Measles cases are spiking around the U.S. this year with confirmed cases in Colorado and large outbreaks in Texas and New Mexico and elsewhere.

Measles is very dangerous because it’s so contagious — more so than other infectious diseases from COVID-19 to flu to polio and even Ebola.

The disease is especially harmful to young children. It can cause very serious illnesses and fatalities. So far this year, the worst outbreak in the U.S. has been in Texas where hundreds of people have been infected and two children have died.

“Measles is not, and never was, a benign illness,” said UCHealth’s senior medical director for infection control and prevention, Dr. Michelle Barron.

Barron is keeping a very close eye on measles cases in Colorado and outbreaks elsewhere since the disease can be so harmful.

“Measles can be deadly in children, and many people end up hospitalized. They’re very sick. It can be quite frightening,” said Barron, who is also a professor of medicine and infectious diseases at the University of Colorado School of Medicine on the Anschutz Medical Campus.

Barron is urging Coloradans to check their vaccination status and get vaccinated right away if they don’t know their vaccination history or have not been fully vaccinated for measles.

“Find out if you’re up to date on your vaccines. If you’re not, now is a fantastic opportunity to get up to date,” Barron said.

And if you think you have symptoms of measles, let your doctor know you need help.

“It’s definitely better to call ahead. We are trying to limit who gets exposed. We want to keep everyone safe, so we don’t want you sitting in a public space where you could spread the illness,” Barron said. “If they know you’re coming, they can get you right into a room. Wear a mask or put on a mask as soon as you get to the facility.”

People with measles are infectious four days before they get sick or get a rash

One of the greatest challenges to tamping down measles outbreaks is that people are infectious for as long as four days before they feel sick or get a rash. So, a person may be spreading measles without even knowing they have it.

“You may be doing all the right things, and suddenly, you get the rash,” Barron said. “You don’t know you have it until you know.”

That’s why getting the vaccine is so critical. The measles vaccine is safe and highly effective.

On top of causing the initial illness, measles is also more destructive than other infectious diseases like flu and RSV.

Barron said measles enters the body in a way that also destroys cells that protect our immune systems. The infection essentially destroys what Barron calls our “special forces” that detect and fight infections. That’s why it’s common for people who get measles to also get secondary infections after getting measles. Their bodies don’t have the defenses to fight additional infections. Read more about how people with measles can also deal with immunity amnesia.

Why are the current measles outbreaks so concerning: a snapshot of the numbers

Barron said the current measles outbreaks are extremely concerning.

Consider how measles causes severe medical challenges for those who get it, especially unvaccinated people:

• At least one in five unvaccinated people in the U.S. who gets measles will need to be hospitalized.
• As many as one of every 20 children with measles gets pneumonia, which is the most common cause of death from measles in young children.
• About one child of every 1,000 who gets the measles will develop what’s known as encephalitis or swelling of the brain. Encephalitis can lead to very frightening convulsions and can leave a child Deaf or with an intellectual disability.
• As many as three of every 1,000 children who become infected with measles will die from respiratory and neurologic complicatons.
• Measles may cause pregnant women who have not had vaccines for measles to give birth prematurely or to give birth to a low birth-weight baby.

Almost all of the people who have contracted measles so far this year have been unvaccinated or didn’t know their vaccine status, according to medical experts at the U.S. Centers for Disease Control and Prevention (CDC).

Here’s a snapshot of recent data about measles from the CDC and state health authorities:

• This year is proving to be tough for the spread of measles cases with hundreds already reported. There are far more than all of the cases in all of 2023, with 59 confirmed cases that year.
• Last year was also bad for measles. Altogether, there were 285 confirmed measles cases. They occurred in numerous states across the country.
• Measles hits children especially hard.
• Among those with confirmed measles cases in 2024, 42% were under age 5 and an additional 31% were ages 5 to 19.
• Of those with confirmed measles in 2024, 40% had to be hospitalized.
• Measles was officially eradicated in the U.S. in 2000, but after false information about measles vaccines took hold, vaccination rates dropped, and cases have climbed since then.
• The highest number of cases in recent years came in 2019 when U.S. health officials recorded a total of 1,274 confirmed measles cases across the U.S.

