Parinisti measles

From Memory Alpha, the free Star Trek reference

Parinisti measles are a medical condition humans are susceptable to.

In early 2371, six members of Voyager's crew came down with the Parinisti measles. Although it was touch-and-go for a while, the Doctor was able to isolate the endoplasmic virus, and replicate it, in order to form an antibody. And although it wasn't altogether clear that he could create an effective vaccine, he worked at it for 74 hours straight, and was successful in creating an inoculation, stopping its spread before it became an epidemic.

He told the story of this achievement to several Vikings later that year, on his first away mission in the holodeck. (VOY: "Heroes and Demons")