Measles is one of the world's most contagious viruses. Here's what to know and how to avoid it

Measles is rarely seen in the United States, but Americans are growing more concerned about the preventable virus as cases continue to rise in rural West Texas.

This week, an unvaccinated child died in the West Texas outbreak, which involves more than 120 cases. The U.S. Centers for Disease Control and Prevention said the last confirmed measles death in the United States was in 2015.

There are also nine measles cases in eastern New Mexico, but the state health department said there is no direct connection to the outbreak in Texas.

Here's what to know about the measles and how to protect yourself.

What is measles?

It's a respiratory disease caused by one of the world's most contagious viruses. The virus is airborne and spreads easily when an infected person breathes, sneezes or coughs. It most commonly affects kids.

"On average, one infected person may infect about 15 other people," said Scott Weaver, a center of excellence director for the Global Virus Network, an international coalition. "There's only a few viruses that even come close to that."

Measles first infects the respiratory tract, then spreads throughout the body, causing a high fever, runny nose, cough, red, watery eyes and a rash.

The rash generally appears three to five days after the first symptoms, beginning as flat red spots on the face and then spreading downward to the neck, trunk, arms, legs and feet. When the rash appears, the fever may spike over 104 degrees Fahrenheit, according to the CDC.

There's no specific treatment for measles, so doctors generally try to alleviate symptoms, prevent complications and keep patients comfortable.

People who have had measles once can't get it again, health officials say.

Can measles be fatal?

It usually doesn't kill people, but it can.

Common complications include ear infections and diarrhea. But about 1 in 5 unvaccinated Americans who get measles are hospitalized, the CDC said. Pregnant women who haven't gotten the vaccine may give birth prematurely or have a low-birthweight baby.

Among children with measles, about 1 in every 20 develops pneumonia, the CDC said, and about one in every 1,000 suffers swelling of the brain called encephalitis — which can lead to convulsions, deafness or intellectual disability.

It's deadly "in a little less than 1% of cases, mainly in children," said Weaver, who works at the University of Texas Medical Branch in Galveston. "Children develop the most severe illness. The cause of death in these kinds of cases is usually pneumonia and complications from pneumonia."

How can you prevent measles?

The best way to avoid measles is to get the measles, mumps and rubella (MMR) vaccine. The first shot is recommended for children between 12 and 15 months old and the second between 4 and 6 years old.

"Before a vaccine was developed in the 1960s, everybody got" measles, Weaver said. "But then when the vaccine came along, that was a complete game-changer and one of the most successful vaccines in the history of medicine."

There is "great data" on the safety and effectiveness of the vaccine, he said, because it's been around for decades.

"Any of these outbreaks we're seeing can easily be prevented by increasing the rate of vaccination in the community," he said. "If we can maintain 95% of people vaccinated, we're not going to see this happening in the future. And we've slipped well below that level in many parts of the country."

Vaccination rates have declined nationwide since the COVID-19 pandemic, and most states are below the 95% vaccination threshold for kindergartners — the level needed to protect communities against measles outbreaks.

Do you need a booster if you got the MMR vaccine a while ago?

Health care professionals are sometimes tested for antibodies to measles and given boosters if necessary, Weaver said — even if they've already had the standard two doses as a child.

He said people at high risk for infection who got the shots many years ago may also want to consider getting a booster if they live in an area with an outbreak. Those may include family members living with someone who has measles or those especially vulnerable to respiratory diseases because of underlying medical conditions.

"But I don't think everyone needs to go and run out to their doctor right now if they did receive two doses as a child," he said. "If people would just get the standard vaccination, none of this would be happening."