By Stephanie Stahl

PHILADELPHIA (CBS) — Delaware has announced its third flu-related death of the year and Pennsylvania is quickly catching up with the rest of the country.

The Keystone State is reporting more than 25,000 confirmed flu cases and 47 deaths. Most of the flu cases were reported during the past three weeks.

And those facing the highest risk are the elderly.

Ronald Lebrane got his first flu shot ever this year. The 69-year-old with heart disease had two heart attacks in the past.

“I always say, ‘Naw, I don’t want a flu shot’ and something hit me and I decided to do it,” he recalled.

A new study suggests his decision could help keep his heart healthy.

The research published in the New England Journal of Medicine says the chances of a heart attack increases six-fold during the first seven days after getting the flu.

“During their flu episode, their body goes through a lot of changes,” Dr. Ravi Dave, a cardiologist at UCLA Health, explained. “It goes through increased inflammation, increased stress; their blood vessels tend to go into spasms, their blood gets a little more thicker, all of these things can lead to complications of heart attack and a stroke.”

Researchers looked at 20,000 adults in Canada and found the risk may be higher for older adults, patients with influenza B infections and patients who never had a heart attack.

Doctors say the findings magnify the importance of getting vaccinated and taking precautions like washing your hands and staying home at least 24 hours after fever subsides.

“This season in particular has been devastating for patients with heart disease, diabetes, asthma because when they get the flu, their risk for having respiratory problems, including death, have been very high,” Dr. Dave said.

Lebrane says he plans to get vaccinated every year from now.

“People are dying out there and I don’t even have a tickle in my throat,” he said.

Federal health officials say the flu continues to surge nationally, and this flu season is now the most severe since 2009. They add that it’s still not too late to get a flu shot.

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