About a month ago, health officials warned that America's measles outbreak would get worse before it got better. Now it has. On Thursday, the Centers for Disease Control and Prevention (CDC) announced there have been 971 cases of measles in the United States in 2019. This is the greatest number of cases reported in the U.S. since the last major outbreak in 1992, when there were 963 cases in the entire year.
The country may lose its official status as having "eliminated" measles—meaning there's no continuous outbreak that lasts longer than a year—CDC officials warn. Ensuring zero cases of measles in the country is impossible because the disease isn't eliminated everywhere in the world, so travelers may always carry it with them into the U.S. A high rate of vaccination helps limit how far measles spreads when it's introduced into a community, but as anti-vaccination beliefs have become more popular in some parts of the U.S., they've made certain communities vulnerable.
Nationwide, more than 90 percent of children get their recommended measles, mumps, and rubella, or MMR, shots. In certain communities, however, the rates can be much lower. For example, one large and ongoing outbreak is happening in just four ZIP codes in Brooklyn, New York, where handbooks and hotlines have spread unfounded myths about the MMR vaccine's dangers among ultra-Orthodox Jewish families, as the New York Times reported in April. Most high-profile ultra-Orthodox rabbis support and encourage vaccination, the Times reports. But because measles passes very easily between people, even a slight dip in vaccination rates can have major consequences, as Emily Moon reported for Pacific Standard:
It may seem counterintuitive, but the fact that unvaccinated people are clustered within four ZIP codes (and not spread throughout the state or city) makes the risk of vaccine-preventable illness even greater. Measles is highly contagious, and thus requires at least a 95 percent vaccination rate to maintain herd immunity. (Other diseases, like polio, require around 85 percent coverage.)
Experts aren't surprised that measles has been among the first of the vaccine-preventable childhood diseases to come back in the U.S.:
Because it's highly contagious, "measles is always the first disease to come back" when herd immunity is compromised, explains Paul Offit, pediatrician and director of the Vaccine Education Center at the Children's Hospital of Philadelphia. "It's the canary in the coal mine."
Doctors especially emphasize vaccination with measles because the disease has no cure and typically kills one or two children for every 1,000 who get sick. No one in America has died yet of measles in 2019, but in February, experts Moon spoke with were already beginning to worry:
[T]he country would need to experience a few thousand cases to see deaths today, Offit says. But for the first time in decades, the medical community sees this as a real possibility. "Children aren't dying yet from measles, but if we keep doing this and we don't realize how dangerous this game is we're playing, they might," Offit says.
Meanwhile, officials are trying various strategies to up vaccination rates in measles-affected areas, including coordinated community campaigns and summoning and fining families that don't vaccinate in Brooklyn. They seem to be working: New York City saw 60 measles cases in May, down from 157 in March and 173 in April.