People who attended the first evening of the Canby Rodeo could have been exposed to measles, according to the Oregon Health Authority. The exposure took place between 7:30 p.m. and 11 p.m. on Tuesday, August 18
Measles is a highly contagious respiratory virus that spreads when an infected person coughs or sneezes
Flagging vaccination rates among children have allowed the virus to regain a foothold in the U.S., with more reported measles cases in the last two years than in the previous 25 years combined
The Canby Rodeo draws about 25,000 attendees from across the state for barrel racing, bull riding and other events the third week in August. It takes place at the Clackamas County fairgrounds in an open-air stadium with a covered grandstand
It’s rare for public health officials to issue exposure notices for outdoor events. Most viruses, including measles, are rapidly inactivated by sunlight, and good airflow reduces the risk of respiratory virus transmission
A number of factors led public health officials to issue the broad public exposure notice, said Sarah Present, health officer for Clackamas County
People sit very close together at the rodeo, and health officials didn’t have ticket-level data to help identify who might have been sitting near the person who was infectious
“Because it’s so crowded, there’s so much milling around into and out of bathroom areas, we really can’t pinpoint more specific times or enclosed spaces,” Present said. “There are enough unknowns and enough potentially vulnerable people.”
Present said the exposure notice is also intended to alert doctors who suspect they might be seeing a case of measles to ask their patients if they attended the rodeo
Measles has an incubation period of 7 to 21 days, meaning that if susceptible people did get infected, they could be showing symptoms soon
Measles is easily preventable with a vaccine, but there is no antiviral treatment for it. An infection can lead to hospitalization and lifelong complications, particularly for children under 5, pregnant people and others with weakened immune systems
A recent review of studies of airborne transmission of the virus by researchers at Johns Hopkins Bloomberg School of Public Health found that there is a major gap in evidence to guide contact tracing for measles in outdoor public spaces
The researchers did not identify any studies that assessed virus transmissibility in outdoor air
Two doses of the measles vaccine provide 97% protection against measles, meaning that 97 out of 100 vaccinated people will not get sick if they are exposed to the virus. Two doses usually provide lifelong protection, according to the Centers for Disease Control and Prevention
OHA has reported 50 cases of measles so far this year. Three cases were in people who had been vaccinated. The remaining 47 were in unvaccinated people or people whose vaccination status isn’t known
