Colorado Public Radio originally published this story on June 4, 2025.
Updated on Wednesday, June 4, 2025, at 2:41 p.m.
Colorado public health officials said Wednesday they've identified a new measles case in Colorado, this time in a Denver County resident who tested positive for it, according to a press release from the Colorado Department of Public Health and Environment and the Denver Department of Public Health and Environment. It's the latest case, now more than half a dozen, linked to a passenger on Turkish Airlines flight 201. It arrived at Denver International Airport from Istanbul on Tuesday, May 13. The individual is recovering at home.
Seven Colorado cases are associated with the out-of-state traveler who flew while infectious. Four were passengers on the May 13 flight and three were at Denver International Airport during the exposure period on May 14.
Original story below:
A little more than two months ago, on March 31, Colorado public health officials recorded the state’s first case of measles in 2025. In the last few days, the state hit double digits. That figure, 11 as of Wednesday, June 3, according to the state’s website, is more than every case from the last decade combined.
All the cases, except for one in Archuleta County, have ties to international travel, and the state’s chief medical officer told CPR this week that he’s seen no sign of community transmission in the state. But that may only be a matter of time. The cases have varied widely; some have been in children, others in adults, most have been in unvaccinated people, though some of the cases are in vaccinated adults.
The latest cases of measles are tied to passengers who recently flew to Denver from Istanbul.
The state health department and El Paso County Public Health said Sunday they'd confirmed measles in three adult El Paso County residents. They said two were unvaccinated and are recovering at home.
Public health officials said they're notifying the public of additional areas for potential measles exposures as a result of these confirmed cases. The adults are unrelated, but they were at Denver International Airport around the same time on Wednesday, May 14.
A third Colorado passenger on Turkish Airlines flight 201 that arrived in Denver on May 13 has been confirmed positive for measles. The vaccinated adult from Arapahoe County is recovering at home. No public exposures have been identified because of this case.
In the U.S., nearly 1,100 cases have been reported in 2025, with the majority of states recording cases, according to the Centers for Disease Control and Prevention.
What should Coloradans know about measles, amid the latest cases, including those involving air travel.
For answers, CPR Health Reporter John Daley turned to Dr. Michelle Barron, Senior Medical Director of UCHealth Infection Prevention and Control.
This interview has been edited for length and clarity
Daley: Colorado has now topped double digits for measles cases in 2025. That’s more in just five months than the total recorded in the prior decade. What do you make of that?
Barron: I think it's a reflection, obviously, of the amount of measles that we're seeing across the country as well as in other countries. And it's unfortunate in that this is a vaccine-preventable disease, but I think because we haven't seen cases in so many years, I think people sort of fell into this comfort zone that they didn't need to get vaccinated anymore. And that's clearly reflected in the decline in vaccination of children.
Daley: We now have several cases connected to an international flight, a flight from Istanbul to Denver. Is this a reminder of how contagious measles is — that an infected person on a flight might infect many people?
Barron: People don't really appreciate how infectious measles is. It's considered our most infectious disease in terms of transmission and being on that plane. With measles, if you were on the plane or if you were even in DIA and happened to be in line at the same spot or on the train, you could have potentially gotten exposed and ended up infected. So yeah, I think again, it's sort of hard to imagine until you see it in real life.
Daley: Also, we have confirmed cases involving people who were at Denver International Airport at the same time. Can you explain how transmission might have happened in this situation?
Barron: So when people get measles, you can get infection into the lungs. We think about the rash, we think about the red eyes, but you certainly have it everywhere, and it's in what we call your oropharyngeal cavity. So in your nose and in your throat. And so if you're coughing, if you're talking, if you happen to be somebody who was singing, the virus gets suspended into the air and it can hang out in the air for up to two hours. And so, depending on how close you are, how the air handlers work, everybody's breathing this air. So if I happen to cough and you're sitting next to me and you're potentially vulnerable to measles and you breathe it in.
But the sad thing is, what if I was sitting at a bench, I got on my plane, and then you come along an hour later, it could still be hanging out in that airspace, which is why this is so contagious and so easy for people to get it is that you don't even have to be next to them in real time. It could be up to two hours where it's hanging out and your air handling systems certainly help distribute new air and put new things into circulation. But most of the time, it's probably not going to eliminate it all rapidly. Like it's still going to be there for a while at best. Maybe you could clear it in 45 minutes with really good air handling, but that's still a long time if you think about how many people move in and move out from these spaces.
Daley: Most of the Colorado cases are in unvaccinated people, but some involved vaccinated adults. From what I understand, that’s not necessarily surprising. Can you explain how that happens?
