Colorado health officials have declared a measles outbreak in Broomfield after confirming multiple cases tied to kids who attended a middle and high school in the suburb northwest of Denver.

“It’s a perfect storm. The worst-case scenario is having a measles outbreak in a school. Look at how quickly the number of cases has grown,” said Dr. Michelle Barron, UCHealth’s senior medical director for infection control and prevention.

As of March 19, Colorado health officials have confirmed measles infections in 10 people in the Broomfield area, including students who attended Broomfield High School and Broomfield Heights Middle School. Another young person traveled through Denver International Airport in February with a confirmed case of measles. And an adult in Weld County has tested positive for measles. The person in Weld County traveled to an area of the U.S. where measles is spreading, and health officials do not think that case is related to the Broomfield outbreak.

Barron and other medical experts expect the number of measles cases tied to the Broomfield outbreak to continue rising. That’s because measles is so contagious. It spreads more easily than diseases including COVID-19, flu, polio and Ebola.

Along with being extremely infectious, measles is also very dangerous.

“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 Anschutz School of Medicine.

Why does measles spread so quickly in schools? 

Barron expects the number of measles cases in Colorado to continue rising quickly since that’s exactly what’s happening in other measles outbreaks around the U.S.

So far this year, health experts at the U.S. Centers for Disease Control and Prevention (CDC) have identified 1,362 confirmed cases of measles.

A measles outbreak in South Carolina has spread to nearly 1,000 people so far.

And an outbreak at a Catholic college in Florida has infected scores of students.

“Look at how quickly the measles outbreak escalated in Florida. The students were on a college campus. They hang out together. They eat meals together,” Barron said.

Just like college students, teens roam around and gather with friends. That’s why Colorado health officials have highlighted multiple counties and multiple restaurants, stores and other public locations where unvaccinated people could have been exposed to the highly infectious virus.

“When you’re in enclosed spaces for long periods of time, which schools generally are, it’s going to spread,” Barron said. “Everybody’s in classrooms, hallways, bathrooms. Anybody who is breathing the air where an infected person has been could get exposed.”

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

That’s because the virus that causes measles has adapted to survive for long periods in the air.

“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.”

Where did infected students travel in the Broomfield area?

The list of locations where infected teens traveled within the Broomfield area is long, precisely because young people love to socialize with one another, Barron said.

Here are the locations where health officials say people who are unvaccinated for measles could have been exposed to the dangerous virus. For exact dates and details about possible measles exposures in Colorado, view measles outbreak information on the Colorado Department of Public Health and Environment’s website.

Arvada:

Bout Time Pub & Grill

Broomfield:

• Advanced Urgent Care
• Broomfield Heights Middle School
• Broomfield Community Center
• Broomfield High School
• Chick-fil-A
• Children’s Hospital of Colorado, North Campus
• Chippers Bowling Alley
• Rey Soopers
• UCHealth Broomfield Hospital Emergency Department

Frederick

CommonSpirit Emergency & Urgent Care Indian Peaks

Lafayette

Efrain’s Mexican Restaurant

Louisville

CU Medicine Family Medicine Clinic

Westminster

• Arby’s
• Chipotle
• Coldstone Creamery
• Kaiser Permanente Hidden Lake Medical Offices
• Kaiser Permanente Westminster Clinic
• PetSmart Walnut Creek

Along with Denver International Airport, where else did the person who was infected with measles travel within the Denver area?

Colorado health officials have identified the following locations where an unvaccinated young person with measles traveled in the Denver area in February 2026:

• Aeropuerto Internacional de Denver
• St. Mary’s Catholic Church, Littleton
• Woodside Baptist Church, Denver

Where did the person in Weld County travel?

The person who tested positive in Weld County was in these locations:

• UCHealth Medical Center of the Rockies Emergency Department, Loveland.
• UCHealth Medical Center of the Rockies outpatient pharmacy, Loveland.

How are Colorado health officials fighting the Broomfield measles outbreak?

Health officials are requiring any unvaccinated students and staff members from Broomfield High School and Broomfield Heights Middle School to stay home for 21 days. Barron said quarantines can help fight measles outbreaks.

