Image of a person self-administering an at-home COVID-19 test.

COVID cases are rising again. Here’s a refresher on everything you forgot.

Can you use an expired test? How long do you need to isolate? With more infectious variants, here’s a reminder on how to protect yourself—and what to do if you get sick.

A resident processes a self-administered at-home COVID-19 test. Anyone who has respiratory symptoms and gets a negative home test should follow guidance from the CDC and take another test two days later.
Photograph by John Tully, Bloomberg/Getty Images

A new posse of infectious Omicron variants are causing more people to come down with COVID-19, and some are getting extremely sick. In the last week of August more than 650 people died from the disease—up 10 percent from the prior week—and 17,000 new patients were hospitalized.

With updated vaccines recently approved by the U.S. Food and Drug Administration, the U.S. Centers for Disease Control and Prevention recommended the shots for all Americans older than six months. Experts hope the immunity most Americans gained from prior bouts of COVID, past shots, and/or the vaccine that will be available within days, will make surges like one in early 2021—when some 20,000 people died each week due to COVID-related complications—less likely.

It’s unclear whether this late summer bump might indicate an annual pattern, since COVID-19 is too new to have seasons like the flu does, says Rick Martinello, an infectious disease expert at the Yale School of Medicine in New Haven, Connecticut. One factor contributing to the recent uptick in cases are the heat waves that baked much of the country last month, forcing people indoors where viruses spread more easily.

“Whether we’ll see cases rise a bit and plateau soon or instead have a significant peak is something we just don’t know right now,” Martinello says.

With the number of cases on the upswing, here are some reminders and recommendations about how to protect yourself and what to do if you think you have the virus or get sick.

Have your old COVID antigen tests expired? 

The COVID antigen tests you bought in the pharmacy or received free from the federal government are stamped with an expiration date, after which you are supposed to discard them. Many manufacturers received approval to extend their expiration dates after the tests were distributed.

But those past the extended expiry dates may still perform sufficiently, says Zishan Siddiqui, an assistant professor of medicine at the Johns Hopkins School of Medicine in Baltimore. He and his colleagues placed small viral samples on two groups of Abbott’s BinaxNow tests—some within the extended expiration date and others five months past—and found both performed similarly. (One difference: the positive line on expired tests was often fainter, indicating that older tests should be evaluated in bright light.)

“I think it’s reasonable for people to use an expired test they have at home,” Siddiqui says, especially if the alternative is not testing at all. Still, older kits, especially those stored in hot locations or crammed together, may have damaged swabs or test cards or degradation of important testing chemicals.

Anyone who has respiratory symptoms and gets a negative home test (whether expired or not) should follow guidance from the CDC and take another test two days later.

Swab the throat or the nose?

It turns out nasal samples concentrate more of the virus and are therefore more likely to yield a positive diagnosis. Plus, antigen tests were not designed for oral samples that could contain bacteria or other contaminants, Siddiqui says.

Can you get sick within days of SARS-CoV-2 exposure?

A recent study in France confirmed what people are feeling, that those exposed to Omicron develop symptoms earlier than they did after exposure to the original SARS-CoV-2 strain.

It’s possible that the incubation period is shorter due to the mutations. But it’s also likely these changes reflect improved understanding of when the virus is contagious, Martinello suggests.

Even today people vary greatly in how quickly they get sick. “I don’t think we yet fully understand what the incubation period for COVID is,” Martinello says.

How long should you isolate if testing positive for COVID?

Whether a person has a positive test or is likely to have the disease based on symptoms and exposure, it’s crucial they go home and immediately isolate from everyone, including people with whom they live.

This isolation should continue for a minimum of five days, which starts the day after the positive test or the appearance of symptoms, according to the CDC.

A sick person who shares a home should remain in a separate room and wear a mask during any brief forays to the bathroom or kitchen, Martinello says. (Fellow residents should wear a mask when they enter a shared space.) Weather permitting, they might open a window to disperse the virus. If they own a HEPA air filter it should be placed in the room near the head of the sick person’s bed, a location that captures more virus particles than outside the door or in other parts of the home.

The isolation period can end after five days if symptoms never developed, or after the person is improving and is free of fever (without drugs) at least 24 hours. Those with serious symptoms like shortness of breath or who have been hospitalized should isolate at least 10 days.

When is masking after isolation necessary? 

Once in public, the individual must wear a high-quality mask until 10 days have passed since symptoms began or testing positive. Remember: the first day is day zero. This is important because the sick person could be contagious for a full 10 days.

Researchers found that half of the National Basketball Association players repeatedly tested in 2021 still had high viral levels on day five. (If feasible, it is preferable to remain isolated at home longer than five days, Martinello says.)

However, it is safe to unmask before day 10 if two home antigen tests taken two days apart both yield negative results.

Who should take the antiviral drug Paxlovid? 

Those who are most likely to face hospitalization and death should talk with their healthcare provider about taking the antiviral medicine, Paxlovid, which continues to be effective against current strains. Vulnerable groups include people older than 50, those of any age who have not been vaccinated, and people 12 or older with serious medical conditions—chronic lung, liver, heart or kidney disease, cancer, diabetes—and those who are immunocompromised or have a weakened immune system (including from medications). 

This should be done early, as the medicine works only when started within five days after symptoms begin. Another option for people at high risk who can’t take Paxlovid is a three-day IV infusion of Remdesivir, which similarly blocks replication of the virus.

Some worry about getting a rebound case of COVID following Paxlovid, but it’s unclear whether the rebound is caused by the drug or by the disease. (Read more about why COVID rebounds aren’t definitively linked to Paxlovid.)

Should you get the new vaccine? 

The FDA and CDC recently approved new COVID vaccines for people six months and older. The benefits of vaccination outweigh side-effect risks for all these age groups, the CDC noted.

These mRNA shots from Moderna and Pfizer no longer target the original strain of SARS-CoV-2 but instead aim for the Omicron variant XBB.1.5 that more closely mirrors the strains currently circulating. Only a single dose is required, even for people who have not gotten prior vaccinations. (Children under five may require multiple doses.)

“Staying up to date on vaccines is the most effective tool in your toolkit,” says Vandana Madhavan, an infectious disease expert at Massachusetts General Hospital’s pediatric hospital in Boston.

In addition to preventing serious illness, vaccinations seem also to reduce the risk of developing long COVID following an infection.

How else can you protect yourself?

Avoiding crowds and masking remain extremely effective protection measures, but most people don’t need to do them 24/7. “Prevention is not an on-off switch but is more like a dimmer that you turn up or down depending on what is happening in the community or in your life,” Madhavan says.

People who have risk factors for severe disease or who live with people who do may need to keep the switch on brighter more of the time. But others might stay home more or wear face protection in crowded situations like public transportation, supermarkets, or the movies primarily when local caseloads are high or when they really want to avoid getting sick, perhaps because of an upcoming family wedding or vacation, she says.

Even when only one person wears a mask they are protected. Research by the CDC makes clear that someone who wears a high-quality mask like an N95 or KN95 is 83 percent less likely than non-maskers to contract circulating virus.

A person’s tolerance for risk also plays a role for how much and where they might mask, Martinello says. “It takes potentially a moment to be exposed to enough virus from a nearby person to make you sick,” he notes. Whether someone wants to avoid nearly all exposure or is comfortable taking on a little risk is an individual decision.

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