Thanks for the link  Interesting reading I was only ever aware of  in context of a country being declared Ebola free eg Nigeria I had assumed it was just double the maximum  day incubation in case someone either recovers or dies without being diagnosed you have double the maximum and  times the mean  And indeed this very reference supports my theory stating   is twice the maximum incubation period  But then goes on to upend the  days by saying  have an incubation period that falls within the  to  day interval and   days  What is interesting is these exact numbers appear in NEJM but the conclusion drawn in same paper is that there is no need to monitor beyond  days  What I dont know is whether the  probability stems from the lack of confidence or accuracy in the raw epidemiological data or is a clinicalbiological fact They dont say  Nigeria was very effective in quashing it in Lagos  million people after the highly infectious index case by being very aggressive in monitoring a large number of contacts more aggressive than the US as far as I read  but only up to  days My understanding from reading some of these epidemiology studies going back to  is that the mean is around  days depending on outbreak and that actually if you are symptom free for  weeks past last contact you most likely will not get it but the third week is for insurance  I have not read of any proven confirmed case with symptom onset longer than  days past last contact  They studied this in great detail in the initial outbreaks back to  including a nurse that had a needle stick so they knew exactly when she was infected  My impression was the raw data is casebycase and they delete or otherwise lower weightings on unknown outcomes  IMO any implication in WP that you could possibly incubate longer than  days has to be well supported in data and conclusion by several sources since it would definitely cause new consternation