A third confirmed measles case in Colorado, this time in Archuleta County, is prompting renewed public health worries amid signs of potential community spread.

The other two cases — a deli worker in Pueblo and an infant in Denver — do not appear to be related to the case in Pagosa Springs, said Dr. Rachel Herlihy, state epidemiologist and deputy chief medical officer at the Colorado Department of Public Health and Environment.

This suggests that measles might be spreading in what’s called “community transmission” because the cases, geographically, are spread out, Herlihy said. Pueblo is roughly 115 miles south of Denver, while Pagosa Springs is about 275 miles southwest of the Mile High City.

“We do know that typically when we see these sporadic measles cases, they’re related to people traveling outside of Colorado,” Herlihy told The Denver Gazette.

According to health officials, the infected adult in Archuleta County was at the Wolf Creek Ski Area and Resort March 28th through the 30th. The state health department publicly reported the case on Tuesday. Typically, patients are contagious four days before and after presenting with a rash.

Health officials are urging those who may have been at the ski resort at that time to monitor their symptoms and ensure they are up-to-date on their vaccinations.

The cases in Pueblo and Denver involved international travel to Chihuahua, Mexico, which is experiencing an ongoing outbreak.

Measles is a highly contagious but preventable respiratory illness that is transmitted through direct contact with infected droplets or airborne when a person breathes, coughs or sneezes.

Symptoms typically emerge within two weeks of exposure with a spotty red rash — the telltale sign of a measles infection.

In rare cases, measles can cause swelling of the brain and death.

Measles was considered eradicated in 2000, with officials crediting a highly effective vaccination campaign.

Over the past decade, Colorado has had just six measles cases. Most years, the state doesn’t report any cases.

But vaccination rates across the state can vary widely.

The City of Pueblo, for example, has an 84% vaccination rate against measles for children younger than 5 and 92% in the county. The rate for school-age children is 95% in the city and county.

As of April 3, there were 607 reported measles cases nationwide. More than 500 of those cases originated in Texas, starting in a religious community in the panhandle.

Statewide the vaccination rate last school year for school-age children was 93.7% — just shy of the 95% epidemiologists say is needed to prevent measles from spreading and provide what’s called “herd immunity.” Simply put, herd immunity is what occurs when enough people in a community are immune to a disease, either through prior infection or vaccination.

Before a vaccine was developed in the 1960s, an estimated 48,000 Americans were hospitalized with measles and 500 died each year.

Measles cases in the U.S. peaked in 1990 with 27,808 infections, according to the Centers for Disease Control and Prevention (CDC). The last major case spike was in 2019 when there were 1,274 measles cases over the course of the year.

CDC officials maintain that the risk for widespread measles in the U.S. remains low. While a booster is not yet recommended, the CDC is encouraging all Americans be up-to-date on their vaccinations.

Those with a measles, mumps, and rubella (MMR) vaccine or who were born before 1957 — when the disease was so widespread everyone exposed to the virus developed natural immunity — are generally considered immune.

The bulk of the cases nationally have been among either unvaccinated patients or those who have an unknown status, according to the CDC.