arstechnica.com
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Measles is one of the most infectious viruses we know of and can linger in the airspace of a room for up to two hours after an infected person has been present. Among unvaccinated people exposed to an infectious person, up to 90 percent will become ill. Many infections are only identified when measles’ telltale rash develops, but a person can be infectious for four days before that rash develops, allowing the virus to more easily spread. People remain infectious for four days after the rash appears. In newly infected people, symptoms, which also include high fevers, typically begin 7 to 14 days after exposure, but this incubation period can be as long as 21 days, which is the length of quarantine.
In its latest update, South Carolina’s Public Health Department reported data indicating that its large case jumps will continue. In recent weeks, officials have identified 23 schools where measles has been unleashed. In 20 of the schools, unvaccinated and exposed students have been identified and quarantined, with individual schools’ quarantine totals spanning 13 to 59 students. For the remaining three schools with exposures, officials are still determining how many students need to be quarantined.
State officials have also identified eight public places where measles exposures have occurred recently, including grocery stores, a US Post Office, and a skating center.
For now, 557 students are quarantined, but additional susceptible people have likely been exposed.
Among the 789 cases, 769 (97 percent) were unvaccinated or partially vaccinated or had an undocumented vaccination status. Two doses of the measles, mumps, and rubella vaccine are 97 percent effective against measles, and that protection is considered lifelong.
