Eastern Idaho Public Health on Thursday reported a second case of measles in an unvaccinated child in Bonneville County, following a young international traveler contracting the disease last week.

The health agency confirmed the local child who contracted measles this week represents the first case of the disease in an Eastern Idaho resident since 1991. EIPH is continuing to monitor known contacts for potential infection.

The measles virus was detected in wastewater in Coeur d’Alene from a sample taken July 29, prompting state health officials to encourage Idaho medical providers to be vigilant for the disease. Within a week, an unvaccinated child from a foreign country visiting Bonneville County contracted measles. The child was isolated during the contagious period, evaluated by a health care provider and was not hospitalized, according to EIPH.

The new measles case in Eastern Idaho is epidemiologically linked — the local child experienced symptoms after being in contact with the young international traveler earlier in August. According to EIPH, the virus carriers are self-isolating and the agency anticipates that household contacts have the potential to become infected.

The U.S. Centers for Disease Control and Prevention reported that the 2025 national case count for measles reached 1,356 as of Aug. 5. This compares to 285 measles cases nationwide in 2024 and 59 cases in 2023.

Measles is a highly contagious virus that spreads easily through the air and settles on surfaces. Up to 90% of those in contact with an infected person may be at risk.

Vaccines have historically been used to prevent measles infection. According to the World Health Organization, vaccination resulted in an 80% decrease in measles deaths worldwide between 2000 and 2007.

Measles symptoms typically appear 7-14 days after exposure and can result in a high fever, distinctive rash, coughing, runny nose, inflamed eyes and white spots inside the mouth. Fewer than 10% of those with measles experience complications including diarrhea, ear infections and pneumonia.

There is currently no antiviral treatment for measles.

EIPH is urging the public to check vaccination records through their primary care provider. According to the agency, individuals who have received the measles, mumps and rubella (MMR) vaccine or have had a confirmed case of measles in the past are considered immune to the virus.

Anyone born before 1957 is also immune, according to EIPH. The MMR vaccine is 97% effective at preventing measles after receiving two doses.

”If you suspect that you or someone in your household has measles, it is important to stay home to prevent the spread of measles,” a press release from EIPH said. “For those who wish to test or receive medical care for symptoms, it is essential to call your medical provider before visiting to prevent further spread of infection. For questions about measles symptoms or receiving the MMR vaccine, contact your health care provider.”{/div}{/div}