How long before someone with COVID-19 is not contagious?

  • Experts say the highest infectivity window appears to occur 2 days before symptom onset to 3 days after symptom onset.
  • Rapid antigen tests can detect high viral loads and are currently considered reliable for telling people whether or not they might still be contagious.
  • Health officials recommend self-isolating for 5-10 days if you develop COVID-19.

Infectious disease specialists estimate that, on average, the vast majority of people who contract the coronavirus are most contagious immediately before and immediately after symptoms appear.

To research shows that most people will no longer be contagious 5-6 days after symptoms appear. Yet, some evidence suggests that a third of people who become infected stay contagious longer.

Health experts do not recommend using a PCR test to determine if you are still infectious, as these types of tests are sensitive and can detect small amounts of non-infectious virus.

Rapid antigen tests, on the other hand, can detect high viral loads and are currently considered more reliable in telling people whether or not they might still be contagious.

“For symptomatic infection, time since illness onset has been shown to be more reliable than the PCR test in predicting the presence of live virus. [or] contagious virus COVID-19”, Dr Charles Bailey, the medical director of infection control at Providence Mission Hospital and Providence St. Joseph Hospital in Orange County, Calif., told Healthline.

“Antigen testing may be better able to determine infectivity since its detection threshold for COVID-19 aligns more closely with an amount of virus capable of transmission,” he added.

According to Bailey, the duration of infectiousness varies from person to person and depends on the severity of the infection, the intensity of exposure and each person’s immune system.

In general, the highest infectivity window appears to occur 2 days before symptom onset to 3 days after symptom onset.

Contact tracing studies from the start of the pandemic found that it is less common for transmission to occur when exposed to a person 6 days after the onset of their symptoms.

It’s still possible to pass the virus on to others after 5 days of symptoms, so health officials advise people who have recently recovered from their illness to continue wearing a mask for 5 days when they are in the presence of other people.

One to study recently published in the International Journal of Infectious Diseases found that approximately one-third of infected people continue to be infectious after 5 days.

But it is unknown if this remains true with the Omicron variant.

A recent study from Japan found that patients infected with the Omicron variant shed the virus longer after the onset of symptoms.

The study suggests that peak viral shedding with the Omicron variant may be 2 or 3 days longer than previous variants.

Dr. Julie Parsonnet, an infectious disease epidemiologist at Stanford Medicine, says there doesn’t appear to be a strong relationship between a person’s symptoms and the amount of virus in their nose and throat.

But in general, people who test positive and are symptomatic are at higher risk of transmission and should self-isolate at home to avoid spreading the virus to others.

“People whose symptoms don’t improve — especially if they’re coughing and sneezing — should continue to stay home until they feel better,” Parsonnet said.

If someone with the virus coughs or sneezes, there is a greater chance that they can transmit the virus to others because they release respiratory droplets that carry the virus.

Researchers are still studying if and how symptoms correlate with a person’s contagion.

“We don’t know exactly how the duration of symptoms relates to how long someone is contagious, but we generally associate symptoms like fever as an indication that someone is still contagious,” said Dr. John Carlo, CEO of Prism Health North Texas and a member of the Texas Medical Association’s COVID-19 Task Force.

To research also showed that people with asymptomatic infections, although less likely than symptomatic people to spread the infection, can spread it to others.

Parsonnet says it’s difficult to quantify how long asymptomatic individuals are contagious because it’s difficult to identify when and how long they were infected.

“Asymptomatic transmission might be more common with the Omicron variant given its higher infectivity, but it’s too early to draw that conclusion now,” Bailey said.

There’s no reliable or easy way to tell if you’re still contagious, so health officials recommend isolating yourself at home for 5 to 10 days, depending on your symptoms.

Those who are asymptomatic or improving after 5 days are now advised that they can end their isolation but continue to wear a mask around other people for another 5 days.

According to the guidelines of Centers for Disease Control and Prevention (CDC), those who do not improve after 5 days should continue to self-isolate until their symptoms improve and the fever subsides.

Most infectious disease doctors do not recommend taking a PCR test to determine if you are still shedding the virus.

PCR tests are sensitive and can detect non-infectious virus after infection for up to 90 days.

Many doctors recommend using rapid antigen tests because they detect a high viral load, which may or may not correlate with how infected a person is.

“It’s important to remember that the currently available COVID-19 tests aren’t really designed to tell if someone is contagious or not. They are designed to test whether or not someone has a COVID-19 infection, which is slightly different,” Carlo said.

Infectious disease specialists estimate that, on average, the vast majority of people who contract the coronavirus are most contagious immediately before and immediately after symptoms appear.

But how long people are contagious varies from person to person, depending on the severity of their infection, the intensity of their exposure and the response of their immune system.

Recent data suggests that a third of people infected with COVID-19 are infectious for more than 5 days. There’s no perfect way to measure how long a given person has been infectious, but rapid tests – which detect high viral loads – can help people determine if they may still be infectious.

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