What condition marks the end of a national Ebola outbreak?

What condition marks the end of a national Ebola outbreak?

• A. All cases fully recovered
• B. 42 days after the last patient in isolation tests negative for the virus
• C. Population-wide immunity is achieved
• D. No new cases reported for a year

Answer: (B)

The end of an Ebola outbreak is declared after a defined surveillance window that reflects how long the virus could be transmitted and when new cases would be expected to appear. Ebola’s incubation period is up to about 21 days, so watching for a full two incubation periods without any new cases provides strong evidence that transmission has stopped. That’s why the criterion used is 42 days after the last patient in isolation tests negative for the virus—the time needed to be confident no one is developing or could develop Ebola from that chain of transmission. Reaching that 42-day mark isn’t just about the last patient recovering; it also relies on ongoing surveillance and testing to ensure no undetected cases emerge. Only after this period, with no new cases, is the outbreak considered over. Other options don’t fit because recovering everyone doesn’t guarantee there’s no remaining transmission, population immunity doesn’t guarantee elimination of new cases, and waiting a full year is unnecessarily long given the virus’s incubation dynamics.

The end of an Ebola outbreak is declared after a defined surveillance window that reflects how long the virus could be transmitted and when new cases would be expected to appear. Ebola’s incubation period is up to about 21 days, so watching for a full two incubation periods without any new cases provides strong evidence that transmission has stopped. That’s why the criterion used is 42 days after the last patient in isolation tests negative for the virus—the time needed to be confident no one is developing or could develop Ebola from that chain of transmission.

Reaching that 42-day mark isn’t just about the last patient recovering; it also relies on ongoing surveillance and testing to ensure no undetected cases emerge. Only after this period, with no new cases, is the outbreak considered over.

Other options don’t fit because recovering everyone doesn’t guarantee there’s no remaining transmission, population immunity doesn’t guarantee elimination of new cases, and waiting a full year is unnecessarily long given the virus’s incubation dynamics.