(Reuters) - Sex could keep the Ebola epidemic alive even after the World Health Organization (WHO) declares an area free of the disease, one of the discoverers of the deadly virus said on Tuesday. The WHO is hoping to announce later this week that Nigeria and Senegal are free of Ebola after 42 days with no infections -- the standard period for declaring an outbreak over, twice the maximum 21-day incubation period of the virus. However, it appears the disease can last much longer in semen. "In a convalescent male, the virus can persist in semen for at least 70...