Tuesday, October 21, 2014

WHO articles seem to self-contradict on the 21-day Ebola incubation period


The World Health Organization is still saying that the official incubation period for Ebola is 2 to 21 days, despite the idea that it takes 42 days for a country to be declared Ebola-free.  The basic link is here
   
However, in another link , WHO explains the “42 days” concepts for countries, and suggests that there is an asymptotic drop off of probability of disease after 21 days.  Symptoms are still possible, if unlikely after 21 days.   One concern is that low exposures might lead to longer incubations.


There are also some reports that some, perhaps many, people in west Africa develop protective antibodies without ever becoming ill, and that milder cases or low-symptom cases may actually occur naturally. 

An important advance would be the ability to detect infection before symptoms with very low virus loads, perhaps by detecting infected monocytes, or maybe with some sort of “Andraka test” (the medical equivalent of a “Turing test”).  With HIV, Western Blot was more effective than Elisa in detecting early infection back in the 1980s.  The same idea might work here.  Patients (usually health care workers or possibly family caregivers) with early infection could be aggressively treated with anti-viral drugs to prevent symptoms.  Could this work? 

As soon as a vaccine is available, it should be given to health care workers and to residents of West Africa first.  

Richard Preston, author of "The Hot Zone" in the 1990s, has explained how the virus mutates quickly, but so far the diagnostic tests seems to be keeping up with it.
    
The US government now plans to require travelers from West Africa to land at one of five airports with medical screening, which seems porous.  Should VISAs be revoked temporarily?  I think a modified travel ban could work in the short run until the epidemic has crested.  

Wikipedia attribution link for Ebola epidemic map. 

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