As questions of how many people the second Dallas nurse infected during her journey to and from Dallas throw scary possibilities, a WHO situation assessment report gives more cause for concern by stating that the incubation period of the virus has been seen to extend to as long as 42 days in some cases. It says that recent studies conducted in West Africa have demonstrated that 95% of confirmed cases have an incubation period in the range of 1 to 21 days; 98% have an incubation period that falls within the 1 to 42-day interval. For WHO to declare an...