Pennsylvania officials are reporting a fourth measles-associated death. An 18-year-old from Mifflin County died from a severe neurological complication of the virus. None of the four who died were vaccinated. The U.S. is experiencing its worst measles year since 1991, with seven deaths in two years. Pennsylvania's outbreak includes nearly 700 illnesses across 38 counties. These are the first measles-associated deaths in the state in 35 years. Health officials emphasize the importance of the MMR vaccine to prevent outbreaks. International health officials will meet in November to assess the U.S. and Mexico's measles-free status.

Bacteria that cause Legionnaires' disease have been found in a Yankee Stadium cooling tower in New York City. Health officials say it's one of 10 towers that tested positive for Legionella bacteria amid 10 recent cases of the disease in the Bronx, including one death. The city Health Department said Sunday that more tests are being conducted to determine if the bacteria are live. Only live bacteria can cause Legionnaires' disease. The Yankees say none of the current cases has been linked to the stadium and the stadium cooling tower was cleaned Sunday. Legionnaires' disease is a form of pneumonia and is treatable, but can be fatal.