Ebola, in contrast, has a high mortality rate (up to 90%) but is spread only through intimate contact with bodily secretions such as vomit, blood or feces. There is no risk in sitting next to an infected traveler on an airplane. In principle, therefore, transmission can be prevented by isolating people with the disease.

About 70% of emerging infectious diseases, including HIV/AIDS, West Nile, influenza, SARS, MERS and Ebola, are animal infections that have jumped to humans, frequently through a domesticated animal. Pigs are a common intermediate for respiratory viruses including influenza. Opportunities for such cross-species jumps are increased by the loss of wildlife habitat to development as well as the human consumption of bushmeat due to poverty or cultural preference. A warming climate may also increase the geographic range of insects like mosquitoes and ticks that can carry diseases such as dengue, malaria and chikungunya. By analogy to a related virus, Marburg, scientists presume that Ebola originated in bats, although there is no proof…

An infected individual could board a flight in West Africa, become symptomatic in the air or after landing and then expose others to the virus. At worst, this might result in a few other people becoming infected and possibly dying. But sustained outbreaks would not occur in the U.S. because cultural factors in the developing world that spread Ebola—such as intimate contact while family and friends are caring for the sick and during the preparation of bodies for burial—aren’t common in the developed world. Health authorities would also rapidly identify and isolate infected individuals.