- Evidence from more than 100 studies shows that the contagiousness of COVID-19 in people with the virus peaks around the onset of symptoms and declines rapidly within a week.
- A rapid antigen test may only return a positive result during an infectious period, which means a negative result after symptoms return may indicate that you are no longer infectious.
- Compared to other variants, Omicron has a shorter incubation period, between two and four days.
The U.S. Centers for Disease Control and Prevention (CDC) released new quarantine guidelines for people with COVID-19 in December, shortening the quarantine period from 10 days to five. The agency said research suggests transmission occurs early in the infection process.
Health professionals are divided on the guidance. Some worry that shortening the quarantine period could accelerate the rapid spread of the Omicron variant. The contagiousness of COVID-19 typically peaks the day before symptoms appear, according to studies cited by the CDC. Additionally, a negative antigen test may indicate that the infectious period has ended.
When do symptoms appear?
Compared to previous variants, Omicron reportedly has a shorter incubation period — about two to four days — meaning symptoms develop more quickly after exposure.
In a study of the Omicron outbreak in Oslo, Norway, following a Christmas party in November, researchers found that 45 percent of 80 confirmed or suspected cases developed symptoms three days after the party. In a study of a similar outbreak in South Korea, a slightly longer median incubation period was observed, at 4.2 days.
But symptom onset doesn’t always coincide with contagion. More than 20% of transmission can be attributed to asymptomatic or presymptomatic individuals (one to two days before symptoms appear).
When is the most contagious during a COVID-19 infection?
Citing a 2020 review of 113 studies in 17 countries, the CDC found evidence that COVID-19 viral loads peak at the onset of symptoms. The reviewers concluded that the entire infectious period ranged from 2 to 3 days before symptom onset to 8 days after symptom onset.
This means that people infected with COVID-19 are most contagious when they start showing symptoms, after which the likelihood of transmission declines rapidly and disappears after eight days.
Jin Su Song, MD, MPH, DTMH, an infectious disease specialist working at the Korea Centers for Disease Control and Prevention, said his team observed that Omicron’s infectivity completely disappeared after 10 days. South Korea’s current quarantine guidance is 10 days.
“We don’t know exactly how long [infection] Sustained,” Song told VigorTip. “Based on our research, and our preliminary research, the duration of infection may be equal to or less than that of wild-type virus or Delta virus. ”
When should you test?
If you have been exposed to someone who has tested positive for COVID-19, it is wise to test two to four days after exposure, given Omicron’s incubation period.
PCR tests have a lower threshold and can detect the virus before the infectious period, making it more accurate to detect those who are already infected, even if they are asymptomatic.
Daniel Larremore, Ph.D., assistant professor at the University of Colorado Boulder, said that while PCR testing remains the “gold standard” for clinical diagnosis, delay may be a trade-off not worth the increased accuracy for large-scale testing. test program.
“PCR tests are often delayed by a day or more due to high demand, which means that even though PCR is more sensitive to detect early infection, the information returns over a considerable period of time, essentially erasing much of the ‘warning’ ‘Value that’s what people might hope for,’ he wrote in an email to VigorTip.
Should I use PCR or rapid testing for COVID-19?
If you have a PCR test, it is important to isolate until you get your results to prevent potential spread to others.
The high sensitivity of PCR tests means they can also be positive in the post-infection period, after a person has recovered and is no longer infectious. Therefore, a negative antigen test and a positive PCR may mean that you are about to be infectious, or that you are no longer infectious. In this case, exposure time can help determine what stage a COVID-positive person is at.
what does this mean to you
If you test positive, isolate until your symptoms subside or for 10 days. If you receive a negative rapid antigen test after five days, you are likely no longer infectious, and you can end your isolation as long as you wear a tight-fitting mask around other people as per current CDC recommendations.
The information in this article is current as of the date listed, which means that you may have updated information as you read this article. For the latest updates on COVID-19, visit our Coronavirus news page.