As always, it’s impossible to distinguish COVID from the flu, RSV, and other common winter illnesses like rhinoviruses, enteroviruses, and parainfluenza viruses by symptoms alone. Even with the new, highly mutated COVID variant “Pirola” JN.1, now globally dominant, this remains true. What’s more, it’s possible to have two or more infections at the same time.

As always, testing—at a health care facility or at home, in the case of COVID—is the only true way to determine the source of your illness. And while you should consult your health care provider, if your symptoms are mild and you don’t have other health conditions, the cause may not matter.

Still, with a new COVID variant making a splash, it’s fair to wonder if coronavirus symptoms have changed or if precautions like masking are again warranted. Here’s what you need to know to manage the winter illnesses that are likely headed your way.

Are JN.1 symptoms different from normal COVID symptoms?

The jury is still out. Cases of diarrhea, which may or may not be related, are reportedly on the rise. This comes as speculation swirls that the virus might be taking up residence in the gut—versus like the upper respiratory tract, where Omicron tends to hang out, or the lower respiratory tract, where initial strains of COVID wreaked havoc.

Keep an eye out for GI symptoms and realize they could be signs of COVID, not just the stomach flu, experts advise. But as Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security, points out, COVID has always caused GI symptoms in some, including nausea, vomiting, and diarrhea.

Otherwise, keep an eye out for the usual COVID symptoms, which may include:

• Fever
• Chills
• Cough
• Shortness of breath/difficulty breathing
• Fatigue
• Muscle/body aches
• Headache
• Sore throat
• Congestion/runny nose

Is JN.1 causing more severe cases of COVID?

Once again, the jury is still out. What we do know, however, is that COVID hospitalizations are trending upward in the U.S. and elsewhere, as are cases of JN.1.

In the U.S., COVID hospital admissions had risen 10% week-over-week as of Dec. 16, according to the latest federal health data. And JN.1 was projected to lead U.S. COVID cases, estimated to be behind 44% of them as of Dec. 22.

Globally, reported sequences of JN.1 increased eightfold in a three-week period during late November into early December, according to the World Health Organization’s Dec. 22 COVID update. Reported hospitalizations rose 23% globally during that period.

But correlation does not equal causation. It’s important to note that sequencing of COVID samples and reporting of various metrics like hospitalizations and deaths have declined greatly since the height of the pandemic, meaning statistics could appear misleading. For example: Hospitalizations may be rising quicker than we realize. Or perhaps JN.1 is responsible for a smaller share of sequences than we know.

It’s also important to note that while COVID hospitalizations are on the rise globally, JN.1 may not be to blame—not entirely, at least. Population immunity—or the collective resistance to a virus in a group of people due to vaccination and/or prior infection—wanes after three to six months, on average. With COVID vaccine and booster uptake at low levels—only 18% of U.S. adults have received the latest booster, released in September—the disease will spread more widely, and severe outcomes like hospitalizations and deaths could become more common, regardless of variant.

Do COVID tests still work against JN.1?

At-home COVID tests remain as accurate as they’ve ever been, experts say. But they caution that many infected people test too early or too late, when viral loads are low and unlikely to turn a test positive. If you have symptoms but test negative, wait another couple of days and test again, experts recommend.

What viruses are circulating in the U.S. this winter?

In short: the usual suspects. Around 12% of all tests for COVID, flu, and RSV performed in the U.S. were returning positive mid-December, according to the latest available data from the U.S. Centers for Disease Control and Prevention. For some perspective, a long-ago abandoned goal from the World Health Organization and other public health agencies was a test-positivity rate of below 5%, for communities that wanted to cast aside pandemic precautions.

Should I be masking this winter?

Experts are increasingly recommending it, and not just because of COVID. Some hospitals, like those in New York and Illinois, are again requiring masks because of high levels of respiratory pathogen circulation in their area. And Yolo County in Northern California is recommending masking in public spaces due to surging levels of COVID and RSV.

Dr. Stuart Ray, vice chair of medicine for data integrity and analytics at Johns Hopkins’ Department of Medicine, recommends “wearing an effective respirator in public spaces, especially indoors, when it doesn’t interfere with essential tasks.”

“Not a bad way to keep your face warm, too,” he adds.