For people who have not been vaccinated, the likelihood of getting measles after an exposure is all but certain, Barron said.

That’s because the virus that causes measles has adapted to live a long time in the environment.

“When someone coughs, spits, or sneezes, the virus becomes airborne. Let’s say you are in line with me at the grocery store, and I have measles, and I am coughing or sneezing. The virus can hang out in the air for up to two hours after that and you can then breathe in the virus,” she said.

“If you are not protected by the vaccine, the measles virus then can infect you. CDC researchers estimate that nine of 10 people who lack protection to measles will develop measles infection if exposed to a close contact,’’ Barron said.

Her advice is very simple: “Get your vaccine. And if you’re concerned, talk to your provider. They have your best interests at heart. We went to school to learn how to take good care of people.”

Below, Dr. Barron and other medical experts answer your top questions about measles.

Is measles dangerous? Why do public health experts worry so much about measles?

According to CDC experts, measles is dangerous for the following reasons:

• The virus is highly contagious because it can live in the air for so long.
• A person who is sick and contagious with measles may not know they have it. People with measles can be contagious four days before the rash shows up and four days after it’s gone.
• Measles is so contagious that if one person has it, 9 out of 10 unvaccinated people who come in close contact with that person will also become infected.
• There is no treatment for measles. Patients can also get complications including ear infections and in more severe cases, pneumonia, seizures, inflammation of the brain, known as encephalitis and sometimes, death.
• Infants under three months of age cannot get vaccines to prevent measles and other illnesses. People with compromised immune systems, like those who have had transplants, also are at great risk for contracting diseases. Measles is extremely dangerous to vulnerable people including, babies, elderly and sick people.

What if you haven’t been vaccinated for measles? Are you likely to get it?

Yes. People who haven’t had the MMR vaccine (which stands for measles, mumps and rubella) are highly likely to get measles if they are exposed to someone with a confirmed case.

If an unvaccinated person who is exposed to the measles gets the MMR vaccine within 72 hours of an exposure to someone with measles, they might be able to prevent a full case of measles.

What happens if you get measles? How sick can you get?

Measles can cause scary complications, such as seizures, brain damage, ear infections, pneumonia and death.

Vaccination is highly effective against measles, and people who have previously been vaccinated with the MMR vaccine do not need to receive the vaccine again after exposure to measles. Coloradans can check their/their child’s vaccine status through an online database.

What are the signs and symptoms of measles?

The typical onset of symptoms typically takes place 7 to 14 days after exposure. But it may take up to 21 days for an infected person to get sick. A person with measles is contagious for four days before and four days after the rash appears.

Signs and symptoms of measles include:

• Fever, cough, runny nose, and red, watery eyes.
• The appearance of rash at the hairline, spreading downward over the body, usually beginning 2-4 days after other symptoms.

If exposed to the virus, how long does it take before signs and symptoms of measles appear?

After exposure to measles, it can take seven to 21 days for symptoms to appear.

What are the symptoms of measles?

Most people get a fever, cough, runny nose or red eyes at first. A rash that looks like red bumps appears on the chest and can appear on the arms and back. Characteristic spots can develop in the mouth. These spots often look like white spots in the back of the throat.

Is measles dangerous? Is it deadly?

Yes, measles is dangerous. According to the CDC, some people may suffer from severe complications, such as pneumonia (infection of the lungs) and encephalitis (swelling of the brain). They may need to be hospitalized and could die.

• As many as one out of every 20 children with measles gets pneumonia, the most common cause of death from measles in young children.
• About one child out of every 1,000 who gets measles will develop encephalitis (swelling of the brain) that can lead to convulsions and can leave the child deaf or with intellectual disability.
• For every 1,000 children who get measles, one or two will die from it.
• Measles may cause a pregnant woman to give birth prematurely or have a low-birth-weight baby.

What should you do if you or a family member might have measles?

