Currently, Oregon’s measles outbreak is the most significant the state has seen in over 30 years, coinciding with a national rise in measles cases this year.

According to the Centers for Disease Control and Prevention (CDC), nearly one-third of measles cases since the COVID-19 pandemic have occurred in just the past three months.

As of Tuesday, the number of measles cases in Oregon, which began tracking in mid-June, has risen to 31, exceeding the previous outbreak in 2019 that reported 28 cases.

Health officials point to declining vaccination rates for measles, mumps, and rubella (MMR) as a primary factor in the return of this illness. They have observed that outbreaks predominantly occur in communities where young people have not received vaccinations.

“Measles is one of the most contagious diseases known to mankind, and the key to preventing its spread is ensuring extremely high immunization coverage—over 95%,” explained Paul Cieslak, the Oregon Health Authority’s medical director for communicable diseases and immunization programs. “Receiving two doses of the vaccine offers lifetime protection for approximately 97% of individuals.”

Overview of Oregon’s 2024 measles outbreak

According to the Oregon Health Authority, all individuals infected during this outbreak were unvaccinated. Two people have required hospitalization due to the disease. This outbreak represents the largest recorded in Oregon since measles was declared eliminated in the U.S. in 2000.

Moreover, Oregon’s outbreak is now the second largest in the nation, among 13 outbreaks reported in 2024. As of Tuesday, the CDC noted a total of 236 measles cases across the U.S. in just over eight months this year, contrasting with only 58 cases throughout all of 2023.

This year, about 87% of measles cases in the U.S. involved individuals who were either unvaccinated or whose vaccination status was unknown.

Earlier this year, there were outbreaks in an elementary school in Florida and a migrant shelter in Chicago. Illinois has reported more measles cases than Oregon this year, with Illinois tallying 67 cases compared to Oregon’s 31.

Illinois declared the end of its outbreak, which began in March, in early June. However, health officials in Oregon predict that the state’s outbreak is likely to persist.

“We lack sufficient vaccination rates to halt transmission, so it continues,” Cieslak noted during an August 8 news conference.

Impact of declining vaccination rates on outbreaks

Public health authorities in Oregon have observed a rise in families applying for vaccine exemptions, facilitating the spread of this highly infectious airborne virus.

Since 2000, the rate of non-medical exemptions among kindergartners has surged from 1% to 8.8%, per state data. Officials state a 95% immunization rate is essential for achieving herd immunity and stopping measles transmission. The national rate for American kindergartners is approximately 93%.

Health professionals emphasize that transmission occurs mainly within groups of unvaccinated individuals. They recommend that parents review their children’s schools’ immunization records.

As students return to educational settings, officials have warned that unvaccinated individuals exposed to measles may need to stay home for up to 21 days, the period it could take for them to develop symptoms. This period could extend further if they become ill.

Recognizing measles symptoms

Measles is a very contagious virus that can lead to serious or fatal consequences for unvaccinated children.

The CDC indicates that the virus is so infectious that when one individual contracts measles, up to 90% of those nearby who are not immune may also get infected.

The virus can spread through the mucus from the nose and throat of an infected person and can be transmitted through respiratory droplets or by touching contaminated surfaces. People with measles can be contagious for up to four days prior to showing symptoms. Measles virus particles can linger in the air for up to two hours following a cough or sneeze from an infected person.

Cieslak remarked, “Measles may be one of the most contagious diseases that exists.”

The characteristic symptom of measles is a rash that begins on the face and then spreads across the body, accompanied by other symptoms such as fever, cough, runny nose, and red eyes. The fever can rise above 104 degrees Fahrenheit, according to the CDC. Unvaccinated pregnant women, infants younger than one year, and individuals with compromised immune systems are at high risk when exposed to the virus.

According to the CDC, one to three out of every 1,000 children who catch measles may die. Additionally, complications arising from the disease can lead to permanent issues, such as hearing loss, deafness, and intellectual disabilities.

Contributors: Eduardo Cuevas and Emily DeLetter, YSL News. Isabel Funk can be contacted at ifunk@statesmanjournal.com or on X, previously Twitter at @isabeldfunk