The Jefferson County, Pennsylvania coroner says he’s confirmed an “active measles infection” in a 40-year-old Pennsylvania woman who died Saturday morning. She also had ongoing lung problems, including asthma and chronic obstructive pulmonary disease, or COPD, the coroner’s office said. “She did have a pretty extensive medical history,” said Jason Stiver, chief deputy coroner and public relations officer for Jefferson County. “She was on oxygen 24/7.” Monday evening, the coroner’s office said that a nasal swab taken from the woman upon her death tested positive for measles. “The positive test result supports the determination that the decedent was suffering from an active measles infection at the time of death,” according to a press release from the coroner’s office. The woman, Stiver said, was pronounced dead in her home just before 8 a.m. Saturday. She hadn’t been vaccinated against measles. The measles-mumps-rubella vaccine is 97% effective in preventing measles infection, experts say. Joe Raedle / Getty ImagesThe woman had symptoms of measles, including a fever and the telltale rash, Stiver said, and was living in a house with other people who had the same measles symptoms. She also had direct contact with another family member in a different household who had been “laboratory tested and confirmed” to have measles, Stiver said.This is the third death in the state amid a surging outbreak of the virus. Two infants, according to the Lancaster County coroner, died last month of measles-related complications. One baby died at birth after his mother, also infected with measles, went into labor a month early. As of Monday, 693 cases had been confirmed in the state this year, 99 of them in the last week alone. The latest situation is a prime example of how the virus can be deadly in people with underlying health problems. Once measles begins circulating in the body, it can attack multiple organs, including the lungs and the heart. In very rare cases, an infection can result in a dangerous and almost always fatal brain condition called subacute sclerosing panencephalitis, or SSPE, a decade later. It also suggests that Pennsylvania’s outbreak is far worse than official case counts suggest. Historically, measles infections cause 1 to 2 deaths per 1,000 cases. Three deaths in a short period of time indicate the state may have as many as 3,000 cases. Many people, experts say, don’t get tested.News of the latest death comes amid an ongoing political back-and-forth between Pennsylvania and federal health officials. The Centers for Disease Control and Prevention hasn’t acknowledged the measles deaths in the state. A spokesperson from the state Health Department told NBC News the agency informed the CDC on Monday morning that it was investigating the death in Jefferson County, which a CDC spokesperson confirmed. The CDC’s director, Dr. Erica Schwartz, said in a statement that, unlike other states with outbreaks, Pennsylvania hadn’t requested the CDC’s assistance in its ongoing measles outbreak. The Pennsylvania Health Department “maintains a strong working relationship with the professional staff at the CDC, which includes regular meetings, and we will continue to evaluate any additional CDC support as this outbreak continues,” the spokesperson wrote in an email. The U.S. is experiencing its largest measles outbreak since 1991, with 3,294 confirmed cases this year, according to the CDC.In addition to the people who have died in Pennsylvania, three others died of complications related to measles in 2025. One was an adult in New Mexico. Two young girls died in Texas in its massive outbreak, which ultimately spread to at least 762 people.