Throughout the month of December, Public Health Matters is conducting a series of year-in-review posts of some of the most impactful disease outbreaks of 2015. These posts will help explain how CDC is working to prevent, identify, and respond to these outbreaks.

Measles in Disneyland

After an uncharacteristically high number of measles cases in late 2014, the highly publicized California measles outbreak hit the media early this year. Linked to Disneyland Resort Theme Parks in California the outbreak quickly became a multi-state public health incident that resulted in a total of 147 cases. Cases related to this outbreak were identified in seven states in the U.S., as well as Mexico and Canada.

Attention to this outbreak was further fueled by the interest surrounding vaccinations. Among the reported measles cases, the majority of patients were unvaccinated or had an unknown or undocumented vaccination status.

Why a Measles Outbreak in the U.S. is a Big Deal

In 2000, the United States declared that measles was eliminated from this country. The elimination of measles in the U.S. was due to a highly effective measles vaccine, a strong vaccination program that achieves high vaccine coverage in children, and a strong public health system for detecting and responding to measles cases and outbreaks.

Before a measles vaccine became available in 1963, 3 to 4 million people in the United States were infected with measles each year, resulting in an estimated 48,000 hospitalizations and 400 to 500 deaths. Most people in the U.S. today are protected against measles through vaccination, so measles cases are uncommon compared to the number of cases before a vaccine was available. However, the risk of measles re-establishing itself as a prominent disease in the U.S. is possible—especially if vaccine coverage levels drop.

Today, measles is still endemic in many parts of the world, and measles outbreaks in the U.S. occur when measles is brought into the United States by unvaccinated travelers (Americans or foreign visitors) who get measles while they are in other countries. These travelers can spread measles to other people who are not protected against the disease, which sometimes leads to outbreaks. While the source of the Disneyland-associated measles outbreak was not identified, it is likely that a traveler (or more than one traveler) who was infected with measles overseas visited one or both of the Disney parks in December during their infectious period and infected other visitors to the park.

Measles: a Serious Sickness

Measles is extremely contagious. It is so contagious that if one person has it, 90% of the people close to the person who are not immune will be infected. You can catch measles just by being in the same room as a person with measles. Even if the infected person has left the room, the virus can live for up to two hours in an airspace where the infected person coughed or sneezed. The measles virus lives in the nose and throat mucus of an infected person, and can spread to others through coughing and sneezing.

Common symptoms of measles include, high fever, cough, runny nose, red, watery eyes, and a rash 3-5 days after symptoms begin. In some cases complications from measles can result in pneumonia, encephalitis (swelling of the brain), and death.

People at high risk for severe illness and complications from measles include, infants and children under 5 years of age, adults over the age of 20, pregnant women, and people with compromised immune systems.

What can be done to protect the public from measles outbreaks?

State and local health departments lead investigations of measles cases and outbreaks when they occur. CDC helps and supports health departments in these investigations and continually gathers data reported by states on confirmed measles cases to provide evaluation and monitoring from a national perspective.

High sustained measles vaccine coverage and rapid public health response are critical for preventing and controlling measles cases and outbreaks. It is possible to get rid of measles in the U.S. completely, but the first step is to eliminate measles from each country and region of the world. Once this happens, there will be no place from which measles can spread.

Until measles is eliminated worldwide, it remains a risk to any unvaccinated person exposed to the virus. Do your part to protect yourself, your family, and those around you from measles and make sure you and everyone in your family who is eligible gets vaccinated. The best protection against measles is measles-mumps-rubella (MMR) vaccine. MMR vaccine provides long-lasting protection against all strains of measles.

To learn more about measles, the MMR vaccine, and CDC’s efforts to reduce the number of measles case worldwide visit CDC’s Measles webpage.