As an infectious disease specialist for nearly 26 years, Dr. Michelle Barron has never physically seen measles, and neither have a lot of other physicians of the 21st century.

The virus, most commonly identified by a flat red rash, fever, cough and white spots on the back of the throat, officially was eradicated in the United States in 2000, according to the Centers for Disease Control and Prevention.

“You should never see a case of measles if you’re doing things correctly,” said Barron, senior medical director of infection prevention and control for UCHealth, which locally operates the Memorial hospital system and ancillary clinics.

But declining vaccination rates nationwide have led to  isolated cases as well as outbreaks annually.

And this year’s outbreaks in Texas and New Mexico and cases in California, Alaska, Georgia, New York City, Kentucky, Rhode Island — and new cases in Florida and Pennsylvania as of Wednesday — have Barron and other medical professionals in Colorado on high alert.

“What’s going on in Texas is highly unusual — 159 cases is significant,” she said. “It’s spilled over into New Mexico, and that is not typical.”

Nationwide, the CDC has tracked 164 total cases of measles since Jan. 1, with the majority of patients being under age 20. Twenty percent of all patients have been hospitalized for complications, which include pneumonia and swelling of the brain.

In all of 2024, the U.S. had 285 cases, sending 40% of those infected to the hospital. There were 16 outbreaks last year, defined as three or more related cases, and one person died.

If the disease continues to spread as fast as it has this year — mostly among unvaccinated or under-vaccinated people — the situation could become problematic, said Barron, who also teaches about infectious diseases at the University of Colorado School of Medicine on the Anschutz Medical Campus in Aurora.

“We’ve had more than 50% of the cases for the entire year of 2024 occur in the last few months,” she said.

For all childhood vaccinations, Colorado’s statewide rates historically rank between 40^th and 50^th in the nation for low participation, Barron said.

There is no treatment for measles, she said, but patients can receive supportive care, such as assisted breathing or reduction of inflammation.

To gain widespread immunity, there needs to be a 95% vaccination rate, according to the CDC.

The immunization rate for the trio of measles, mumps and rubella (MMR) has fallen from 95.2% in 2019 to just 90.8% of children vaccinated by age 2, according to the CDC.

What’s concerning, Barron said, is that measles is one of the most contagious viruses.

“Measles is still far and above more infectious than the flu, COVID, RSV (another respiratory illness), even Ebola,” she said.

One person infected with measles has the potential to infect 12-18 more people, Barron said, compared with COVID-19, which has the potential of infecting six more people from one infected person.

Most cases of measles arise after international travel of a family or friend, Barron said, because the illness is increasing globally. But the virus can flit from one person to another in crowded public places, such as grocery stores and events.

“It can hang out in the air for two to three hours after somebody’s been there,” she said.

The best protection is to get vaccinated, Barron said, which she said is safe.

People who were born before 1956 are considered immune and don’t need to be vaccinated.

Children should get two doses of the MMR vaccine, starting with the first shot at age 12-15 months, and the second dose at 4-6 years.

Anyone who isn’t sure if they were vaccinated or think they only received one measles vaccine after its development in 1963 should consult with their primary care doctor. Anyone taking chemotherapy or whose immune system is compromised should also ask their health provider.

Contrary to information circulating on social media, vitamin A does not protect people from contracting measles, Barron said.

“We see no data that shows it has an impact and is not something we recommend,” she said.

State Epidemiologist Dr. Rachel Herlihy with the Colorado Department of Public Health and Environment issued a warning last week.

“We are seeing a concerning increase in measles cases across the country, including in states neighboring Colorado,” she said. “As Coloradans prepare for spring break and travel, it’s crucial to ensure you and your family are protected against this highly contagious and serious disease. The national surge of measles presents a risk to all unprotected people.”

The MMR vaccine is available for no or low-cost at doctor’s offices, community health centers, pharmacies, public health clinics and some schools. Two doses provide 97% protection, officials said.