As you dive into your New Year’s resolutions, taking precautions to protect yourself from a quartet of infectious diseases can lessen your odds of starting off 2025 sick.
Flu, COVID, respiratory syncytial virus (RSV), and norovirus are making their winter rounds nationwide, and you may have heard the term “quad-demic” pop up online or in conversation (the first three are sometimes called a “triple-demic”). While the unofficial term for the four maladies circulating in tandem evokes a sense of impending doom, the quadruple threat isn’t so different from respiratory virus seasons past.
“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 tells Fortune. “I don’t want to panic people, but I would say if you haven’t been vaccinated and you’re eligible for vaccination—that means everybody 6 months of age and older—get that COVID shot, get that flu shot.”
An RSV vaccine is also available for adults 75 and older, adults 60 to 74 with certain chronic medical conditions, and expectant parents late in pregnancy, Hopkins stresses. “We have tools, we just have to use them.”
Dr. William Schaffner, a professor in the division of infectious diseases at Vanderbilt University Medical Center, refers to this time of year as respiratory virus vaccination season. Getting up to date on your immunizations is the best present you can give yourself and your loved ones, he says.
“Benjamin Franklin had it right: ‘An ounce of prevention is worth a pound of cure,’” Schaffner tells Fortune. “Let’s do what we can to prevent serious illness this year. We’re under-vaccinating.”
But how can we protect against norovirus, also known as “winter vomiting disease,” for which there’s no vaccine? Here’s where hand hygiene reigns supreme.
“Make ample use of soap and water,” Schaffner says, noting that alcohol-based hand sanitizer alone doesn’t defeat norovirus. “It’s highly contagious and you can probably pick it up on the environment, on your fingers, and then when you touch your nose and mouth, that’s how the transmission occurs.”
The same public health measures you likely adopted during the early days of COVID can help stave off illness, too, Hopkins stresses.
“It’s important to cover your coughs, ideally with your sleeve or with a handkerchief, not your hands,” Hopkins says. “Stay away from people who are sick, stay home when you’re ill, contact your health care professional about whether you need to get tested and about symptomatic measures.
“It’s important to stay active, particularly outdoor activities. Stay healthy as far as your eating and your fluid intake. And depending on what your health status is, you may really want to be careful about being in crowds, because that’s a natural breeding ground for those viruses to spread from person to person.”
Flu activity elevated in most U.S. states
The Department of Health and Human Services (HHS), of which the Centers for Disease Control and Prevention (CDC) is a part, often breaks the country up into 10 regions when mapping illnesses. The week ended Dec. 28, activity of influenza-like illness was elevated in all 10.
“Flu definitely has been picking up over the last six weeks and continues to increase week by week in terms of hospitalizations of flu,” Schaffner said Dec. 17, “not only in my neck of the woods, but around the country.”
Nationwide, the A (H3) strain of influenza accounted for the plurality of infections the three weeks ended Dec. 28, CDC records show.
A “very disappointing” segment of the population has been vaccinated against the flu this season, Hopkins says. According to the CDC, 42.7% of adults and 41.9% of children had been immunized as of the week ended Dec. 28. At that time last year, 43% of adults and 45.1% of children had been protected. If you missed the unofficial “vaccine before Halloween” deadline to get your flu shot, worry not, Hopkins says.
“It’s not too late,” Hopkins says. “It is not a bad time when we’ve got risk in front of us. And I would certainly prefer that people were vaccinated earlier, but I’m not going to make perfection the enemy of the good.”
Most adults haven’t gotten updated COVID vaccine
It’s hard to believe we’re approaching the five-year anniversary of SARS-CoV-2, the virus that causes COVID, worming its way into the U.S. Though COVID is now endemic, it remains a highly infectious disease whose long-term consequences are unfurling. Unvaccinated individuals have a higher risk of severe infection, hospitalization, and death, and thanks in part to lingering COVID fatigue, uptake of the new 2024–25 vaccine has been less than ideal.
Only one in five adults (21.5%) had gotten the updated jab as of the week ended Dec. 28, the CDC estimates. Still, uptake was slightly higher than that of the 2023–24 vaccine (18%) at the same time last year. Just 10.6% of children had been vaccinated, on par with last year’s 10.7%. The CDC recommends everyone 6 months and older get the vaccine targeting this season’s variants—even if they’ve had COVID or received an older version of the vaccine. If you have a compromised immune system, ask your doctor about your eligibility for extra booster doses.
The summer surge in COVID infections may be in the rearview mirror—case positivity peaked at 17.8% the week ended Aug. 10—but the national positivity rate has begun to creep back up in recent weeks. The rate was 7.1% the week ended Dec. 28, up from 4.1% six weeks earlier. Throughout the four weeks ended Dec. 28, test positivity was highest (6.8%) in regions 5 and 8, which includes Colorado, the Dakotas, Illinois, Indiana, Michigan, Minnesota, Montana, Ohio, Utah, Wisconsin, and Wyoming.
While rapid COVID tests are now widely available in stores and online, it’s not too late to order four free tests for your household at COVIDtests.gov.
Less than half of adults 75+ have received RSV jab
Unlike annual COVID and flu shots, the newer RSV vaccine—for now at least—is a one and done. The first FDA-approved RSV vaccine, Arexvy, manufactured by Fortune 500 Europe company GSK, didn’t become available until mid-2023 and uptake of the now three available vaccines has been slow.
“[RSV] can be very risky, but people are not as aware of it as a virus in itself,” Dr. Sujata Ambardar, an infectious disease specialist at Inova Fairfax Hospital in Falls Church, Va., previously told Fortune. “They think of COVID, flu, and other viruses.”
Less than half of adults 75 and older (43.6%) had been vaccinated as of the week ended Dec. 28, compared to a third (33.6%) of adults 60 to 74, CDC records show.
Test positivity was 12.8% the week ended Dec. 28, up from 10.4% at the same time last season. This rate was at least 11% across most of the country. Region 3—Delaware, the District of Columbia, Maryland, Pennsylvania, and the Virginias—had the highest test positivity (23.1%).
Norovirus spread in U.S. hasn’t reached level of U.K. outbreak
Norovirus infections have been largely increasing since early fall. Test positivity, as a three-week moving average, hit a season high (22.6%) the week ended Dec. 28, compared to 6% the week ended Sept. 7.
Norovirus is tracked in Census regions rather than HHS ones. The week ended Dec. 28, test positivity was highest (26.4%) in Region 4, which covers the West, from Colorado to California to Hawaii.
“There’s a large outbreak in the U.K. at the moment, in Britain, and they’re very concerned about it,” Schaffner told Fortune just before the holidays. “We’ve had scattered reports of norovirus but nothing huge…we anticipate that we’ll get more of norovirus but we haven’t had the comparable increase that they’ve had.”
Schaffner added, “Holiday travel has already started and will become intense. We’ll have many holiday parties, family reunions, and the like. These are optimal circumstances for all of these viruses, all four, to spread from person to person.”
For more on infectious diseases:
- Yes, you can get the COVID, flu, and RSV vaccines at once. Here are the pros and cons
- New COVID vaccines are here. What to know about latest shots in wake of nation’s biggest summer surge
- New flu shots have arrived. Here’s the best time to get your annual vaccine
- RSV can be deadly, especially for older adults. What to know about symptoms and the new vaccine
- Norovirus rates have skyrocketed by 340% this season. Here’s where the ‘winter vomiting disease’ is spreading and why
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