Hundreds of people who were at Centennial Middle School in Southeast Portland this month may have been exposed to measles, according to state and county public health officials.

The Oregon Health Authority has published a detailed list of times and dates in April when a person who was infectious was at the school.

Multnomah County health officials are working with the school district to directly contact people who were exposed and are at risk, and state officials are encouraging anyone who is concerned they may have been exposed to contact their doctor right away.

Public health experts generally consider measles to be the most contagious respiratory virus known. Bustling, crowded schools can be hubs for outbreaks.

Centennial Middle has 849 students enrolled this year.

In an interview on Tuesday, Multnomah County’s deputy public health officer, Dr. Theresa Everson, told OPB that she’s optimistic her department will be successful working with the school to stop further transmission of the virus.

About 95% of the school’s students are vaccinated against measles, and the overwhelming majority have received both recommended doses of the shot.

For measles, a vaccination rate of at least 95% is the threshold that reduces the risk of a full-blown outbreak.

“In general, in Oregon, most people are still vaccinating,” Everson said. “There are people who have questions or hesitations, but, on the whole, we are still doing a pretty good job vaccinating, and this school is no different.”

According to Everson, the county and OHA are now following a standard process defined by state law to help ensure that exposures at the school don’t turn into a new chain of transmission, and to contain the impact of the virus.

That starts with working with the Centennial School District to identify people who were exposed.

The definition of exposure is a person who shared airspace with somebody who was infectious with the measles.

The virus can linger in the air for up to two hours after a person has coughed or sneezed, so exposure can last for up to two hours after an infected person has left the room.

Everson says the health department is contacting anyone present at the school while measles was in the air.

“We are talking about the teachers and administrators and volunteers and the people who work in the cafeteria and the people who do environmental services,” she said.

One unique aspect of school exposures is that public health officials have a head start in identifying who is most at risk of getting sick.

Every February, on what’s known as “Exclusion Day,” each school in Oregon requires families to provide current vaccination records, or exemption records, for every student, per state law.

Now that a measles exposure has been reported at Centennial, public health officials use those records to assess which students are not vaccinated.

Measles is highly contagious, infecting 9 out of 10 unvaccinated people who are exposed to it, according to the Centers for Disease Control and Prevention. Its early symptoms — a runny nose and itchy eyes — are non-specific and easily confused with other conditions.

To reduce the chances of it spreading, unvaccinated students will need to stay home for 21 days after their last date of exposure to the virus.

That group could include students with health conditions like cancer that make it impossible to get vaccinated, as well as those whose families decline vaccination or don’t have regular health care.

Figuring out which adults are susceptible to the virus and need to isolate is more challenging because schools generally don’t have vaccination records for staff on file.

The county public health department is notifying those adults directly if they need to discuss their risk of exposure, susceptibility to the virus, and the need to stay home.

District officials said students and staff who are vaccinated with at least one dose of the measles vaccine, or who have documented immunity to measles, can continue to attend school or work.

Alternative ways of demonstrating immunity include lab records showing the presence of measles antibodies, records showing a previous measles diagnosis, or birth before 1957.

Students and staff without immunity will need to stay home for 21 days following their exposure and may be excluded through May 1. The district is planning to support students with access to course materials and content and regular communication with families, according to district spokesperson Christine Andregg.

The school district and the health department sent detailed instructions to all families on Monday.

Centennial Middle is the second school in the region to weather a measles exposure. In January, during a measles outbreak in Clark County, a person at Ridgefield High School was contagious with measles for 3 days.

More than 1,200 students attend that school, but the vast majority of them were vaccinated.

In the end, more than 21 days passed with no new transmission of the virus, and the county was able to declare the outbreak over.

Elka Sundwall, a public health nurse on the Infectious Diseases team in Clark County, said vaccination was one element of turning that outbreak around. The other was everyone in the community, vaccinated and unvaccinated, working together to stop the virus in its tracks.

“I can’t speak highly enough of the community response,” Sundwall said. “The school, sick individuals, everyone was doing everything they could to make sure it didn’t go any further, and I think that made all the difference.”

The measles vaccine is highly effective. One dose provides about 93% percent lifetime protection against infection, while two doses provide about 97% lifetime protection, even if you’ve been exposed.

The Centennial School District did not immediately respond to a request for comment about how they are supporting students and families.

Meanwhile, the state health authority announced another measles exposure on Tuesday afternoon, at a health care facility in Oregon City.

Public health officials say people with symptoms of measles should, whenever possible, call ahead to their health care provider or urgent care to create an entry plan to avoid exposing others in waiting rooms.

Staying home when you’re sick and finding out your measles vaccination status are other steps you can take to reduce the risk of exposing other people.

News Source : https://www.opb.org/article/2026/04/14/measles-has-reached-a-portland-school-heres-why-health-officials-think-they-can-stop-it/