Stay at home. Don’t go to work, school or daycare. Call your doctor or your care provider immediately.

Should patients have one or two MMR shots?

People who were born prior to 1957 are considered immune. If you were born between 1957 and 1989, you may have only had one shot. You should ask your doctor to either perform a blood test that determines whether your body is protected from the measles virus and whether you need another shot – a booster shot, or simply opt to have an MMR shot without the blood test. If you were born in 1989 or after, you probably have had two shots, but it’s a good idea to verify this.

What if a patient was born after 1989 and has had only one shot?

See your doctor. Your doctor can perform a blood test to check to see if you need to be protected from the measles virus and whether you need another shot. Or patients can simply opt to have an MMR shot without the blood test. There’s no danger in receiving an additional vaccination.

What if patients don’t know if they’ve had the MMR vaccine?

Your doctor can order a blood test to check to see if you need to be protected from measles.

How long does it take for the vaccination to go into effect so you’re protected from measles?

After a person gets the MMR vaccine, it takes about one week for the vaccine to become fully effective.

After receiving the first shot, how long do you need to wait to get the second shot?

Patients need to wait at least 28 days to get a second shot.

I thought we had nearly eradicated measles. Why is this dangerous illness coming back?

Like other vaccine-preventable diseases, illnesses like measles are on the rise because many parents are not vaccinating their children.

Dr. Heather Holmstrom, a family medicine expert at UCHealth Family Medicine Clinic in Boulder, urges all of her patients to get vaccinated.

“We eradicated these diseases, and now they’re coming back,” said Holmstrom, who is also an associate professor of family medicine at the University of Colorado School of Medicine.

Boulder is one of the areas in Colorado with poor vaccination rates. It’s also an area with a diverse and relatively wealthy population where many people travel around the world. Measles cases are on the rise around the globe. So, increased travel means it’s more likely that Coloradans can bring dangerous diseases home from abroad. Holmstrom spends considerable time educating parents about the importance of vaccines. She also encounters young adults who weren’t vaccinated as children.

“I encourage all young adults whose parents didn’t vaccinate them to get vaccinated,” Holmstrom said.

She often has to dispel common myths that have long since been disproven. There is no evidence that vaccines cause autism.

Holmstrom and her colleagues have to repeat that message over and over and constantly encourage parents to get their babies and children fully vaccinated.

“Routine childhood immunizations are really important for protecting every individual child as well as our community,” she said. “People ask me if I’ve vaccinated my own children, and I’m always really open with them. My own children have gotten every routine vaccine ever available.”

And, she tells them, “Yours should too.”

Who can I call in Colorado if I’m worried about measles? 

If you are worried that you may have been exposed to measles and you are experiencing symptoms, immediately notify your health care provider by telephone. Explain that you may have had a possible measles exposure and describe your symptoms. Call a medical provider before physically showing up to minimize the chance of exposure to other people. If you do not have a health care provider, call an urgent care center or emergency department. For additional information about measles, call the free helpline CO-HELP at 303-389-1687 (toll-free: 1-877-462-2911).

“Anyone who is experiencing symptoms of measles should stay home unless they need medical treatment,” said Dr. Rachel Herlihy, Colorado State Epidemiologist. “People with signs and symptoms of measles should also not go to child care facilities, school, work, or other public places to avoid exposing others to this very serious and highly contagious disease.”

Where can I get MMR vaccines?

The MMR vaccine is safe and effective at preventing measles (as well as mumps and rubella). Two doses of MMR are approximately 97% effective at preventing measles infection.
CDC experts recommend that children receive a first dose of MMR vaccine at 12 to 15 months of age and a second dose at 4 to 6 years of age. People who receive MMR vaccination according to the U.S. vaccination schedule are usually considered protected for life against measles.

The vaccine is widely available in Colorado for free or low cost. Call your medical provider, or speak to your doctor during a routine wellness exam for you or your children. The federal Vaccines for Children program provides vaccines at no cost for children from birth through 18 years who are uninsured, underinsured, on Medicaid or Medicaid eligible, and/or Alaskan Native/American Indian.