A 23-year-old Sonoma County man died Wednesday from complications of the H1N1 flu, a strain similar to the virus that caused the swine flu pandemic in 2009, county health officials said.

Also, two H1N1-related deaths in Marin County and one in Mendocino County have been reported this week as public health officials urge the public to get vaccinated against the flu.

The Sonoma County resident who died is among nine local residents who have been diagnosed with severe cases of the flu, said Karen Holbrook, the county's interim public health officer. A severe flu case is one where a patient either is admitted to an intensive care unit or dies.

"Our deepest sympathies go out to the family," Holbrook said. "While the vast majority of cases of flu have mild or moderate illness. Sadly this tragic death reminds all of us that influenza is a very serious illness."

Holbrook would not release information about the patient out of respect for the privacy of the individual's family. She would only say that the individual was previously healthy. Other sources identified person as male.

The death occurs at a time when reports of H1N1 illness and death are on the rise in counties across the state, as well as in other states. The highest rates of flu illness have been documented in the South and Southeast.

"Overall surveillance says it's been H1N1," Holbrook said. "That's what's circulating this season."

Mendocino County health officials reported Thursday that an adult there died on Dec. 30 from chronic conditions complicated by H1N1 flu. Mendocino health officials also reported that eight patients have been admitted to local hospitals with confirmed H1N1 flu.

In Marin County, two people have died from complications of influenza, said Dr. Matt Willis, the county's public health officer.

Willis said the first case involved a 63-year-old man who died in late December. The man had contracted influenza A, of which H1N1 is a subtype. Willis said the determination of the precise virus type is still pending.

Willis said the man had significant previous chronic health conditions and had not been vaccinated.

In the second case, an otherwise healthy 48-year-old woman died last week after coming down with Influenza A. She also had not been vaccinated, he said.

Holbrook said that of the eight severe cases of flu in Sonoma County -#8212; those requiring admittance to intensive care facilities -#8212; the majority were not vaccinated.

Willis said that in Marin County there have been 84 confirmed Influenza A cases out 470 respiratory specimens tested. Of those 84, 16 have been determined to be H1N1 and three were H3N2, which was the dominant strain last year.

"This particular strain of H1N1 was first introduced globally in 2009/2010," Willis said, adding that it's been present in every flu strain since then. "Pretty much exactly the same strain that was present in 2009 and 2010."

The virus that caused the 1918 pandemic was a strain of the "H1N1 family," Willis said. The current strain has raised concerns among health officials because "it seems to be affecting people in all age ranges and not just the more vulnerable populations that we typically see affected by influenza."

Influenza typically hits the elderly and very young or those with compromised immune systems. But the current strain of H1N1 also affects young adults, though it causes severe illness in people of all age groups.

Holbrook and Willis urged people to get vaccinated, pointing out that there should be adequate supply of vaccine.

On Thursday, Alex Roh of Santa Rosa brought his two sons -#8212; Justin, 13, and James, 11 -#8212; to Annadel Medical Group offices in Santa Rosa to get vaccinated against the flu. Roh himself got vaccinated after hearing more about its effectiveness.

"I feel better now," he said. "I think I did the right thing."

Katy Hillenmeyer, a spokeswoman for the St. Joseph Health System in Sonoma County, which is affiliated with Annadel Medical Group and runs Memorial Hospital, said there have been two hospital patients admitted since the beginning of the year with confirmed cases of H1N1 flu.

She said that in December a patient at Memorial Hospital tested positive for H1N1 but did not require hospital admission. At Petaluma Valley Hospital, there have been no<NO1><NO> H1N1 admissions to the hospital <NO1><NO>in December or January. She said that in December <NO1><NO>four patients who tested positive for H1N1 were seen at the Petaluma hospital on an outpatient basis.

<NO1><NO>Willis said it takes about two weeks for a person to build immunity once the vaccine is received. He said that peak activity for the flu is in early February.

Holbrook said that the current vaccine being given for the flu will combat the current strain of H1N1. The county said getting the annual <NO1><NO>flu vaccine is a crucial step in protecting individuals and the community against the spread of the virus.