Measles is an ancient virus, with written accounts dating back to the ninth century. Only within the last century has the development of a vaccine begun to contain the spread of the disease. Prior to the vaccine's advent in 1963, nearly all children got measles by 15 years old, resulting in 3 million to 4 million annual U.S. cases.

Therefore, if you were born before or around 1957, you've very likely had measles.

Since then, widespread vaccination has changed everything — so much so, that in 2000, measles was declared eliminated in the U.S., meaning virtually zero cases were being found and transmitted within the country. Globally, it's estimated that measles vaccinations averted more than 57 million deaths between 2000 and 2022.

Yet, despite incredible progress and the availability of a safe and cost-effective vaccine, measles remains a global threat, resulting in 136,000 fatalities in 2022 alone. Those occurred mostly in developing countries.

Measles is a growing U.S. problem — again

Measles vaccination rates in the U.S. have been declining steadily, with the most recent statistics showing an estimated 250,000 kindergarteners behind schedule. That contributed to a record number of measles cases in 2019 — 1,274.

Thanks to social distancing and other precautions during the pandemic, measles cases subsequently declined — 13 in 2020, 49 in 2021 and 58 in 2023. But cases are starting to trend upward again — through just five months of 2024, the U.S. already has reported 139 cases.

Dr. Wesley Long, medical director of diagnostic microbiology at Houston Methodist, attributes the increase in reported cases here to both declining U.S. vaccine coverage and measles' endemic state in other parts of the world. Because of this trend, Dr. Long says it's now more important than ever to know your vaccination status and prevention options.

"Measles is one of the most, if not the most, contagious viruses that we know of," says Dr. Long. "Although measles has been largely eliminated locally in the US, a non-immune person traveling abroad to a place where measles spreads locally can easily bring it back to infect unvaccinated or vulnerable populations and cause a spike in cases."

Just how contagious is measles?

Measles is an airborne virus that spreads when an infected person sneezes or coughs and that can live for hours in the nearby air. It is much more contagious than COVID-19, according to Dr. Long, who puts its contractability into perspective.

"Let's say a person infected with measles is present in a room and then leaves," says Dr. Long. "The virus can remain for up to two hours in the air in that space and still infect non-immune people who come into contact with it despite the infected individual not being present."

Measles is so contagious that if one person has it, 90% of nearby non-immune people will become infected. Worse, people can spread measles four days before and after the onset of the most obvious sign of infection, a red, blotchy rash that starts at the head and spreads throughout the body.

"Most people aren't necessarily going to know they have measles until they see a red blotchy rash," says Dr. Long. "So they could have been spreading it for a few days' prior, and they can continue to spread it for several days after the rash appears."

What does measles look like?

Measles is much more than just a rash. In fact, the virus goes on to infect many key organs that can cause a variety of symptoms and complications. But it's not until 10 to 14 days after infection that the first signs of measles — not including the rash — start to show. Early symptoms of measles typically include:

• Cough
• Conjunctivitis (pink eye)
• Coryza (stuffy nose)

One to two days later, white dots that resemble salt grains, known as Koplik spots, may appear inside of the cheeks, followed by the onset of the measles rash, which fades after four days or so.

More severe complications such as pneumonia and bacterial superinfections (secondary, resistant infections) can arise, especially in infants and young children, the population most at risk for severe disease.

"Children younger than 5, adults older than 20, pregnant women and immunocompromised people are all at risk for severe disease and complications," says Dr. Long. "In fact, around 1 in 1,000 children with measles will develop encephalitis, or swelling of the brain, which can cause permanent brain damage, and 1-3 out of every 1,000 children will die from respiratory or neurologic complications."

Also, once someone recovers from measles doesn't mean they're in the clear, according to Dr. Long.

"Even if you get measles and recover from it, children run the risk of a rare complication that can develop 7 to 10 years down the road called subacute sclerosing panencephalitis," says Dr Long. "It's a rare, often fatal degenerative disease of the central nervous system that starts out as mood changes and intellectual deterioration but can end with seizures, coma or death."

How to know if I am immune to measles?

Good news: The vast majority of the U.S. is either immune or vaccinated at least once against measles through the MMR vaccine, a three-in-one vaccine that protects against measles, mumps and rubella, that was developed in 1971. Today, the recommended vaccination regimen is two doses: the first at 12 to 15 months of age and the second at 4 to 6 years old. However, most adults can receive the vaccine if they haven't already.

One dose of the MMR vaccine is about 93% effective at preventing measles, while two doses provide around 97% efficacy. And more than likely, your age dictates whether you received one, two or zero doses of the measles vaccine:

• If you were born before 1957, you likely had measles as a child and are immune
• If you were born between 1957 and 1975, you likely had only one dose of a measles vaccine
• If you were born after 1975, you likely received the full two doses of the combined MMR vaccine

When it comes to deciding whether you need an additional vaccine, Dr. Long says risk plays an important factor.

"It's recommended that school-age children and adults at high risk, including college students, health care personnel and international travelers receive the full two doses of MMR," says Dr. Long.

When it comes to finding your vaccine records, programs vary state to state. But besides asking your healthcare provider to see if they have a copy on file, your best bet is to contact your state's immunization information system (IIS). In Texas, for example, you can fill out a form to receive your vaccination record via email or mail.

If you're unable to locate your vaccination records and are not sure if you've been fully vaccinated, you can also have an antibody titer test that measures the concentration of measles antibodies in your blood. If there are no titers detected, says Dr. Long, then another vaccine dose may be appropriate.

That's not the case, however, for certain individuals who are immunocompromised, or have a weakened immune system.

"MMR is a live-attenuated vaccine, meaning it contains weakened versions of the virus to cause a strong immune response within the body without actually causing the disease itself," says Dr. Long. "Those who are immunocompromised, whether due to cancer, an infection like HIV or an organ transplant, should talk to their healthcare provider. It's going to depend on what their doctor recommends based on their specific health situation."

Is German measles the same thing as measles?

German measles, also called rubella, is not the same as measles, but rather another highly contagious virus that can cause serious complications when an infection occurs during early pregnancy. However, the good thing is that the current measles vaccine, MMR, covers both measles and rubella — killing two birds with one stone.

How can I get the MMR vaccine?

All private insurance plans must cover certain vaccines without charging a copay or coinsurance when provided by an in-network provider. This is true even for patients who haven't yet met their yearly deductible.

MMR vaccines are widely available — at doctor's offices, popular pharmacies, and many other health centers.

"The only real defense against measles," says Dr. Long, "is vaccination."