It's winter, that cozy season that brings crackling fireplaces, indoor gatherings — and a wave of respiratory illness. Nearly four years since the pandemic emerged, people are growing weary of dealing with it, but the virus is not done with us.

Nationally, a sharp uptick in emergency room visits and hospitalizations for COVID-19, influenza, and respiratory syncytial virus, or RSV, began in mid-December and appears to be gaining momentum.

Here are a few things to know this time around:

What's circulating now?

The COVID virus is continually changing, and a recent version is rapidly climbing the charts. Even though it appeared only in September, the variant known as JN.1, a descendant of omicron, is rapidly spreading, representing between 39% to half of the cases, according to pre-holiday stats from the Centers for Disease Control and Prevention.

Lab data indicates that the updated vaccines, as well as existing COVID rapid tests and medical treatments, are effective with this latest iteration. More good news is that it "does not appear to pose additional risks to public health beyond that of other recent variants," according to the CDC. Even so, new COVID hospitalizations — 34,798 for the week that ended Dec. 30 — are trending upward, although rates are still substantially lower than last December's tally. It's early in the season, though. Levels of virus in wastewater — one indicator of how infections are spreading — are "very high," exceeding the levels seen this time last year.

And don't forget, other nasty bugs are going around. More than 20,000 people were hospitalized for influenza the week ending Dec. 30, and the CDC reports that RSV remains elevated in many areas.

"The numbers so far are definitely going in the not-so-good direction," said Ziyad Al-Aly, the chief of the research and development service at the Veterans Affairs St. Louis Healthcare System and a clinical epidemiologist at Washington University in St. Louis. "We're likely to see a big uptick in January now that everyone is back home from the holidays."

But no big deal, right? 

Certainly, compared with the first COVID winter, things are better now. Far fewer people are dying or becoming seriously ill, with vaccines and prior infections providing some immunity and reducing severity of illness. Even compared with last winter, when omicron was surging, the situation is better. New hospitalizations, for example, are about one-third of what they were around the 2022 holidays. Weekly deaths dropped slightly the last week of December to 839 and are also substantially below levels from a year ago.

"The ratio of mild disease to serious clearly has changed," said William Schaffner, a professor of medicine in the division of infectious diseases at Vanderbilt University School of Medicine in Nashville, Tennessee. 

Even so, the definition of "mild" is broad, basically referring to anything short of being sick enough to be hospitalized. 

While some patients may have no more than the sniffles, others experiencing "mild" COVID can be "miserable for three to five days," Schaffner said.

How will this affect my day-to-day life?

"Am I going to be really sick? Do I have to mask up again?" It is important to know the basics.

For starters, symptoms of the COVID variants currently circulating will likely be familiar — such as a runny nose, sore throat, cough, fatigue, fever, and muscle aches.

So if you feel ill, stay home, said Marcus Plescia, chief medical officer of the Association of State and Territorial Health Officials. "It can make a big difference."

Dust off those at-home COVID test kits, check the extended expiration dates on the FDA website, and throw away the ones that have aged out. Tests can be bought at most pharmacies and, if you haven't ordered yours yet, free test kits are still available through a federal program at COVID.gov. 

• Do COVID-19 tests still work after they expire? Here's how to tell.
• More free COVID-19 tests can be ordered now, as uptick looms

Test more than once, especially if your symptoms are mild. The at-home rapid tests may not detect COVID infection in the first couple of days, according to the FDA, which recommends using "multiple tests over a certain time period, such as two to three days."

With all three viruses, those most at risk include the very young, older adults, pregnant people, and those with compromised immune systems or underlying diseases, including cancer or heart problems. But those without high-risk factors can also be adversely affected.

While mask-wearing has dropped in most places, you may start to see more people wearing them in public spaces, including stores, public transit, or entertainment venues.

Although a federal mask mandate is unlikely, health officials and hospitals in at least four states — California, Illinois, Massachusetts, and New York — have again told staff and patients to don masks. Such requirements were loosened last year when the public health emergency officially ended. 

Such policies are advanced through county-level directives. The CDC data indicates that, nationally, about 46.7% of counties are seeing moderate to high hospital admission rates of COVID. 

"We are not going to see widespread mask mandates as our population will not find that acceptable," Schaffner noted. "That said, on an individual basis, mask-wearing is a very intelligent and reasonable thing to do as an additional layer of protection."

The N95, KN95, and KF94 masks are the most protective. Cloth and paper are not as effective.

And, finally, if you haven't yet been vaccinated with an updated COVID vaccine or gotten a flu shot, it's not too late. There are also new vaccines and monoclonal antibodies to protect against RSV recommended for certain populations, which include older adults, pregnant people, and young children.

Generally, flu peaks in midwinter and runs into spring. COVID, while not technically seasonal, has higher rates in winter as people crowd together indoors. 

"If you haven't received vaccines," Schaffner said, "we urge you to get them and don't linger." 

Aren't we all going to get it? What about repeat infections?

People who have dodged COVID entirely are in the minority. 

At the same time, repeat infections are common. Fifteen percent of respondents to a recent Yahoo News/YouGov poll said they'd had COVID two or three times. A Canadian survey released in December found 1 in 5 residents said they had gotten COVID more than once as of last June. 

Aside from the drag of being sick and missing work or school for days, debate continues over whether repeat infections pose smaller or larger risks of serious health effects. There are no definitive answers, although experts continue to study the issue.

Two research efforts suggest repeat infections may increase a person's chances of developing serious illness or even long COVID — which is defined various ways but generally means having one or more effects lingering for a month or more following infection. The precise percentage of cases — and underlying factors — of long COVID and why people get it are among the many unanswered questions about the condition. However, there is a growing consensus among researchers that vaccination is protective. 

Still, the VA's Al-Aly said a study he co-authored that was published in November 2022 found that getting COVID more than once raises an "additional risk of problems in the acute phase, be it hospitalization or even dying," and makes a person two times as likely to experience long COVID symptoms. 

The Canadian survey also found a higher risk of long COVID among those who self-reported two or more infections. Both studies have their limitations: Most of the 6 million in the VA database were male and older, and the data studied came from the first two years of the pandemic, so some of it reflected illnesses from before vaccines became available. The Canadian survey, although more recent, relied on self-reporting of infections and conditions, which may not be accurate.

Still, Al-Aly and other experts say taking preventive steps, such as getting vaccinated and wearing a mask in higher-risk situations, can hedge your bets.

"Even if in a prior infection you dodged the bullet of long COVID," Al-Aly said, "it doesn't' mean you will dodge the bullet every single time."

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KFF Health News, formerly known as Kaiser Health News (KHN), is a national newsroom that produces in-depth journalism about health issues and is one of the core operating programs at KFF — the independent source for health policy research, polling, and journalism.

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