Eighty unvaccinated students and staff at Broomfield middle and high schools are not allowed to attend class in the wake of a measles outbreak, state health officials confirmed Tuesday.

The majority of the exclusions are students, but they also include several staff members, Hope Shuler, a spokesperson with the Colorado Department of Public Health and Environment, said in an email to The Denver Gazette.

The exclusion period is 21 days from the last known exposure.

But if measles infections continue to occur in a school, unvaccinated students could be excluded beyond the initial period.

“By keeping susceptible individuals away from potential exposure, we stop the virus from finding new hosts and prevent a localized, containable incident from becoming a community-wide crisis like we’re seeing in large measles outbreaks in South Carolina, Utah/Arizona, and Florida,” Shuler said.

“Similar school exclusions have occurred throughout the country in the past year, including in South Carolina, Texas, Minnesota, New Mexico, and Oklahoma.”

Under state statute, public health officials have the authority to exclude unvaccinated students — including those with exemptions — from school to stop an outbreak of a vaccine-preventable disease.

With three cases linked to a case from Broomfield High School, state health officials declared a measles outbreak last week.

Randy Barber, a Boulder Valley spokesperson, declined to say what academic supports are being provided for the students.

To the consternation of health care officials, measles was declared eradicated in 2000.

Measles is a highly contagious and preventative respiratory illness transmitted through direct contact with infected droplets or airborne when an individual breathes, coughs, or sneezes.

Symptoms typically emerge within two weeks of exposure. The telltale sign of a measles infection is a spotty red rash. In rare cases, measles can cause swelling of the brain and death.

A highly effective vaccination campaign is credited with eradicating measles. Before the vaccine, an estimated 48,000 Americans were hospitalized with measles and 500 died each year.

With the outbreak in Broomfield schools, state officials are investigating 3,700 known contacts linked to the seven measles cases in this outbreak, Shuler said.

“The investigation is ongoing, but based on illness timing, most of the cases in the outbreak had an exposure to an unidentified case that was infectious in Broomfield in early February and was not detected,” Shuler said. “None of the cases we have identified so far appear to be the first or index case in this outbreak.”

The public is encouraged to watch for symptoms up to 21 days after exposure.

The eight measles cases reported so far this year exceed the total confirmed in Colorado since 2017.

About 93.3% of students in Colorado were vaccinated for measles, mumps and rubella last school year, state vaccination records show. To be protective, 95% or more of students should be vaccinated against measles.

Colorado recorded 36 measles cases last year — more than the previous decade combined — with roughly 1 in 4 associated with an out-of-state traveler who flew while infectious, according to the Colorado Department of Public Health and Environment.

That’s what keeps Dr. Michelle Barron, senior medical director of infection prevention and control for UCHealth, up at night.

“Colorado’s big risk right now is it being imported from somebody visiting,” Barron has said.

The positive cases in Colorado come as the United States has seen an unprecedented rise in the number of cases.

As of March 5, there were 1,281 confirmed measles cases in 31 states, according to the Centers for Disease Control and Prevention.