DES MOINES -- The Iowa Department of Public Health on Friday reported three additional H1N1 influenza-related deaths in Iowa Friday, one of them in Woodbury County.

It is the second confirmed H1N1 death in Siouxland. The department reported Wednesday that a Monona County resident had died of the virus within the past few weeks.

Mike Krysl, Mercy Medical Center -- Sioux City spokesman, could not confirm Friday evening whether the death in Woodbury County was recent or if the health department had confirmed H1N1 flu as the cause of an earlier death at Mercy that was suspected of being caused by complications of the virus.

To date, Iowa has reported the confirmed H1N1 deaths of 13 adults and one child.

The most recent victims are identified as two adults in Polk County and one adult in Woodbury County; two of the three had known risk factors for complications, according to the state health department.

"Surveillance continues to show an increase in adult illness," said Dr. Patricia Quinlisk, the health department's medical director, "With H1N1 vaccine continuing to be allocated to states on a staggered basis, many adults are not yet in the priority group targeted for vaccination. However, in the coming weeks we expect more vaccine to become available in Iowa."

Quinlisk said the groups being vaccinated will continue to expand to include adults with medical conditions that put them at high risk for complications and death.

"Meanwhile," she said, "It's important for all Iowans to continue to take personal action to prevent the spread of illness."

Those steps include cleaning your hands frequently, covering your coughs and sneezes with a tissue or your sleeve and containing germs by staying home when ill.

Symptoms of H1N1 influenza are similar to seasonal influenza and include a fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. Some people with H1N1 flu also have diarrhea and vomiting.