Ebola

It’s one of the deadliest diseases on Earth, with a fatality rate as high as 90 percent. It’s also grotesque, sometimes causing bleeding from the eyes, ears, mouth and rectum and a bloody rash leading to a quick demise. It’s Ebola, one of a handful of illnesses that are so deadly governments consider them a threat to national security. In an epidemic that began in December 2013, Ebola infection for the first time occurred outside Africa. That provoked panic in the U.S. and Europe, but in all there were just seven cases and one death from Ebola there. In Africa, the outbreak killed more people than all previous waves combined.

In June, data from the World Health Organization suggested the epidemic may have finally come to an end. The agency warned the three hardest-hit countries — Guinea, Liberia and Sierra Leone — to remain vigilant for new infections. Since the virus can linger for some time after recovery, for example in the eyes, testes and spinal cord, infection can occur through exposure to survivors’ body fluids. About 28,600 people were infected with the disease and 11,300 died, according to the official count. Almost as many extra deaths from malaria, HIV/AIDS and tuberculosis are thought to have occurred because the epidemic reduced access to healthcare services. It also created an estimated 23,000 orphans. The World Bank calculated that the economic disruption caused by Ebola cost the three countries at least $2.8 billion in foregone economic growth in 2014 and 2015. In contrast, nations with better medical systems — Nigeria, Senegal and Mali — were able to contain Ebola when it spread there. The Democratic Republic of Congo controlled an outbreak of a different strain of the virus.