ATLANTA (AP) -- The first study of U.S. health care workers with swine flu found that many didn't do enough to protect themselves against the virus.

Researchers focused on 13 nurses and other health care workers who were likely infected at work in the early days of the U.S. outbreak. They found that only half always wore gloves, and even fewer routinely wore other protection around patients who might have the virus.

In late April -- just as U.S. cases were first mounting -- the U.S. Centers for Disease Control and Prevention said health care workers should wear gloves, gowns, eye protection and respirator masks when dealing with patients suspected of having swine flu. The CDC also advised sick workers to stay home.

To date, about 80 health care workers have been confirmed with swine flu. The study examined the 26 cases of infected workers with detailed information as of mid-May.

The study's numbers are too small to generalize about what's going on in clinics and hospitals. But they suggest that at least some health care workers aren't doing enough to identify and isolate patients with swine flu and take precautions when treating them, said Dr. Michael Bell, a CDC official focused on infection control in health care settings.

"I think we've been lucky that this first wave has not been of the lethality that some people feared," Bell said, at a news conference Thursday.

But CDC officials say many health care workers will need to improve how they deal with the flu, especially if -- as some fear -- the virus mutates into a deadlier form.

The study is being published this week in a CDC publication, Morbidity and Mortality Weekly Report.

The 80 cases of health care workers is out of the nearly 18,000 confirmed and probable U.S. cases reported as of last Friday. Those numbers suggest health care workers are underrepresented in the case counts, CDC officials said.

About 1,600 people have been hospitalized and at least 44 died, according to CDC numbers. Many of the victims were younger adults, children and people with other illnesses. About 40 percent of those hospitalized have been people with asthma, diabetes, heart disease and other medical conditions, said Dr. Daniel Jernigan, a CDC flu expert.

Widespread cases in 17 states -- particularly in the Northeast -- suggest swine flu will continue through July and August and into the fall and winter, he said.

In some earlier flu pandemics, the new virus essentially elbowed out other flu strains. It's likely that swine flu will circulate along with seasonal flu bugs in the fall, Jernigan said.

Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.