Measles is one of the most contagious diseases known. If one person has measles, up to 90% of nearby non-immune people will become infected
. In fact, one contagious person can infect 12 to 18 others in a room of unvaccinated individuals
. The virus spreads easily through breathing, coughing, sneezing, or even talking, as infected droplets can remain suspended in the air or on surfaces for up to two hours
. People are infectious from about four days before the rash appears until four days after
. Because of this high contagiousness, measles outbreaks can spread rapidly, especially in communities with low vaccination rates. Achieving herd immunity requires vaccination coverage of more than 95% in the community
. In summary, measles is extremely contagious, with a transmission rate that can infect nearly all susceptible individuals exposed to an infected person. Vaccination is the most effective way to prevent its spread
