Don't worry, Chicago. It’s only swine flu.

That was the message from city health officials at a press conference yesterday in advance of flu season.

“Don’t freak out, that’s the first thing I’d tell them,” said Department of Public Health Commissioner Terry Mason. “They should make sure they do things to mitigate the spread of disease."

Mason emphasized that Chicagoans need to practice healthy habits to prevent the spread of the common, seasonal flu and swine flu, also known as the H1N1 flu virus.

Starting Sept. 14, the city will offer seasonal flu shots at 45 one-day locations across Chicago. Those free vaccinations last until Oct. 14.

Officials are preparing for a second wave of flu season, and note that the virus is unpredictable. However, Mason said Chicago should receive an initial supply of 300,000 to 400,000 doses of the H1N1 vaccine when it is available, probably in October.  The vaccine will be distributed to hospitals and clinics, pharmacies and universities.

The swine flu scare, which has hospitalized 388 people in Illinois and killed 17 since April, is less virulent than officials feared, Mason said.

“The new strain of pandemic influenza that reached Chicago last April is still with us and still causing illness, although at a level greatly reduced from what we saw in the spring,” he said. “At the end of the day, this is the flu.”

About 37,000 people die each year in the United States of the common flu. According to the Centers for Disease Control and Prevention, 477 people have died of swine flu in the U.S.

As they did when swine flu first appeared in April, health officials are promoting healthy habits, like covering your mouth when you sneeze or cough, washing hands and staying home from work or school when you are sick.