The latest variant of COVID-19 is so contagious that even people who have thus far avoided it are becoming infected, and 80 percent of Americans who have already become infected will likely catch it again, experts say.
Essentially, everyone in the country is at risk of infection now, even if they’re very careful, up to date on vaccines, or have already taken it, said Paula Cannon, a virologist at the University of Southern California.
“It’s crazy contagious,” said Cannon, who is recovering from his first case of COVID-19, caught while on vacation during the holidays in his native Britain.
“All the stuff that’s been protecting you for the past couple of years, I don’t think is going to protect you from this new crop of variants,” she said.
The number of serious infections and deaths remains relatively low, despite the high level of infections, he said, thanks to vaccinations and possibly previous infections. But the lack of universal masking means that people like her, who mask up, are also vulnerable.
The latest variant, called XBB.1.5, grew exponentially during the month of December, from about 1 percent of cases nationwide to 40 percent as of December 31, according to data from the Centers for Disease Control and Prevention. The variant probably underlies the vast majority of cases in New York and New England.
Its growth is likely due to characteristics of XBB.1.5 – it appears to bind even more closely to receptors in the human body than its predecessors – as well as human behavior, such as traveling and not disguising.
It’s a good idea to do what you can to avoid getting infected, said Dr. Ziyad Al-Aly, chief of research and development at the VA St. Louis Health Care System and a clinical epidemiologist at Washington University in St. Louis.
It’s still early days and there are many unknowns about XBB.1.5, he said. Every infection leaves someone vulnerable to a bad course of the disease and the lingering, miserable symptoms of long-lasting COVID, Al-Aly’s research shows.
“Reinfection makes you more at risk,” he said.
As the US enters its fourth year of COVID-19, we provide an update on the state of the pandemic. Here’s a preview of what you’ll learn in this article:
What to know about XBB.1.5 symptoms and how long they last
Symptoms of COVID-19 typically last five to seven days and can include fever, sore throat, body aches, fatigue, nausea, cough and sinus congestion, among other problems.
Symptoms with XBB.1.5 are the same as with previous variants and can range from almost nothing to shortness of breath and low oxygen levels requiring emergency medical attention.
Early in the pandemic, COVID-19 often costs people their sense of taste and smell, at least temporarily, but that symptom seems less common, perhaps due to vaccination or a previous infection rather than a change in the virus. said Dr. Peter Hotez, an infectious disease specialist and co-director of the Center for Vaccine Development at Texas Children’s Hospital.
How long does COVID last? How long have you been contagious?
It takes anywhere from two to 14 days for exposure to lead to symptoms and a positive test.
People with COVID-19 are contagious as long as they stay positive in a rapid test, typically for about 10 days but often longer.
The CDC recommends that people self-isolate for at least five days and wear an N95 protective mask or similar for at least 10 days when out and about. Day 1 is considered the first full day after the onset of symptoms.
A PCR test, which is considered the gold standard for diagnosing COVID-19, can stay positive for months because it detects both viral fragments and the entire infectious virus. To confirm the end of the contagious period, experts recommend a negative rapid test instead after 10 days or two within 48 hours if sooner.
Can you get COVID more than once?
Yes. While a previous infection provides some protection, this wears off over time and as the virus evolves into different variants.
Some people who have had a mild case with a first infection are hit harder the second or third time, while others may suffer less.
“Even if you’ve had it before, that doesn’t mean your next fight will be the same,” Cannon said. There are many factors at play in determining how severe an infection is, she said, including prior immunity, the nature of the variant and how long it has been since the last infection or vaccination.
It’s possible that her recent infection was much milder than her husband’s, for example, because she caught a cold a few days earlier, while her husband didn’t. A respiratory virus can put the immune system on high alert and may have provided some protection when exposed to COVID-19.
“It’s part of the larger dance between our bodies and our immune systems,” Cannon said.
How to avoid infection
The methods of avoiding infection haven’t changed, although they can be difficult to follow when no one else is: getting vaccinated, wearing a mask, and avoiding crowded spaces.
The first is to get vaccinated. This will protect against serious infections and reduce the risk of passing the virus to others, said Hotez, also dean of the National School of Tropical Medicine at Baylor College of Medicine.
The newer boosters, targeting both the original virus and the BA.4/BA.5 variants common this summer, are more protective against XBB.1.5 than older boosters. People who are up to date on their COVID-19 vaccines probably don’t shed as much virus for that long, so they’re also less likely to pass it on, he added.
Past infection provides some protection against serious illness, but that protection is “highly unreliable,” Hotez said.
The second is wearing a mask. Good-quality, well-fitting masks, such as N95 or KN95, can reduce the risk of infection.

Cannon said people sometimes get annoyed when he wears the mask “because it’s like I’m reminding them that (COVID) is still an issue.” But he doesn’t want to accidentally pass COVID on to someone who might be more vulnerable to the virus.
The third is to avoid crowded indoor spaces. You’re less likely to get infected in large indoor spaces with high ceilings and lots of ventilation than in cramped, airless ones.
What to do if you get sick
It’s a good idea to have a plan ready in case you get sick, Cannon said. He suggests that each plan includes:
- How to isolate yourself from others in your family
- The contact number of a healthcare professional who can prescribe an antiviral
- Equipment such as coronavirus rapid tests, additional masks, a thermometer and a pulse oximeter to make sure the patient’s blood oxygen level does not drop below 90 degrees
Every US household is eligible for four free coronavirus tests from the government which can be ordered from this link: covid.gov/tests.
For those over 60 years old or with medical conditions like obesity that increase the risk of serious illness, the first step after a positive test should be a call to the doctor to get the antiviral Paxlovid, she and others said. The government has pre-purchased millions of doses, so they are freely available.

Some doctors are reluctant to provide the antiviral because people may need to stop taking common medications during the five-day course of treatment, but it’s essential for people at high risk for serious illness, Hotez said. “Any senior who goes on Paxlovid isn’t dying,” she said.
“We can’t stop people from getting infected,” Cannon added, “but we can absolutely stop people from getting really sick. Gosh, why wouldn’t you take it?”
Because it’s better not to get infected
Each COVID-19 infection increases the risk of serious illness and long-term COVID, which sometimes leads to debilitating symptoms that can persist for a year or more.

Older adults are more vulnerable, Al-Aly said, “but that doesn’t mean young people are totally protected.” Long-term COVID can also affect people of any age, from infancy to the 101-year-old recently treated in his hospital, she said.
Vaccination reduces the risk of long-term COVID by 15% to 30%, according to a study it recently published. Another study she is working on shows that Paxlovid reduces the risk by 26%.
Cannon’s daughter works at a long-running COVID clinic and regularly sees patients in their 20s and 30s, “healthy people who haven’t even had a particularly bad bout of COVID who now have an extremely debilitating array of symptoms.”
All six experts USA TODAY interviewed this week rejected the notion that there is any benefit to getting infected: Vaccination provides better protection against future infections without the risk.
“I would be happy if I never had any viruses again,” Cannon said. “And I say this as a professional virologist.”
Could we be close to the end of COVID?
COVID-19 was perhaps the most successful virus in all of human history, Cannon said, infecting billions of people around the planet.
While he worries about how it might continue to evolve, he hopes it’s a good sign that within the last year all variants are descendants of omicrons.
Before that, the original, alpha, beta and delta virus had been “radically” different from each other.
“The virus is now in this committed lineage,” Cannon said, which could mean it won’t evolve from the protection against serious disease it almost everyone now has from vaccinations and previous infections.
Contact Karen Weintraub at [email protected]
Coverage of patient health and safety at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial contributions.