DENVER — Spring break travel is dovetailing with an increase in measles cases in Colorado and nationwide.
As of Thursday, Colorado had reported 10 cases of the highly transmissible virus. Nationally, the number of confirmed measles infections has already topped more than 1,300. That already represents 60% of all measles cases the U.S. reported in all of 2025.
How concerned should you be if you are traveling right now?
Denver7 anchor Shannon Ogden spoke with Dr. David Merriam, assistant professor of biology at Metropolitan State University of Denver. His areas of expertise include microbiology, understanding vaccine safety, hesitancy, and how well vaccines work.
Dr. Merriam said if you are vaccinated against measles, which 88% of us are, then you really needn't worry. If you are unvaccinated, however, Dr. Merriam says it's not necessarily the measles itself you should be most concerned about. It is secondary infections from a phenomenon called "immune amnesia" caused by measles.
"It's essentially that your immune system has memory of everything you've ever encountered in the past. Suddenly, now, forget that. So if you've had COVID in the past, if you get measles, your body no longer remembers having COVID and it can't fight off COVID as well," said Dr. Merriam.
According to the University of Colorado Anschutz Department of Medicine, immune amnesia can be a long-lasting side effect of getting measles. With no treatments for it, individuals may face an increased risk of getting sick for at least two years, research shows.
The U.S. Centers for Disease Control and Prevention says the best protection against measles is the measles, mumps, and rubella (MMR) vaccine, which is 97% effective against infection. The MMR vaccine provides long-lasting protection against all strains of measles.
- Denver7 has been closely following confirmed measles cases in Colorado amid a multi-state outbreak in the U.S. that began last year. Explore the map by clicking here or check it out below to see where cases have popped up in 2026:
For those who choose to remain unvaccinated, Dr. Merriam advises them to take advantage of the Colorado Department of Public Health and Environment's measles outbreak tracker and simply avoid going out in public in places where measles cases are reported.
"If there's a region where you are seeing measles coming out, like if you're in Broomfield, I might avoid going out into public right now," said Merriam.
According to Dr. Merriam, approximately 92% of recent measles cases were in individuals who were either unvaccinated or had an unknown vaccination status and if you are unvaccinated, there is an approximately a 90% chance of infection if exposed.
The CDC says about one out of five people who get measles will be hospitalized, and one to three out of 1,000 people with measles will die.
Colorado has reported cases of the virus in Adams (5), Arapahoe (1), Broomfield (3), and Weld (1) counties. On average, the state sees between zero and two cases each year. Last year, Colorado reported 36 measles cases amid a multi-state outbreak of the virus in the U.S.