“Typically, people will develop symptoms about seven to 14 days after an exposure. But it could be up to 21 days. Keeping individuals at home helps minimize who gets exposed,” Barron said.

“You are most infectious four days before a rash starts and four days afterward,” she added.

What should you do if you think you might have been exposed to measles?

If you think you might have been exposed to measles, it’s vital to stay home so you can avoid spreading the illness.

Barron and state health officials are asking parents and individuals who think they might have measles to call ahead before visiting a doctor’s office, urgent care clinic or hospital ER.

And be sure to tell health care providers that you might have been exposed to measles.

“We really want to minimize the number of other people who are exposed. Even if it turns out that you’re sick with something different, we want to make sure we’re taking precautions. If you think you have measles, you should call ahead. And we would ask that you wear a mask because that helps minimize exposure to others,” Barron said. “Be sure to tell people up front that you’re concerned that you might have measles. We’ll put you in a different room and will expedite the process of having you see a provider.”

Symptoms of measles include fever, cough, runny nose, red eyes, and a characteristic rash that usually starts on the face and spreads.

What about people who are fully vaccinated for measles? Are they safe to go to school or activities?

Barron said people who are fully vaccinated should be fine attending school and visiting public places.

“If they’re immunized, they’re safe,” Barron said. “There’s no reason for them (anyone who is fully vaccinated) not to continue with their activities,” she said.

Measles infections have been surging in Colorado and across the U.S.

Measles infections have been surging in 2026 after reaching their highest levels in decades across Colorado and the U.S. in 2025.

Nationally, health officials confirmed at least 2,280 measles cases in 2025, the highest number since the early 1990s. Colorado health experts reported 36 measles cases in 2025, a huge jump from previous years, when Colorado doctors rarely saw patients with measles and state officials logged two cases at most per year.

The disease is especially harmful to young children. It can cause very serious illnesses and fatalities. And in 2025, measles killed three people in the U.S.

“Measles is not, and never was, a benign illness,” Barron said.

Barron is keeping a very close eye on the Colorado measles cases and outbreaks elsewhere in the U.S. and around the world since the disease spreads so easily and can be so dangerous.

Barron is urging Coloradans to check their vaccination status and get vaccinated right away if they don’t know their vaccination history or haven’t been fully vaccinated against 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 in tamping down measles outbreaks is that people are infectious for up to four days before they feel sick or develop 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.

In addition to causing the initial illness, measles is more destructive than other infectious diseases, such as the 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.

That’s because measles causes severe medical challenges for those who get it, especially unvaccinated people. Here are some medical complications that can strike people who get measles:

• At least one in five unvaccinated people in the U.S. who gets measles will need to be hospitalized.
• As many as one in every 20 children who becomes infected with measles will also get pneumonia, which is the most common cause of death from measles in young children.
• About one child of every1,000 who gets measles will develop 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 complications.
• Measles may cause pregnant women who have not been vaccinated to give birth prematurely or to give birth to a low birth-weight baby.

Among people who have gotten sick with measles this year, 94% have been unvaccinated, nearly identical to 2025, when 93% of those with confirmed measles cases also had not received their measles vaccines, according to experts at the 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, with hundreds of cases already reported across the U.S.
• South Carolina is having the worst measles outbreak this year, but multiple other states also are seeing high numbers of measles cases. They include Florida, California, Washington, Utah, Arizona and North Carolina.
• Measles hits children especially hard.
• Among people with confirmed measles cases in 2025, 26% were under age 5, and an additional 44% were ages 5 to 19.
• Of those with confirmed measles in 2025, 11% 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. It’s likely that the U.S. now will lose its status as a place where measles has been eradicated.
• The highest number of cases in recent years prior to 2025 was in 2019, when U.S. health officials reported 1,274 confirmed measles cases nationwide. The U.S. already has surpassed the 2019 high water mark just two months into 2026.
• The number of measles cases in the U.S. in 2025 was the highest since 1991, when health officials logged 9,643 cases. That’s when doctors began giving patients two doses of the measles vaccine.

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 appears and four days after it clears.
• 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 six 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, the 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 begins 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 experts, 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 repeatedly 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 the 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.