In Which the News is Good

 Posted on October 27, 2014 in Uncategorized

Dallas's index Ebola Zaire patient, Thomas Duncan, was at home for four days while he was symptomatic with Ebola. His family were not infected with the virus.

While Duncan infected two nurses at the hospital during his final days (when he was leaking blood from every available orifice) he didn't infect the people who lived with him when he was very sick-sick enough to have gone to the hospital and been sent away.

One of the commenters on my last Ebola post pointed out that Ebola has a very low basic reproduction number, R 0, of about two. R 0 is not an inherent characteristic of a virus, but depends on the environment. The R 0 for Ebola Zaire has been calculated as 2.7 in some outbreaks, but 2.0 in this one in Africa. As long as R 0 is greater than one, the disease will continue spreading. If R 0 were intrinsic, Ebola Zaire would continue spreading until eventually everyone got sick. Fortunately, R 0 will be lower in a more developed nation than in the Third World.

Given that neither of the people whom we know Duncan to have infected appears to have infected anyone else, R 0 for Ebola Zaire in Dallas in 2014 is something less than one (2/3?).

What about the scary transmission through the air? The good thing about that is that Ebola doesn't make you cough or sneeze. So while an infected person can, contrary to the government's assertions, transmit the virus through the air, it's not a mode of transmission of which the virus has evolved to take advantage (contrast a cold or flu virus, which spreads by making you expel virus-laden particles at high velocity through your mouth and nose).

So I'm downgrading my concern about Ebola in the U.S. from "do something now" to "play Whac-A-Mole as cases appear."