and Prevention (CDC).
Most people recover from the flu within days to a couple of weeks, but some cases can become severe. Approximately 28,000 people died last flu season, per the CDC.
Flu symptoms include:
Fever or feeling feverish/chills
Cough
Sore throat
Runny or stuffy nose
Muscle or body aches
Headaches
Fatigue
COVID-19
COVID-19 has become a part of life just as the flu once did. Cases are nowhere near as high as they were when the virus was first introduced, but the U.S. is still seeing positive tests, hospitalizations and deaths.
COVID-19 antigen home tests indicating a positive result are photographed in New York. (AP Photo/Patrick Sison, File)
Between Oct. 1 and Dec. 14, the CDC estimates there were between 2.7 and nearly 5 million illnesses. Hospitalizations in major cities like Los Angeles, Chicago and New York were all up sharply as the year came to an end and as 2025 began.
COVID-19 symptoms include:
Fever or chills
Cough
Shortness of breath or difficulty breathing
Sore throat
Congestion or runny nose
New loss of taste or smell
Fatigue
Muscle or body aches
Headache
Nausea or vomiting
Diarrhea
COVID-19 and flu symptoms are similar, but they are caused by different viruses.
“You cannot tell the difference between flu and COVID-19 by symptoms alone because some of the symptoms are the same,” the CDC advises.
Anyone experiencing symptoms should take a COVID test, which can be found at testing sites, your doctor’s office or over-the-counter at pharmacies.
RSV
RSV, or respiratory syncytial virus, is a respiratory illness that affects the nose, throat and lungs, usually peaking in December and January.
The symptoms are similar to the common cold and other respiratory infections like the flu and COVID-19.
Infants and older adults are most susceptible. RSV can cause other illnesses like bronchiolitis, which is the inflammation of the lungs’ small airways, and pneumonia.
RSV symptoms include:
Runny nose
Congestion
Decrease in appetite
Coughing
Sneezing
Fever
Wheezing
The CDC warns not all symptoms will appear at once and may come in stages. Infants may experience only irritability, decreased activity and breathing difficulties without the other symptoms.
Norovirus
The stomach bug is striking again. Norovirus is highly contagious, spreads through contact and causes inflammation of the stomach and intestines.
This electron microscope image provided by the Centers for Disease Control and Prevention shows a cluster of norovirus virions. (Charles D. Humphrey/CDC via AP, File)
The CDC reports about 19 to 21 million annual cases.
People of all ages can get norovirus, but more severe infections occur in children younger than 5 years old, older adults and people with weakened immune systems.
Norovirus symptoms typically develop within 12-48 hours of exposure. They include:
Diarrhea
Vomiting
Nausea
Stomach pain
Fever
Headache
Body aches
Dehydration
What areas are affected?
The illnesses are hitting various pockets of the country, according to Dr. Dana Hawkinson, medical director for the Infection Control and Prevention program at the University of Kansas Medical Center.
Increases in flu cases have been the most problematic around the country, Hawkinson told NewsNation. New cases of COVID-19 are also being reported after the number of positive cases dropped following a spike over the summer months, he said.
How to prevent getting sick
Doctors are encouraging Americans who have not gotten a flu shot or the latest COVID-19 vaccine to avoid contracting one or more of the prevalent viruses. According to the CDC, 40.8 percent of adults have gotten the flu vaccine, while just 20 percent of Americans have been vaccinated for COVID-19.
A vaccine for RSV is also available for residents who are 75 years of age or older or those who live with certain health conditions. RSV vaccines are generally available to anyone 60 years of age or older, Hawkinson said. However, if residents got the RSV shot last year when the vaccine was first released, they do not need to get a second dose.
There is currently no vaccine for norovirus, but doctors say the best way to avoid this virus is to follow good hygiene practices, including regular handwashing.
Hawkinson told NewsNation it is not too late to get a flu shot. On average, 10 to 14 days are normally required to build up immunity to a virus after a vaccine has been administered. Flu shots that are administered now can still be effective, Hawkinson said.
Are masks making a comeback?
Masks became commonplace during the COVID-19 pandemic, and usage in places like hospitals, doctor’s offices and dental practices remained in place. Now, some of those requirements are making a comeback.
Amid threats of the quad-demic, hospitals such as Duke Health in North Carolina and Mass General Brigham in Massachusetts updated their masking and visitor guidelines, the Daily Mail reported. Hospitals in at least eight states — including Wisconsin, California, Illinois, Indiana, New Jersey and New York — are either requiring or strongly recommending masks in their facilities, the report said.
Exposure and hygiene are key in preventing all four illnesses, including hand-washing and staying home when ill.
While requirements and mandates in medical facilities are changing, masks in public places like restaurants, bars and gyms remain a personal preference.
NewsNation’s Ashley Soriano contributed reporting to this story
NewsNation is owned by Nexstar Media Group, which also owns The Hill.
