Nobody wants to give Covid to a loved one (or anyone). But determining just how long you’re contagious isn’t an exact science, as it can vary from person to person.

So you may have a hard time figuring out whether you’re putting others at risk. However, there are rules you can follow and things you can know to help protect those around you — and to ease other concerns about your infection, too.

Here, experts share guidelines for how long you might be able to spread Covid and when you’re most contagious, including with the viral strain that is currently dominant.

It’s not always clear how long a person is contagious because, like a lot of things with Covid, the exact timeline depends on many factors, said Dr Stuart Ray, a professor of medicine and infectious diseases at the Johns Hopkins University School of Medicine in Baltimore.

But, Ray said, the conventional wisdom is that you are contagious and must isolate for five full days after your symptoms begin — with your first day of symptoms counting as day zero.

But keep in mind that you aren’t in the clear after five days.

“It’s often said then that you should wear a mask after that to try and protect others because it’s hard to be certain how long you’re infectious,” Ray said.

“That period often lasts up to 10 days,” he added — and once again, your first day of symptoms counts as day zero.

Long story short, you are likely contagious for about 10 days after symptoms begin. You should isolate for the first five days and wear a mask on at least days six through 10.

The phase when you’re most contagious starts about 48 hours before you test positive and ends five days after your symptoms begin, according to Dr Neha Vyas, a family medicine doctor at Cleveland Clinic in Ohio. She called this the “period of maximal contagiousness.”

So, you’ll want to be extra careful at this stage — though it’s hard to know if you’re sick before you have symptoms, which makes those first 48 hours really tricky.

Meanwhile, the amount of time between infection and symptoms has got shorter and shorter as Covid mutates, which means omicron sub-variants like XBB — currently the dominant strain in the US — can spread faster.

If you’re exposed to someone who tests positive for Covid, you can test yourself even before you have symptoms. Or, if you recently attended a crowded indoor event, you can take a test a few days later. Beyond that, there isn’t really a way to know you’re infected before you start showing symptoms.

And in the later period of your illness, remember that you can still spread Covid, which is why it’s important to wear a mask until at least the 10-day mark.

Anyone whose symptoms persist past day 10 and who continues to test positive can likely pass the virus to others. If that’s you, keep wearing a mask and avoiding indoor spaces and events, Ray said.

“If you are immunocompromised or you had a really [severe] Covid infection … then you could be contagious still for 20 days” after symptoms begin, added Vyas.

Long periods of contagiousness like this are rare, she stressed. But if you fall into either of those two categories, talk to your doctor for further guidance.

It’s not uncommon for someone to test positive on a lab test for weeks after a COVID-19 infection, “but it would be very unusual for someone to test positive for weeks on an antigen test,” Ray said.

Antigen tests are the type that you may have picked up from the pharmacy or received from the government.

Ray added that a positive antigen test is correlated with a virus’s ability to grow and infect. So if you have a positive antigen test, you are likely contagious.

And that works the other way around, too.

“We generally say if your symptoms are completely resolved and you have a negative test, you’re unlikely to be infectious,” Ray said.

If you’re past the 10-day mark and no longer symptomatic, but you’re feeling anxious about potentially spreading the virus to a loved one, there are things you can do.

“You can take two Covid tests 48 hours apart,” Vyas said. “If they’re both negative, you can [be] fairly certain that you’re not contagious anymore.”

She added that most people won’t need to do this as long as they follow the 10-day guidance. But if you’re nervous about passing on the virus, this is a good tactic.

“If possible, a contagious individual should use a separate bedroom and bathroom, especially during this five-day period [after symptoms begin],” said Dr Ali Khan, the chief medical officer at Oak Street Health.

When that isn’t possible, wear a well-fitting mask around other people in your home.

Khan added that an infected person should have their own tableware and sheets, and that they should avoid high-touch items.

“Don’t forget to wash your hands frequently,” Khan said — and this goes for people who are not infected, too.

Lastly, to protect both yourself and your loved ones, make sure you’re up to date on your Covid boosters.

“It’s definitely not too late to get Covid and flu shots, as they will still curb severe symptoms, even if you do contract illness,” Khan said.