The United States is experiencing its largest measles outbreak since the virus was eliminated in 2000. As of Monday, 839 cases of measles have been reported in 23 states, according to the Centers for Disease Control and Prevention, including seven cases in Pennsylvania.  

“Measles is not a trivial disease,” said Dr. Catharine Paules, an infectious diseases physician at Penn State Health. “It remains a leading cause of vaccine-preventable mortality worldwide and is responsible for more than 100,000 deaths globally each year.”

Although most people will recover from it, about one in four with measles with be hospitalized and one or two in 1,000 will die of the disease.

Patients with measles may develop pneumonia (the most common cause of death from measles) and encephalitis, brain swelling that can lead to convulsions or long-term disabilities. 

Additionally, subacute sclerosing panencephalitis (SSPE) is a very rare but fatal disease of the central nervous system that results from a measles virus infection acquired earlier in life. SSPE generally develops 7 to 10 years after a person contracts measles, even though the person seems to have fully recovered from the illness. “That’s the one complication of measles that worries me the most,” Paules said.

“The only way to prevent measles reliably is to get vaccinated,” she added.

Not everyone is able to get the vaccination nor does everyone respond to the vaccine. These are often people at high risk of measles complications and death. They include babies, pregnant women and people with weakened immune systems.

“We need to make sure these individuals stay healthy,” Paules said. “By getting vaccinated, we protect ourselves individually, and also help protect the public from measles.”

The measles vaccine is 97% effective, which makes it one of the most effective vaccines. In the U.S., thanks to the effectiveness of this vaccine and strong public health initiatives, measles was eliminated in the year 2000. This is defined as no sustained transmission for more than 12 months.

Elsewhere in the world, however, measles cases are still occurring.  

“Measles is a problem with a clear scientific solution, but we have taken a clear step back in measles elimination and eradication,” Paules said. “Worldwide we have seen a 31% increase in measles cases.”

Measles is highly contagious. Someone not immune to the virus has a 90% chance of being infected if they are exposed. Additionally, one infected person could spread the disease to as many as 18 others in a population that is not immune. So, high levels of vaccination coverage — more than 93% — are needed to stop the spread of measles.

In the U.S., travel is helping measles’ resurgence.

“Travelers come back with measles because they are not immune,” Paules said. They then spread the disease to others who aren’t immune. “It’s important to talk to your doctor if you’re making international travel plans. See what your vaccine status is, and if you need another dose of the vaccine.”

 “If you’re unsure whether you are protected against measles, go talk to your doctor,” Paules said. “You may need to receive a measles vaccine, and sometimes lab work may be helpful to determine whether you are immune.”   

Learn more:

• The Medical Minute: Immunization the best defense against measles
• The Medical Minute: Vaccinations are not just for kids

The Medical Minute is a weekly health news feature produced by Penn State Health. Articles feature the expertise of faculty, physicians and staff, and are designed to offer timely, relevant health information of interest to a broad audience.