Alameda County Public Health Department spokeswoman Sherri Willis said the man who died Wednesday suffered from chronic health problems.
On Tuesday, county health officials announced the death of another middle-aged man who had tested positive for the /*H1N1*/ virus, and who also suffered from chronic health problems.
Last week, health officials in Contra Costa County announced that a 9-year-old girl in that county with H1N1 died May 29.
The World Health Organization today declared the H1N1 outbreak a pandemic.
"Countries should prepare to see cases, or the further spread of cases, in the near future. Countries where outbreaks appear to have peaked should prepare for a second wave of infection," WHO Director-General Margaret Chan said in a statement.
As of Wednesday, 74 countries have reported 27,737 cases of H1N1 infection and 141 deaths, according to WHO statistics.