Oregon measles outbreak grows to state's largest since 1991

Oregon's measles outbreak is now the largest reported outbreak in the state since 1991, according to data from the Oregon Health Authority.

The number of cases in the state since mid-June increased to 30 as of Sunday, surpassing the last outbreak in 2019 when 28 cases were reported.

Oregon's 2024 measles outbreak

This summer's outbreak is centered in Marion County, which has seen 20 cases, with additional cases in Clackamas and Multnomah counties. In 2019, the majority of cases were reported in Multnomah and Clackamas counties.

All cases have been unvaccinated individuals, and two have been hospitalized.

“Our measles outbreak continues, with two new cases identified since Friday," said Paul Cieslak, medical director for communicable diseases and immunizations at the Oregon Health Authority's Public Health Division. "The disease is among the most contagious known, and the only way we know to stop it is to maintain very high immunization rates — upwards of 95%. Two doses of vaccine provide lifelong protection for about 97% of recipients.”

Earlier in August, Cieslak said the outbreak was expected to continue.

"We don't have enough vaccinated people to stop the transmission, and so it goes on,” he said in Aug. 8 news briefing.

The outbreak marks the largest one reported in Oregon since measles was declared eliminated in the United States in 2000.

Oregon's measles outbreak is second largest in the country

Thirteen measles outbreaks have been reported across the country in 2024. As of Aug. 8, the Centers for Disease Control and Prevention reported 211 cases in 2024, compared to 58 cases in all of 2023.

The majority of cases this year — 87% — involved individuals who were either unvaccinated or had an unknown vaccination status.

Illinois is the only state this year to have reported more measles cases, at 67, than Oregon. Illinois declared its outbreak, which began in March, to be over in early June.

Measles outbreak blamed on falling vaccination rates

Public health officials cited an increase in vaccine exemptions for continued transmission of the highly contagious virus.

Since 2000, non-medical exemption rates for kindergartners have risen in Oregon from 1% to 8.8%, according to state data.

Health officials said 95% immunization is needed to reach herd immunity and stop the spread of measles.

In Marion County, 96% of kindergarten students were up to date with the MMR (measles, mumps, rubella) vaccine in 2023, exceeding the statewide rates of 94.4%.

Health officials said transmission is centered in pockets of unvaccinated individuals and parents should check their individual school's immunization reports. The data show, for example, 87% of students at Heritage Elementary School in Woodburn, 90% at Silverton High School and 51% at the Eugene Waldorf School are fully vaccinated.

As the 2024-25 school year approaches, officials warned that unvaccinated students who are exposed to measles may have to miss school for up to 21 days, the time it could take for them to develop the disease. That could be extended longer if cases continue to develop in the school.

Symptoms of the measles

Symptoms of measles include fever, cough, runny nose, red eyes and a rash that starts on the face and spreads throughout the body. The fever may spike to more than 104 F, according to the CDC. Unvaccinated pregnant people, infants younger than 1 years old and people with weakened immune systems are considered high risk.

People with measles can become contagious up to four days before developing symptoms and measles particles are known to be able to hang in the air for up to two hours.

“Measles is perhaps the most contagious disease that we know of,” Cieslak said in the Aug. 8 news briefing.

One to three of every 1,000 children who contract measles can die, and complications from the disease can lead to lifelong effects including hearing loss, deafness and intellectual disabilities, according to the CDC.

Isabel Funk covers breaking news and public safety for the Statesman Journal. Funk can be reached at ifunk@statesmanjournal.com or on X at @isabeldfunk

This article originally appeared on Salem Statesman Journal: Oregon measles outbreak grows to state's largest since 1991