With the start of the new school year looming—and an ongoing measles outbreak in three counties: Multnomah, Clackamas and Marion counties—Oregon Health Authority (OHA) officials are urging parents and guardians to get their children vaccinated against the highly infectious virus.
A total of 25 confirmed cases of measles have been reported in Clackamas, Marion and Multnomah counties, all among unvaccinated individuals. Two people have been hospitalized, and there have been no deaths. 10 of the cases are nine and younger; 10 cases are ages 10 to 19; and five cases are 20 and older.
Paul Cieslak, M.D., OHA medical director for communicable diseases and immunizations, said state and county epidemiologists have seen several waves of measles cases since mid-June. It’s the largest measles outbreak the state has seen since 2019, when Oregon experienced 28 cases linked to a much larger outbreak in Clark County, WA.
“Before 2019, you have to go all the way back to the early 1990s to see case counts this high,” Cieslak said. “The reason is we maintained very high vaccination rates and very high population levels of immunity. Unfortunately, we’ve seen an erosion in the percentage of people who are getting vaccinated against measles.”
Since about 2000, an increasing number of parents have chosen nonmedical exemptions from state school vaccination requirements for their children. Before that year, only about one percent of kindergartners had vaccination exemptions; since then, the number has risen steadily, and during the 2023-24 school year, the exemption rate reached nearly nine percent.
“In Clackamas County, as in other Oregon counties, pockets of unvaccinated people raise risk of infection in communities where they live,” Clackamas County Health Officer Sarah Present, M.D. said. “That’s why the counties reach out to every case that’s been identified and try to determine exactly where they’ve been while infectious.”
Someone with measles can spread the virus up to four days before the tell-tale rash appears, and their symptoms may be mild during that time. As a result, the counties and OHA have been sharing information about specific locations that cases are known to have visited, so “we can let members of the public know they may have been exposed to measles,” Present said.
She noted that since measles is so contagious, an estimated 95 percent of a population needs to have received two doses of measles vaccine to be able to protect the most vulnerable members of the community via community or “herd” immunity.
Measles is a highly contagious, airborne disease. Measles starts with a fever, runny nose, cough, red eyes and sore throat, and is followed by a blotchy rash that starts on the face or at the hair line and then spreads all over the body. Approximately 30 percent of reported cases have one or more complications including pneumonia, ear infections or diarrhea. Rarely, the virus causes encephalitis (brain infection). Complications are more common in young children and adults.
Getting the MMR (measles, mumps and rubella) vaccine can also help families avoid the burden of having to isolate at home for several weeks if they are exposed to measles. According to state law, an unvaccinated person exposed to the virus must be excluded from school or child care during the period when they could become sick, which is usually for 21 days after exposure. And this exclusion can be extended if there are more measles cases.
“It’s really an important time to make sure students and their families are up to date on vaccinations as we go into the new school year,” Present explained.