Oregon health officials said Thursday that a measles outbreak in the Willamette Valley had spread to 25 residents – all of whom were unvaccinated.
The outbreak is unusual despite the disease’s high contagiousness, in part because it is easily controlled with vaccines. But vaccination rates have declined in recent years, health officials say, leading to repeated outbreaks.
The most recent outbreak occurred two months ago, when the state reported that an unvaccinated adult in Marion County had contracted the virus. The adult then transmitted the measles to an unvaccinated child in the same household.
According to Dr. Paul Cieslak, medical director of the Oregon Health Authority, there are 16 cases so far in Marion County, eight in Clackamas County and one in Multnomah County. Five of those cases are in adults over the age of 20, while the rest are under the age of 20, he said.
The outbreak is now the state’s largest since 2019, Cieslak said. This year, the state confirmed 28 cases. (Clark County, just across the Columbia River, experienced a “much larger outbreak” this year, he added.)
Measles is a highly contagious virus that spreads through the air and can linger in the body for up to two hours after a contagious person leaves the area, according to health officials. People are contagious for up to four days before a rash appears and up to four days afterward. This means a person may not yet know they have measles and may unknowingly spread the disease to others.
Symptoms include fever, cough, runny nose, and red eyes, followed by a rash that starts on the face and spreads to the rest of the body. These symptoms begin seven to 21 days after contact with the infection.
Officials said the spread of measles – which can be fatal – poses the greatest risk to people without a measles vaccine, pregnant women, infants under one year old and people with weakened immune systems.
Before a measles vaccine was available, an average of 400 to 500 people died from the virus each year in the United States, according to the Centers for Disease Control and Prevention. By 2000, after three decades of vaccination efforts, the virus was eradicated in the United States.
Cieslak said that before 2019, Oregon’s last measles outbreak was in the 1990s, which he attributes to the state’s “very high vaccination rates and very high population immunity.”
“Unfortunately, we are seeing a decline in the number of people getting vaccinated against measles,” he said.
Last school year, Oregon had the second-highest nonmedical exemption rate in the country, according to the Centers for Disease Control and Prevention. Officials say the measles, mumps, and rubella vaccine is highly effective against measles, but only if enough people are vaccinated.
Before 2000, about 1% of the state’s kindergarten students received a nonmedical exemption from school-based vaccinations, according to Cieslak. But that number has steadily increased, he said. Last school year, nearly 9% of the state’s kindergarten students had a nonmedical exemption.
“This threatens our herd immunity,” Cieslak said, referring to the prevalence of immunity to a disease in a large population. “Measles is perhaps the most contagious disease we know of. … It takes very high levels of immunity in the population to contain the transmission of this contagious disease.”
Dr. Sarah Present, Clackamas County health officer, said large numbers of people unvaccinated against measles could put their communities at risk.
“Measles is a serious disease. It’s not just a little rash. Complications are very common,” she said. “Not being able to go to school when you’re exposed to this disease can be a significant burden. Of course, the burden of contracting the disease yourself is even greater.”
Authorities urge anyone with measles symptoms to call a doctor or emergency center in advance to develop a plan to prevent others in the facility from becoming infected with the disease.
— Kristine de Leon covers retail, small business and data companies. Reach her at [email protected].
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