Barron: So nothing unfortunately, is a 100 percent vaccination. So if you got one MMR, it's about 91 percent effective. If you get two MMRs, it's 97 percent protective. So that means 3 percent of people with two vaccinations still potentially could get measles. So if you look across the U.S. right now, the number of cases, which I think is almost 1,100 cases, if you look at the breakthrough, it's about 3 percent. So somebody will argue, “Well then, why get the vaccine if you're still going to get infected?” I would say if you knew there was a 97 percent chance that you were going to win the lottery, you would buy a ticket. You would not focus on the 3 percent and worry about, like, “Oh, but there's a 3 percent chance.” If you look at the normal odds, buying a lottery ticket is so much worse than the chance that you're going to get measles if you're fully vaccinated.
Daley: According to the health department, more Coloradans of all ages are now getting the MMR vaccine to protect against measles? What would it take for Colorado to reach the threshold where it could have broad community protection?
Barron: So again, this virus or infection is a little different in terms of the threshold of protection. And unfortunately, measles is one that requires a very high level of protection for you to have the sort of herd immunity that we talk about sometimes. So we need 97 percent of Coloradans to be vaccinated for this to not continue to potentially spread. And that doesn't mean that we wouldn't periodically still see a couple of cases, but we wouldn't have the continued spread. And if you look at Texas and New Mexico and why that spread so quickly and so widely, it was because the population that was so under-vaccinated that they were vulnerable, and it just kept perpetuating … I think this has gotten a lot of people sort of thinking about it.
Note: Colorado's current MMR vaccination rate for kindergarteners is 88 percent, according to CDPHE. For all students K-12, the rate is 93.3 percent. Both are below the 95 percent threshold needed to limit or prevent the spread of measles in a community. Some individual schools' rates are much lower even than those statewide rates, putting them at risk for an outbreak.
Daley: One potential outcome of this would be that maybe we do get up to that level where we could see better protection? Also, we have not seen, as far as I know, any community spread yet. All of the cases have been tied to international travel, that could change any day now, right?
Barron: That's obviously the worry that we have right now is that, is this the tipping point, right? We know about the ones we know about so far, but are there additional cases of people that were at DIA that just haven't come in to get evaluated, are there contacts amongst these people that potentially, again, are now going to manifest with infections? That's the other thing. There's a lag time, so it's not an immediate thing. It could be up to two weeks after your initial exposure, before you develop symptoms. So I think we're very hopeful, obviously, that people are taking this seriously, making sure they're checking their vaccination status and getting vaccinated appropriately. But I think we're still going to probably see more cases. I think it's hopeful to think that we won't, but I think we probably will still see some addition again, hopefully it will not be to the extent that we saw in Texas, though.
Daley: A lot of people are traveling, with summer here. What’s your advice in terms of avoiding measles?
Barron: The CDC actually just put an alert, a travel alert. It's level one, which means they're not telling you not to travel or do things, but it's an alert that suggests that if you're going to be traveling abroad, to make sure you're up to date on MMR and make sure you have your vaccines. If your children are too young to get the vaccine, or maybe they're in that window where they've got one, but they're not eligible for the second quite yet, based on age to talk to your providers about what are the risk benefits? Should I be doing something different? Obviously, look, there is great information on where the outbreaks are occurring across the world, and so when you look at, and it may not be as exotic as you think, Canada currently is having major outbreaks. They had 1,200 cases in Canada last week as of last week, and the area, there's different provinces.
Daley: One of the Colorado cases involved a child who was hospitalized. So that really spotlights the seriousness.
Barron: It does. And I think that is something, again, it doesn't happen often, but when it happens, it can be, and mostly in children, but it can certainly occur in adults as well. You can get pneumonia, you can get swelling of your brain, you can actually get pretty sick from this. And obviously, there's been deaths associated with measles. It's not common. This is not meant to meet, really just to tell you that this can be a serious disease. And we're very fortunate that we live in a world where we have a vaccine that can prevent this. Because if you look back to the 1950s and sixties, the number of cases were in the 500,000. And you can imagine, because so many people were impacted by this, the death rates were higher. It's because so many more people were impacted by this.
Daley: Anything else to add?
Barron: Vaccinations work, and they're safe. I want one more plug: MMR is safe. There is nothing that suggests that there are any issues associated with this vaccine other than typical side effects that you can see with vaccines. Talk to your provider. Please do not get your information off the internet and assume it's correct because there's so much stuff out there that is incorrect that you really want to talk to the person who takes care of you, who knows your health and can give you the honest answers about whether or not this is the right thing for you. But the link to autism was debunked a long time ago, and there are no alternatives to a vaccine for preventing measles. Vitamin A does not work. In fact, it could potentially cause toxicities and land you in the hospital. Cod oil does not work. Nothing else works other than this vaccine. It's been tried and it didn't work.
Editor's note: This story was updated to clarify Colorado cases of measles. Ten involve international travel and one case is unlinked to another case and the individual had not traveled outside of the state.
