A 21 day quarantine, after being infected with the Ebola virus, has become the standard quarantine recommendation for avoiding the spread of the virus. That's not long enough to eliminate the risk, suggested a new study published yesterday in PLOS Currents: Outbreaks.
By looking at data from past Ebola outbreaks, as well as the first nine months of the current Ebola outbreak, Drexel University environmental engineering professor Dr. Charles Haas pointed out that between 0.1 and 12 percent of the time, the incubation period for someone infected with Ebola was longer than 21 days, either by a few days or even a couple of weeks. The 0.1 figure comes from the 1976 Ebola outbreak in Zaire, which had far fewer cases analyzed than the other Ebola outbreaks looked at in this study that have had a higher number of cases with longer incubation periods, such as the Ebola outbreak in Congo in 1995 and the current outbreak in West Africa. In the first nine months of the current Ebola outbreak in West Africa, five percent of patients had an incubation period beyond 21 days, according to WHO Ebola Response Team in a study published in the New England Journal of Medicine.
"While the 21-day quarantine value, currently used, may have arisen from reasonable interpretation of early outbreak data, this work suggests reconsideration is in order and that 21 days might not be sufficiently protective of public health," wrote Haas in the study.
The Ebola incubation period, which is the period between virus onset and symptom display, is on average two to 21 days, according to World Health Organization. Death or recovery typically follows right behind that. Once someone recovers from Ebola, they can no longer spread the disease (though it may be present in semen for up to three months), according to the Centers for Disease Control and Prevention (CDC). Most people don't deviate from that two to 21 day incubation period, as this study shows, and many don't see a doctor before symptoms arise, making a 21 day isolation sufficient for most. But with this current Ebola outbreak, which has claimed more than 4,000 lives and which has an increasing number of people being quarantined before symptoms arise, one way to get ahead of this virus may be by setting a longer quarantine period, so those who survive it may not spread it to others toward the end of the incubation period, Haas suggested in the study.
How long Ebola patients should be isolated is not answered by Haas. The purpose of the study was to not provide a number, but to start the conversation.
