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A woman living in rural northwestern Washington has died from measles, state health officials said Thursday. It’s the first U.S. death in a dozen years.

No one suspected the woman had measles. Tests taken at her autopsy showed she had the virus, which can be deadly. The woman, who was not identified, died of pneumonia, a common consequence of measles, sometime this spring, authorities said.

“The woman was most likely exposed to measles at a local medical facility during a recent outbreak in Clallam County,” the state health department said in a statement.

“She was there at the same time as a person who later developed a rash and was contagious for measles," it said. "The woman had several other health conditions and was on medications that contributed to a suppressed immune system. She didn't have some of the common symptoms of measles such as a rash, so the infection wasn't discovered until after her death.”

“She was there at the same time as a person who later developed a rash and was contagious for measles."

The county had a small outbreak of measles earlier this year but officials said at the time it was not directly linked to the Disneyland outbreak, in which 147 people were infected.

Officials said the woman’s death shows the value of vaccines.

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“This tragic situation illustrates the importance of immunizing as many people as possible to provide a high level of community protection against measles,” the health department statement said.

"We know that measles can be deadly," said Dr. Anne Schuchat, who directs the respiratory diseases branch at the the Centers for Disease Control and Prevention.

"We think that one in 2,000 … will die from it even with great medical care. We are very sad about this because we think in general of measles as a preventable disease." And measles can make people very sick. Schuchat said one in four U.S. cases end up in the hospital, and one in 1,000 develop a serious and life-threatening brain inflammation known as encephalitis.

Health officials say they urge universal vaccination for even the sickest people, and small babies too young to be vaccinated, can be protected.

“People with compromised immune systems often cannot be vaccinated against measles," Washington's health department said.

"Even when vaccinated, they may not have a good immune response when exposed to disease; they may be especially vulnerable to disease outbreaks. Public health officials recommend that everyone who is eligible for the measles, mumps, and rubella (MMR) vaccine get vaccinated so they can help protect themselves, their families, and the vulnerable people in their community.”

The Disneyland outbreak stirred up debate over mandatory vaccinations. California had liberal laws allowing people to decline to vaccinate their kids for personal reasons. But after the CDC said pockets of unvaccinated people helped spread measles, legislators worked to change the law.

“People with compromised immune systems often cannot be vaccinated against measles."

Governor Jerry Brown just signed a tough new law Tuesday. It only allows schoolchildren to skip vaccines with a doctor's note.

“Measles is highly contagious even before the rash starts, and is easily spread when an infected person breathes, coughs, or sneezes. If you're not protected, you can get measles just by walking into a room where someone with the disease has been in the past couple of hours,” the Washington statement said.

“The last confirmed measles death in the United States was reported in 2003.”

Measles is rare in the U.S. The last bad epidemic was in 1989-1991, when 55,000 cases were reported and 123 children died. Vaccination efforts have been stepped up since then.

"Until about 2010 we were seeing 30 to 50 cases a year," Schuchat said. But numbers have been much higher since then, with 644 cases last year.

"When we look over the last five years, a pattern emerges. We see many cases in people who have not been vaccinated not because the system didn’t reach them but because they or their parents did not want to be vaccinated," Schuchat said.