People infected by novel coronavirus tend to develop symptoms about five days after exposure, and almost always within two weeks, according to a study released Monday in the journal Annals of Internal Medicine.
That incubation period is consistent with previous estimates from public health officials, and the findings suggest that 14 days of quarantine are appropriate for people potentially exposed to the coronavirus.
The US Centers for Disease Control and Prevention has used that standard during the current pandemic — recommending, for example, that people self-quarantine for two weeks after traveling to countries with widespread coronavirus transmission, such as Italy or South Korea.
To estimate the incubation period, researchers scoured more than 180 reports of coronavirus in places without widespread transmission of the virus — areas, in other words, where infection was likely due to outside travel.
Because the study was conducted early in the coronavirus epidemic, community transmission at the time was limited to Wuhan, China. That allowed researchers to estimate the “time of exposure” to the coronavirus by determining when a person was in Wuhan — the only plausible source of infection. By comparing travel to Wuhan with the emergence of symptoms, researchers could then estimate an incubation period for the virus: usually about five days, and rarely more than 12.
It’s possible, the researchers said, that their study may have focused on more severe cases of the virus – which are likelier to make the news and catch the attention of public health officials. The incubation for mild cases, then, might differ somewhat.