As it spreads around the world and countries seek to contain it, researchers are also trying to better understand it. Now, a new study estimated the incubation period of the disease at 5.1 days, a key piece of knowledge to try to stop the outbreak.

The findings would indicate that the 14-day quarantine period used by many countries for people that might have been exposed to the virus is reasonable.

Researchers from the Johns Hopkins Bloomberg School of Public Health said that up to 97.5% of the individuals that develop symptoms of coronavirus do so within 11.5 days of exposure. They estimated that for every 10.000 people under quarantine, only 101 would develop symptoms after being released.

Senior author Justin Lessler and his team looked at over 180 cases from China and other countries that had been detected before February 24. A large part of the cases involved travel to or from Wuhan, the city where the outbreak started, or exposure to individuals from Hubei province, of which Wuhan is the capital.

“Based on our analysis of publicly available data, the current recommendation of 14 days for active monitoring or quarantine is reasonable, although with that period some cases would be missed over the long-term,” said Lessler, an associate professor in the Bloomberg School’s Department of Epidemiology.

The outbreak of the coronavirus emerged back in December and has already resulted in 111,275 cases around the world and 3,882 deaths from pneumonia. Most cases were recorded in the Wuhan and the Hubei province, but more than a dozen other countries are also affected, mainly Italy, Iran, and South Korea.

The fact that researchers were able to estimate the incubation period of the virus is a significant step forward, as it will be easier for epidemiologists to measure the dynamics of the outbreak and for governments to develop more effective quarantine and control measures. Quarantines’ main goal is to restrict the movement of people exposed to the disease even if they haven’t tested positive. Quarantines can successfully slow and can even stop the spread of the infection but have costs, as people are prevented from going to work in most cases.

The Centers for Disease Control and Prevention (CDC) in the US has said a quarantine means not going to work, school, or public areas, as well as avoiding the use of public transportation and taxis. If you share your home with other people, being in a separate room is advisable.

The 5.1 days incubation period of the coronavirus is in line with earlier studies of the virus. The number of days is also similar to the SARS-CoV, a different type of virus that affected China and Hong Kong from 2002 to 2004, and to the MERS-CoV, a coronavirus that affected the Middle East in the past.