A second Sonoma County resident has died of complications from the H1N1 flu virus, according to the county health department.

The 54-year-old resident, whose name and gender was not released Monday, died Sunday and had "underlying medical conditions that put the individual at risk for severe illness," said Karen Holbrook, the county's interim public health officer.

"Influenza can be a serious illness and we need to take steps to protect ourselves and loved ones," Holbrook said.

There have been 11 "severe cases" of influenza illness in Sonoma County, Holbrook said. A severe case is where a patient has either died or has been admitted to an intensive care unit from flu illness.

Last week, Matthew "Matty" Walker, 23, of Santa Rosa died after he contracted the H1N1 flu virus. In that case, Walker's family has expressed concerns that his illness was not recognized in time to possibly save his life.

Also, two H1N1-related deaths have been reported in Marin County and one in Mendocino County.

Across the country, health care professionals are reporting accelerated flu activity over the past few weeks, Holbrook said. Most of that activity involves the H1N1 virus.

She said there have already been more severe cases of flu illness in Sonoma County this year compared to last year. During the 2009/2010 flu season, there were 20 severe cases for patients under 65, compared to 11 thus far, she said.

In 2009, the H1N1 outbreak came earlier in the year, and in two stages, compared to other flu seasons. This flu season, though it is dominated by the H1N1 virus, is following a more conventional schedule and is expected to peak in February.

Holbrook urged county residents to get a flu vaccine, which she called the best defense against the flu.

"There are no shortages of vaccine," she said.

She said residents should take the usual flu season precautions, including covering your mouth when you cough, avoid spreading germs by not touching eyes, nose or mouth, and if you become ill with flu-like symptoms see a medical provider immediately.

Symptoms include fever, cough, sore throat, runny or stuffy nose, body aches, headaches and fatigue.

For more information about the flu, visit <a href="http://www.sonoma-county.org/health/topics/influenza.asp" target="_blank">www.sonoma-county.org/health/topics/influenza.asp</a>