Michele Marzola said she usually skips flu shots because they make her sick. That changed last month.

On Sept. 3, Kelsey Young, 20, died of swine flu, a week after delivering a healthy baby girl. She had become ill while pregnant. The news of Young's death, the first tied to swine flu in Franklin County and the second in Ohio involving a pregnant woman, prompted a wave of calls to area doctors' offices. Many were made by pregnant women. "I definitely have more concerns with swine flu," said Marzola, 34, of Westerville, who is due in November. "It just seems to be more severe, and more people seem to be dying from it."

Health experts and researchers have warned for weeks that as much as half the U.S. population could contract swine flu, also called H1N1, this flu season. That prediction, coupled with the annual toll that regular seasonal flu typically takes, means there will be a lot of sick people this winter.

Whether swine flu is more deadly than its seasonal cousin, which each year kills about 36,000 people in the United States, is unknown. The disease has not been as serious as officials first feared in April after the initial outbreak and several deaths were reported in Mexico.

Swine flu also defies easy predictions. "This virus is very different," said Columbus Health Commissioner Teresa C. Long.

Seasonal flu is deadliest among young children and adults older than 65. Swine-flu infection rates are 20 times higher in people 5 to 24 than they are in people older than 65, according to the Centers for Disease Control and Prevention.

Young was the third Ohioan to die of swine flu in recent months. The others were an 18-year-old Cuyahoga County woman who died shortly after giving birth, and a 46-year-old Butler County man. Both died in June.

Pregnancy makes women more susceptible to flu and to related complications, including bacterial lung infections such as pneumonia. "A pregnant woman's body is taking care of two beings," said Dr. Augustus Parker, an obstetrician and president of the Columbus Board of Health. "That stretches the immune system and makes it opportunistic for infections to attack the body."

Pregnant women with underlying health conditions, such as diabetes, can be even more susceptible, said Dr. Philip Samuels, an obstetrician at the Ohio State University Medical Center who specializes in high-risk pregnancies.

Seasonal-flu vaccines are available now. A vaccine for swine flu is being tested now and is expected by mid- to late October. The state got some more help from the federal government to prepare. The U.S. Department of Health and Human Services sent $29.8 million last month to help local health departments vaccinate residents. The department already had sent $17.5 million to help. "Local public health didn't have the capacity or infrastructure to run clinics for that large a number of people," said Bret Atkins, a spokesman with the Ohio Department of Health.

Long said expectant mothers and their immediate family members should definitely get both seasonal-flu and swine-flu shots once they are available. "We don't want people to panic," Long said. "We do want people to take action today to protect themselves."