This story has been updated to reflect that the Teton Valley, Idaho, case is connected to the Colter Bay outbreak. The case is also counted as one of the five cases in Teton County, Wyoming. — Ed.
A vaccinated adult tested positive for measles this week in Teton Valley. It’s the second case in eastern Idaho this year and is one of the five cases from the ongoing outbreak in Teton County, Wyoming.
The individual likely contracted the highly contagious disease after close contact with a known case, according to a press release from Eastern Idaho Public Health. Teton County, Wyoming, Public Health Director Travis Riddell confirmed the case involved a Teton County, Idaho, resident who was exposed to one of the cases in Colter Bay in Grand Teton National Park.
Teton County, Wyoming, county commissioners declared a local emergency earlier this week.
The public may have been exposed to the individual at Broulim’s grocery store in Driggs, Idaho, on July 6 from 5:15 p.m. to 6 p.m. Public health officials said the disease can linger in the air and infect others for an additional two hours.
Only two to three percent of people vaccinated with the full series of the measles, mumps and rubella (MMR) vaccine still contract the virus, according to Jordan McAdam, health strategy manager for Eastern Idaho Public Health said in the press release.
Still, McAdams said, vaccination is the “best defense” against measles for both children and adults and helps limit its spread within the community.
Public health officials recommend checking personal vaccination records and seeking the vaccine if lacking. When in doubt, it is not harmful for adults to get another dose, according to Teton County Public Health Director Dr. Travis Riddell.
Experts recommend getting the two-dose vaccination if born after 1957, since those born before are considered immune after likely being infected as children.
Measles symptoms include fever and a rash of tiny red spots that spreads from the head. Additional symptoms could include small white spots on the inside of the cheek, a cough with a runny nose and red eyes.
Measles was declared eliminated in 2000 and kept that status for almost 20 years due to successful vaccine programs, according to the U.S. Centers for Disease Control and Prevention. So far in 2026, there have been more than 2,000 reported cases across the U.S., according to a measles tracker from Johns Hopkins.
