Pennsylvania reported its first swine flu-related death tonight, a 55-year-old woman from Berks County.

The woman, who was not identified, had a "significant underlying health condition," said Stacy Kriedeman, spokeswoman for the state Department of Health.

Berks County had 75 laboratory-confirmed cases of H1N1 through today, by far the biggest chunk of the 269 statewide, but the high number is at least partly due to aggressive testing by infectious-disease investigators who are studying an outbreak at an elementary school in the town of Womelsdorf. None of the schoolchildren has been hospitalized, and Kriedeman said it was unclear whether the woman had a connection to that community.

Eighteen people have died from H1N1 complications nationwide, most of them with underlying medical conditions. No deaths have been reported in New Jersey, which has 148 confirmed cases, or Delaware, with 139. "The death of this 55-year-old woman is a sad reminder of the complications that can result from A/H1N1 virus," Pennsylvania Secretary of Health Everette James said in a statement tonight.

No other information about the woman was available.

Five schools have been closed this week in York and Lancaster Counties, although neither has large numbers of confirmed cases of H1N1. The Conrad Weiser West Elementary School in Berks County reopened May 21 after a one-week closure.

Four people have been hospitalized to date statewide, Kriedeman said, although the vast majority of cases are mild.