Last year’s measles outbreak was dubbed the worst in the U.S. in 14 years, with 288 cases of the potentially deadly infection popping up in 18 states, but no one died. Similarly, the more recent measles cases at Disneyland and in Las Vegas raised awareness of the disease’s return but left everyone involved alive. Now health officials in Washington state are saying the pneumonia death of a woman there is believed the be the first measles-related fatality in the U.S. in a dozen years.

According to the Washington State Dept. of Health, the woman had visited a medical facility in Clallam County in the northwest region of the state this spring at the same time as another person who was later found to be contagious for measles. She is the sixth person in the county to be diagnosed with measles this year, and the 11th in the entire state.

The victim’s measles, which didn’t present common symptoms like rash, went untreated and the disease was not known to be involved her death until it was discovered at autopsy. The DOH says she had other health conditions and had been on medications that contributed to a suppressed immune system.

“This tragic situation illustrates the importance of immunizing as many people as possible to provide a high level of community protection against measles,” reads the statement from the DOH, noting that those with compromised immune systems are often unable to be vaccinated against the disease, and even if they can “they may not have a good immune response when exposed to disease; they may be especially vulnerable to disease outbreaks.”

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