Some people think of measles as a simple childhood illness that causes an itchy rash. But measles is a very contagious disease that can result in some serious complications.
Measles is making headlines because of an outbreak in Washington state. Health officials have declared a state of emergency with dozens of confirmed cases reported. Most of the cases are in Clarke County, which borders Portland, Oregon, and most of the patients are children who have not been vaccinated, reports CBS News.
(Measles is also called rubeola, so it's worth noting a common misunderstanding: Rubeola and rubella — though spelled similarly — are not the same disease. As the Mayo Clinic explains, they are caused by different viruses and both involve a rash, but that's where the similarity ends.)
Here's what to know about measles, which has been in the headlines so much lately.
How do people get measles?
Measles is caused by a virus that lurks in the system of an infected adult or child. When they cough, sneeze or even talk, they spread droplets of the virus into the air around them. Other people either inhale those droplets or pick them up from a surface where they landed. Those virus droplets can remain alive and well for hours, reports the Mayo Clinic. About 90 percent of susceptible people who are exposed to an infected person will become infected with measles.
And someone may be spreading measles before they even know they are sick. For the first 10 to 14 days after you're infected, the virus incubates, meaning you have no signs of the illness.
What are the symptoms of measles?
About 10 days or so after you're exposed to the virus, you might notice a high fever, a cough, runny nose and red, watery eyes. Two or three days after symptoms start, you'll likely notice tiny white spots inside your mouth. A few later, an irritating rash will spread across your body, usually beginning on your face and hairline and spreading to your neck, torso, arms, legs and feet. It can start as flat, red spots and later become raised bumps. Symptoms usually last just a few days, but it could take a few weeks for you to recover from fatigue.
What happens if symptoms get worse?
Children under 5 and adults over 20 are more likely to develop complications from measles. One out of every 20 children with measles will get pneumonia (the most common cause of measles-related death) and one out of every 1,000 will develop encephalitis or swelling on the brain, according to the Centers for Disease Control and Prevention (CDC). Other possible complications include ear infections, severe diarrhea, bronchitis, laryngitis and croup.
How is measles treated?
There's no specific treatment for measles, so your best bet is to try to ease your symptoms. Get plenty of rest and drink lots of fluids. Take an over-the-counter medicine like acetaminophen or ibuprofen to reduce a fever. Never give aspirin to a child or teenager with flu-like symptoms because aspirin has been linked to the rare but life-threatening Reye's syndrome.
How effective is the measles vaccine?
The measles vaccine is very effective, according to the CDC. One dose of the vaccine is about 93 percent effective at preventing measles if you are exposed to the virus and two doses are about 97 percent effective.
Only about three out of 100 people who have had two doses of the vaccine will get measles if exposed to the virus. Why do some people get measles even after getting vaccinated? Experts think maybe their immune systems didn't react like they should have to the vaccine. But fully vaccinated people will have milder symptoms and are less likely to spread the disease to other people.
What happened before the measles vaccine?
Health care providers in the U.S. didn't start reporting measles cases until 1912, according to the CDC. When they did, there was an average of about 6,000 measles-related deaths each year. In the decade before the measles vaccine was made available to the public in 1963, almost all kids got the measles by the time they were 15. There were about 3 to 4 million cases each year with an estimated 48,000 hospitalizations and 400 to 500 deaths.
What impact did the vaccine have?
In 1968, an improved, weaker measles vaccine was distributed and this is the one still in use. The measles vaccine is usually combined with mumps and rubella (called MMR), or with mumps, rubella and varicella (MMRV). By 1981, measles cases had dropped to 80 percent fewer than the year before. Measles outbreaks in 1989 among schoolchildren who had been vaccinated prompted many medical groups, including the American Academy of Pediatrics, the American Academy of Family Physicians and the Advisory Committee on Immunization Practices, to recommend a second dose of MMR vaccine for all children.
In 2000, measles was declared eliminated in the U.S., meaning there was no continuous disease transmission for more than 12 months, reports the CDC.
If measles has been eliminated, where did these cases come from?
Even if a disease is considered eradicated from an area, it doesn't mean it will never appear there again. Travelers can bring it back when visiting other countries where the illness thrives, and that's what is believed to have happened with measles outbreaks. Then, once the virus enters the U.S. it is spread, particularly in communities where there are large numbers of unvaccinated people, according to the CDC.
How many people skip the measles vaccine?
According to the CDC, 91 percent of children got the MMR vaccine in 2016, the latest year for which statistics are available. That's almost enough for "herd immunity" or "community immunity," which means that enough people in a community are protected to keep germs from spreading and getting other people sick. To get herd immunity from measles, about 93 to 95 percent of people need to be vaccinated, reports WebMD.
"The whole principle is if you give a vaccine to somebody, you protect them from getting infected, but you also prevent them from transmitting the disease to other people," Michael Brady, M.D., associate medical director at Nationwide Children's Hospital in Columbus, Ohio, and a member of the hospital's Division of Infectious Diseases, tells WebMD.
In the case of measles, there are places throughout the country where vaccine refusal rates are exceptionally high. All 50 states require certain vaccines for students, but all school laws grant exemptions for medical reasons and almost all states grant exemptions for people who are against vaccines for religious reasons, according to the National Conference of State Legislatures. In addition, 18 states allow exemptions for people who object to vaccines for personal or moral beliefs. Only California, Mississippi and West Virginia do not allow religious or personal-belief exemptions.
Editor's note: This article has been updated since it was originally published in January 2019.