You are most likely to spread the coronavirus to someone else two days before and three days after your COVID-19 symptoms start to appear, according to a new study from Boston University.

The study — published in the journal JAMA Internal Medicine in August — discovered the timeline after studying COVID-19 transmissions among about 9,000 close contacts of primary COVID-19 cases in Zhejiang province of China from January 2020 to August 2020.

  • The researchers found the “close contacts” were infected shortly before or after the primary individual developed notable symptoms of the coronavirus.
  • The study found that infected people were most likely to be asymptomatic if they were infected by someone who was asymptomatic, too.
This COVID-19 symptom might not go away for those over 40 years old
Most COVID-19 survivors experience these COVID symptoms, new Wuhan study says
Could Merck’s new COVID-19 pill be a pandemic game changer?

Leonardo Martinez, assistant professor of epidemiology at the School of Public Health at Boston University, said symptoms are important to preventing infection.

“Our results suggest that the timing of exposure relative to primary-case symptoms is important for transmission, and this understanding provides further evidence that rapid testing and quarantine after someone is feeling sick is a critical step to control the epidemic,” Martinez said.

The Centers for Disease Control and Prevention has said that you can develop symptoms within two to 14 days after exposure to the coronavirus. But the period of infectiousness to others remains unclear.

  • The danger from the coronavirus has only increased with the delta variant, which has been shown to make people sicker quicker, as I wrote for the Deseret News.

Dr. Rochelle Walensky, the director of the CDC, said back in August that the delta variant infects more people than previous strains of the coronavirus, and it moves faster, too, according to MarketWatch.

  • “The delta variant is highly contagious,” she said. “To put this in perspective: if you get sick with the alpha variant, you could infect about two other unvaccinated people. If you get sick with the delta variant, we estimate that you can infect about five other unvaccinated people — more than twice as many as the original strain.”