Chinese scientists have come up with a new estimate for the incubation period of Covid-19, which is around 7.76 days, longer than previous estimates of 4 to 5 days.
The study, published in the journal Science Advances, involves the largest amount of coronavirus patient samples to date.
By providing health authorities with a potentially more accurate figure for the incubation period, the results could inform guidelines for containment efforts such as quarantines and studies investigating the disease’s transmission.
“Countries and health authorities have implemented various containment measures such as quarantines to slow the spread of Covid-19,” the Chinese researchers wrote.
“To work effectively, these strategies depend on understanding the disease’s incubation period, or the time between someone becoming infected and showing the first symptoms of the disease, and how much it varies from individual to individual,” they added.
However, researchers lack a reliable estimate of the incubation period of Covid-19.
The few existing estimates of 4 to 5 days were based on small samples sizes, limited data, and self-reports that could be biased by the memory or judgement of the patient or interviewer.
For the current findings, the research team developed a low-cost approach to estimate incubation periods and applied it to 1,084 confirmed cases of Covid-19 that had known histories of travel or residency in Wuhan, China.
Their approach improves accuracy by relying on a public database of dates of infection and uses the renewal theory in probability to reduce recall bias — the inaccurate recollection of past events.
Ultimately, the team calculated that the median incubation period was 7.75 days, with 10 per cent of patients showing an incubation period of 14.28 days.
The authors noted that this last finding may concern health authorities relying on the standard 14-day quarantine, but caution that their approach relies on several assumptions and may not apply to later cases where the virus may have mutated.