Measles, also known as rubeola, is a disease caused by a virus, specifically a paramyxovirus of the genus Morbillivirus (Realm: Riboviria, Kingdom: Orthornavirae).
Measles is spread through respiration (contact with fluids from an infected person's nose and mouth, either directly or through aerosol transmission), and is highly contagious—90% of people without immunity sharing a house with an infected person will catch it. Airborne precautions should be taken for all suspected cases of measles.
The incubation period usually lasts for 4–12 days (during which there are no symptoms). Infected people remain contagious from the appearance of the first symptoms until 3–5 days after the rash appears.
Measles in The Disunited States of America
The nation-state of Ohio released a tailored version of the measles into Virginia in its opening move in the Ohio-Virginia War of 2097. This version was more contagious than more natural strains, and had a fatality rate of almost 100%. The resulting panic and death left Virginia vulnerable to a ground invasion.
Measles in Household Gods
In AD 170, the Roman town of Carnuntum was devastated by a mysterious pestilence, which ultimately killed about a third of the population. The time-displaced mind of Nicole Gunther, inhabiting the body of her ancestor Umma, recognized the symptoms of measles, though the disease was unknown to the Romans and had no Latin name. Nicole remembered hearing that Native Americans died in droves because they had no immunity to the common diseases brought by European colonists, and realized that the same danger could happen here. While Nicole's body had had measles as a child in 20th-century Indiana, and was therefore immune, it had been left in Los Angeles in 1999. Umma's body had no such protection, therefore Nicole had to be extremely careful while inhabiting it. Ultimately, Nicole-in-Umma survived, but saw several close friends, relations, and other people in her inner circle dead from the disease.