Amidst the spread of the current coronavirus epidemic, it can be hard to find science-based advice, as so much of the information out there is either just cautionary, or downright wrong. Thankfully, we’re getting more data on a daily basis.
Now, the latest research out of Johns Hopkins University has shown that COVID-19 has an average incubation period of 5.1 days, meaning that the 14-day quarantine period recommended by the CDC is bang on the money.
Health officials have to make important decisions based on limited information, and it’s always good to have that decision backed up with science.
The Johns Hopkins team looked at 181 cases of COVID-19 outside of Hubei province in China before February 24 this year.
Recording the time of possible exposure, symptom onset, fever onset, and detection by authorities for each case, the team created a model of the incubation period distribution.
Put simply, the incubation period is the time between when you are exposed to the disease and when you start showing symptoms. This is usually before the contagious period, when you are likely to give the disease to others.
We don’t yet know how contagious the coronavirus is when people aren’t showing symptoms, however, there have been a few reports of people transmitting the virus without showing symptoms at all.
That being said, as with other coronaviruses (such as the common cold), you are much more likely to transmit the virus to someone else while you are coughing or sneezing.
The Johns Hopkins team found that less than 2.5 percent of those infected would show symptoms within 2.2 days; the estimated median incubation period was 5.1 days; and 97.5 percent will show symptoms within 11.5 days.
“Based on our analysis of publicly available data, the current recommendation of 14 days for active monitoring or quarantine is reasonable,” says epidemiologist Justin Lessler from Johns Hopkins Bloomberg School of Public Health.
“Although with that period some cases would be missed over the long-term.”
This sort of research is incredibly helpful for infectious disease specialists who are making policy decisions for coronavirus.
There has been worries that the incubation period isn’t long enough, after other teams of researchers discovered incubation periods that lasted up to 19 and 24 days.
Extrapolating from the 181 cases, the Johns Hopkins team estimated that for every 10,000 people quarantined for 14 days, around 101 would develop symptoms after release.
More research – with larger groups of people – will have to be done to confirm whether the longer incubation periods might cause an issue for our current quarantine policies.
The research has been published in Annals of Internal Medicine.