As of January 30, 2015, 91 cases of measles have been reported in California, and 59 of those are linked to the Disneyland measles outbreak. So much for being the place where dreams come true.
While this current outbreak is upsetting, and another reason for anti-vaxxers to shut up already, measles is a much bigger problem globally than it is in the United States. As with most infectious diseases that aren’t common here, there’s a lot of misunderstanding about what measles is and how dangerous it can be. Here’s a little Measles 101, sourced from WHO, CDC, and reputable scientific journals.
How serious is measles? In 2013, WHO reported 145,700 measles deaths worldwide--that’s about 16 deaths per hour, every day. Prior to 1980, when vaccination became widespread, WHO estimates there were 2.6 million measles deaths per year.
But I thought it wasn’t much worse than chicken pox! Well, there’s a rash and fever. But the complications are what make measles so frightening. Blindness, encephalitis, and pneumonia are a few of the serious complications. Severe measles is more likely among populations who are under age five or over age 20, undernourished (particularly with a vitamin A deficiency), or who have weakened immune systems.
How is measles transmitted? The measles virus can stay alive, airborne or on a surface, for two hours. People who have been infected are contagious for four days prior to the emergence of a rash, and for four days after the rash appears. Historically, each person infected with measles will infect between 11 and 18 other people, though there is some evidence that measles is becoming slightly less contagious in recent years. (This is a really awesome explanation of R0, R, and eliminating infectious diseases. Public health nerds, unite!)
But I thought measles was eliminated from the United States. Technically, as of 2000, it is. All elimination means is that a virus no longer regularly circulates through the population--its theoretical incidence in a geographic area is 0. But that doesn’t mean that measles no longer exists on Earth, so it’s easy for measles to guest star in an outbreak here and there. In 1989-1991, there was a particularly nasty outbreak in the United States in which about 55,000 people were infected, resulting in 11,000 hospitalizations and 123 deaths.
How can I avoid getting measles? Get the MMR vaccine. It doesn’t cause autism, and a 95% of people who get a single dose are immune to measles, mumps, and rubella. A second dose closes the gap, and close to 100% of people who get two doses of the MMR vaccine are protected against all three viruses. Yeah science!