Amid spikes nationally, Oregon measles outbreak grows to state's largest in years
Oregon's measles outbreak is now the largest in the state in over three decades, mirroring a trend of rising measles cases across the U.S. this year.
Nearly one-third of measles cases since the COVID-19 pandemic occurred in the past three months, according to the Centers for Disease Control and Prevention.
The number of cases in Oregon's outbreak first tracked in mid-June grew to 31 as of Tuesday, surpassing the last outbreak in the state, in 2019, when 28 cases were reported.
Health experts attribute the reappearance of the disease to the falling rate of children getting measles, mumps and rubella (MMR) vaccinations. They have noted that outbreaks are mostly confined to pockets of the population where young people have not been vaccinated.
"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%," said Paul Cieslak, medical director for communicable diseases and immunizations at the Oregon Health Authority's Public Health Division. "Two doses of vaccine provide lifelong protection for about 97% of recipients.”
Oregon 2024 measles outbreak
All of those infected during the outbreak were people who were unvaccinated, according to the Oregon Health Authority. Two people were hospitalized, officials said. The outbreak is the largest reported in Oregon since measles was declared eliminated in the United States in 2000.
Oregon's measles outbreak is also the second-largest in the country, among 13 outbreaks reported in 2024. As of Tuesday, the CDC reported 236 U.S. cases in just over eight months this year, compared with 58 cases in all of 2023.
The majority of cases across the U.S. this year – 87% – involved people who had not been vaccinated or whose vaccination status was unknown.
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Earlier this year, outbreaks occurred in an elementary school in Florida and a migrant shelter in Chicago. Illinois and Minnesota are the only states to have reported more measles cases than Oregon. Illinois had 67 and Minnesota had 41 to Oregon's 31.
Illinois declared its outbreak, which began in March, to be over in early June. However, health officials in Oregon expect the state's outbreak will continue.
"We don't have enough vaccinated people to stop the transmission, and so it goes on,” Cieslak said at a news briefing Aug. 8.
Outbreaks blamed on falling vaccination rates
Oregon public health officials noted the state has seen an increase in families seeking vaccine exemptions, which makes it easier for the highly contagious airborne virus to continue being passed from person to person.
Since 2000, non-medical exemption rates for kindergartners have risen from 1% to 8.8%, according to state data. Health officials said 95% immunization is necessary for a population to reach herd immunity and stop the spread of measles. The nationwide rate among American kindergartners is about 93%.
Health experts say transmission is centered in pockets of unvaccinated people. They suggest parents check their children's school's immunization reports.
As the kids return to school, officials warned that unvaccinated students 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 they get sick.
Symptoms of the measles
Measles, a highly contagious virus, spreads easily and can be serious or fatal for children who are not vaccinated.
According to the CDC, the virus is so contagious that if one person has measles, up to 90% of people close to that person who are not immune will also become infected.
The virus lives in the nose and throat mucus of an infected person and can spread to others through coughing and sneezing, or contaminated surfaces. People with measles can become contagious up to four days before they develop symptoms. Measles particles can hang in the air for up to two hours after a sick person has sneezed or coughed.
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“Measles is perhaps the most contagious disease that we know of,” Cieslak said.
The telltale symptom of measles is a rash that starts on the face and spreads throughout the body. Other symptoms include fever, cough, runny nose and red eyes. The fever may spike to more than 104 degrees, according to the CDC. Unvaccinated pregnant people, infants younger than 1 and people with weakened immune systems are considered at high risk if exposed to the virus.
One to 3 of every 1,000 children who contract measles can die. Complications from the disease can cause lifelong harm, including hearing loss, deafness and intellectual disabilities, according to the CDC.
Contributing: Eduardo Cuevas and Emily DeLetter
Adrianna Rodriguez can be reached at adrodriguez@usatoday.com Isabel Funk can be reached at ifunk@statesmanjournal.com or on X, formerly Twitter at @isabeldfunk