How long could it take for someone to test positive for COVID following an exposure to someone who had the virus?
It's a question many are asking following holiday gatherings amid surging omicron variant cases.
Testing demand continues to soar as the new year gets underway and some experts say the omicron variant has "sped up" timing for what many have come to know with COVID.
"With recent variants, we've seen decreases in what we call the incubation period -- the time between exposure and infection," Boston Medical Center's Dr. Cassandra Pierre said this week. "What we've seen with omicron compared to the previous incubation time -- which is seven days between time exposed to infected -- it's gotten down to three days, so it's a shorter period of time."
Get Boston local news, weather forecasts, lifestyle and entertainment stories to your inbox. Sign up for NBC Boston’s newsletters.
Changes sparked by the variant have resulted in new guidance from the Centers for Disease Control and Prevention, which shifted the timing for isolation and quarantine.
Here's what we know so far.
How long after COVID exposure could you test positive?
Local
In-depth news coverage of the Greater Boston Area.
According to the CDC, the incubation period for COVID is between two and 14 days, though the newest guidance from the agency suggests a quarantine of five days for those who are not boosted, but eligible or unvaccinated. Those looking to get tested after exposure should do so five days after the exposure or if they begin experiencing, the CDC recommends.
Those who are boosted and vaccinated, or those who are fully vaccinated and not yet eligible for a booster shot, do not need to quarantine, but should wear masks for 10 days and also get tested five days after the exposure, unless they are experiencing symptoms.
Still, for those who are vaccinated and boosted but are still looking to be cautious, medical experts say an additional test at seven days could help. But testing is likely not necessary after seven days following exposure for those who are vaccinated and boosted.
When is the Best Time to Get Tested After Exposure?
The CDC states that anyone who may have been exposed to someone with COVID should test five days after their exposure, or as soon as symptoms occur.
"If symptoms occur, individuals should immediately quarantine until a negative test confirms symptoms are not attributable to COVID-19," the guidance states.
Medical experts say that even though incubation times are changing, those who test early should continue testing even if they get negative results.
How Soon Might COVID Symptoms Appear?
According to earlier CDC guidance, COVID symptoms can appear anywhere from two to 14 days after someone is exposed to the virus.
Anyone exhibiting symptoms should get tested for COVID-19.
Some people may never experience symptoms, though they can still spread the virus.
A person is also considered contagious before symptoms appear.
When Are People with COVID Most Contagious?
The CDC says that its guidelines were updated to reflect growing evidence that suggests transmission of COVID-19 often occurs one to two days before the onset of symptoms and during the two to three days afterward.
For those without symptoms, CDC guidance states they are considered contagious at least two days before their positive test.
How Long Should you Quarantine or Isolate?
First things first, those who believe they have been in contact with someone who has COVID and are unvaccinated should quarantine. Those who test positive, regardless of vaccination status, must isolate, according to the Centers for Disease Control and Prevention.
Massachusetts General Hospital's Dr. Ali Raja said he talks to his patients all the time about the difference between isolation and quarantine.
"Quarantine sounds a lot scarier," he said. "It's actually when you have been exposed and either aren't fully vaccinated or you're not vaccinated at all. You stay home even if you don't have the virus. Isolation is when you've actually tested positive regardless of whether you had symptoms."
"For either one you stay away from people, stay home for five days, and ideally test negative before coming out of it," he added.
Here's more on the differences between the two:
Quarantine
Those who have been within six feet of someone with COVID for a cumulative total of at least 15 minutes over a 24-hour period should quarantine for five days if unvaccinated, or if they are more than six months out from their second vaccine dose, according to updated CDC guidance issued Monday.
Once that period ends, they should partake in strict mask use for an additional five days.
Previously, the CDC said people who were not fully vaccinated and who came in close contact with an infected person should stay home for at least 10 days.
Prior to Monday, people who were fully vaccinated — which the CDC has defined as having two doses of the Pfizer or Moderna vaccines, or one dose of the Johnson & Johnson vaccine — could be exempt from quarantine.
Those who are both fully vaccinated and boosted do not need to quarantine if they are a close contact of someone with COVID, but should wear a mask for at least 10 days after exposure. The same goes for those who are fully vaccinated and not yet eligible for their booster shot.
Isolation
People who are positive for COVID should stay home for five days, the CDC said Monday, changing guidance from the previously recommended 10 days.
At the end of the period, if you have no symptoms, you can return to normal activities but must wear a mask everywhere — even at home around others — for at least five more days.
If you still have symptoms after isolating for five days, stay home until you feel better and then start your five days of wearing a mask at all times.
So how do you calculate your isolation period?
According to the CDC, "Day 0 is your first day of symptoms." That means that Day 1 is the first full day after your symptoms developed.
For those who test positive for COVID but have no symptoms, Day 0 is the day of the positive test. Those who develop symptoms after testing positive must start their calculations over, however, with Day 0 then becoming the first day of symptoms.
When Should You Call a Doctor?
The CDC urges those who have or may have COVID-19 to watch for emergency warning signs and seek medical care immediately if they experience symptoms including:
- Trouble breathing
- Persistent pain or pressure in the chest
- New confusion
- Inability to wake or stay awake
- Pale, gray, or blue-colored skin, lips, or nail beds, depending on skin tone
"This list is not all possible symptoms," the CDC states. "Please call your medical provider for any other symptoms that are severe or concerning to you."
You can also notify the operator that you believe you or someone you are caring for has COVID.
What If You Test Positive Using an At-Home Test?
Those who test positive using an at-home test are asked to follow the latest CDC guidelines and communicate the results to their healthcare provider, who is responsible for reporting test results to the state health department.
Health experts say people should assume the test results are accurate and should isolate from others to reduce the risk of spreading the virus.
When Can You Be Around Other People After Having COVID?
If you had symptoms, the CDC says you can be around others after you isolate five days and stop exhibiting symptoms. However, you should continue to wear masks for the five days following the end of symptoms to minimize the risk to others.
