The measles used to be one of the world’s most common childhood diseases. Since the introduction of the measles vaccine, however, the disease is rarely seen in the U.S. But people have a reason to still feel cautious about what might seem like an old-timey affliction: Between January and July 14, 2018, there were 107 reported cases of the measles across 21 states and Washington, D.C. The year before, 118 people from 15 different states (and D.C.) contracted the disease. Here are seven things to know about the infectious respiratory illness.
1. EVERYONE USED TO GET IT.
There was a time not so long ago when getting measles was a near ubiquitous part of childhood. In the 4th century CE, Chinese alchemist Ko Hung wrote of the differences between smallpox and measles, and the disease was described in the 9th century by the famous Persian physician Rhazes. There were major epidemics of the disease in the 11th and 12th centuries [PDF].
In the years before the first licensed measles vaccination appeared in the U.S. in 1963, an estimated 90 percent of children caught the measles before they were 15. The disease was a leading cause of death for children—and in some places without access to vaccinations and medical care, it still is. Today, up to 5 percent of children in places without access to good medical care die of the measles annually.
The CDC estimates that prior to the existence of the vaccine, there were between 3 and 4 million measles cases in the U.S. per year, approximately 400 to 500 of them fatal—but vaccinations have reduced the prevalence of the disease by 99 percent. In some years, less than 100 people contract the disease in the U.S.
2. IT’S HIGHLY CONTAGIOUS.
The measles virus is considered one of the most contagious viruses around: Without vaccination, around 90 percent of people who are exposed to the virus will become infected.
The disease is caused by the spread of a type of virus called morbillivirus, which can spread through the air via breathing, coughing, or sneezing. The virus can live in the air for up to two hours after an infected person coughed—meaning that you don’t necessarily need to be standing next to someone with the measles to get it from them.
3. IT CAN CAUSE MORE THAN JUST A RASH.
A person exposed to measles will begin to show symptoms seven to 14 days after exposure. The disease presents itself with symptoms like coughing, congestion, fever, and most famously, a full-body skin rash. But a third of measles cases involve complications ranging from diarrhea to pneumonia, brain swelling, and coma. Pneumonia causes around 60 percent of fatalities when it comes to measles complications.
Children under 5 are particularly at risk of getting complications and dying from the disease. One in 10 will contract an ear infection, possibly leading to permanent hearing damage, and one in 20 will get pneumonia. One or two out of every 1000 kids who contract the measles will die, according to the CDC, many from pneumonia
4. THE VACCINE IS VERY EFFECTIVE.
The measles is combined with vaccines against two other diseases—mumps and rubella—and when administered as designed, it's incredibly effective. Experts recommend that children get their first dose of the MMR vaccine on their first birthday (but not before). Then, they should get the second dose before they enter kindergarten. If a child doesn’t get vaccinated before they’re 12, they should still get the vaccine: two doses a month apart. In most cases, those two doses of the vaccine should be enough to give you immunity for life (although some experts are now cautioning booster shots may be a good idea for some adults).
If you’re exposed to the virus and haven’t been vaccinated, an immediate dose of the vaccine can provide some protection from the disease, as long as you get it within 72 hours of exposure.
5. IT’S CONSIDERED ELIMINATED IN THE U.S. …
Thanks to effective vaccinations, as of 2000, measles is no longer a threat in the U.S., according to the CDC’s standards. The disease is considered eliminated, which means that it hasn’t been continuously transmitted in a specific geographical location for at least a year. So even if there’s the occasional outbreak of cases, it’s considered eliminated because it’s not a constant threat anymore. In 2016, the World Health Organization declared the disease to be eliminated across the entirety of North and South America.
6. ... BUT YOU SHOULD STILL GET VACCINATED.
Measles isn’t prevalent in the U.S., but that doesn’t mean you can skip your vaccinations: Though home-grown measles has been eliminated, people in the U.S. still come down with it. That’s because measles is still a major issue elsewhere in the world, and travelers can bring it home with them, spreading it to unvaccinated populations in the U.S.
That includes babies. Children under 5 are one of the most vulnerable populations when it comes to measles infections, but babies aren’t generally vaccinated until they’re 12 months old (the CDC recommends that before international travel, “infants 6 months through 11 months of age should receive one dose of MMR vaccine” and then get a shot again when they’re a little older). That makes it incredibly important for everyone around them to be vaccinated, so that the disease can’t spread.
In addition to inoculating individuals against diseases, vaccines operate on the principle of herd immunity. When nearly an entire population is vaccinated, it’s very hard for the disease to spread. That protects people who aren’t inoculated, like babies, or people whose bodies didn’t respond to the vaccine for whatever reason.
7. PEOPLE STILL GET MEASLES IN AMERICA.
Since measles was declared eliminated in 2000, there have been relatively few cases reported here, but a significant number of people have caught the disease in the past few years. In 2004, there were just 37 cases of measles reported in the U.S. Ten years later, in 2014, there were 667—most of whom were people who weren’t vaccinated. (That number was unusually high, and went down to 188 cases the next year.)
The CDC blames recent measles outbreaks on low rates of vaccination. One 2016 review of measles studies found that out of 970 measles cases, almost 42 percent of patients had opted out of getting the vaccine for non-medical reasons.
Europe has also seen a surge in measles cases in the last few years. Between 2016 and 2017, measles cases in Europe quadrupled, from 5273 cases to more than 21,000, according to the World Health Organization. Thirty-five of those 21,000 people died from the disease. This is bad news for Americans, too, since most U.S. measles cases can be linked back to travelers coming into the U.S. from places like Europe. So get your vaccinations!