In 1969, an American missionary nurse named Laura Wine came down with a troubling fever while working in the Nigerian town of Lassa. The local doctors thought it was probably malaria, but Wine didn’t respond to the usual treatments. She eventually died. Shortly after, two more nurses contracted the same mysterious disease. One also died. The other, Lily Pinneo, was evacuated to Columbia-Presbyterian Hospital, and survived. From her blood, and those of her colleagues, scientists isolated a new virus, which they named after the town where the infections began.
Since then, scientists have learned a lot about Lassa fever, and the virus that causes it. They discovered that it resides within the multimammate mouse and jumps into people who eat food contaminated by the rodent’s waste. They’ve shown that it is common in West Africa, and causes many thousands of cases every year.
But for all that knowledge, no one knows exactly why this disease, which simmers gently in Nigeria from year to year, has recently come to a dramatic boil.
It’s hard to say exactly who has Lassa fever, because early symptoms are generic, and resemble conditions like malaria and typhoid. But according to figures from the Nigerian Center for Disease Control, laboratory tests have confirmed that in the first two months of 2018, at least 317 people have been infected, and at least 64—around 20 percent—have died. (Eight further deaths are probably linked to Lassa, but haven’t been confirmed.) By contrast, there were just 143 lab-confirmed cases in all of 2017, and just 101 in 2016.