The other states were Mississippi and Hawaii, the Centers for Disease Control and Prevention in Atlanta said.
Dr. Ron Chapman, director of the California Department of Public Health and state health officer, said while health officials were seeing an increase in flu activity in the Golden State it is not an unexpected increase, nor is it too late to get vaccinated against the flu.
"California is seeing an accelerated increase in flu activity over the past few weeks," Chapman said in a statement. "You can help prevent further spread of the flu by getting a flu shot."
Influenza activity varies from year to year and is unpredictable. California generally sees an increase in cases in late December or early January, and it often peaks in February or March. Influenza activity in California is beginning to show a steady increase, Chapman said.
"The best defense against the flu is getting vaccinated. This year's vaccine is an excellent match against this year's influenza strains," Chapman said. "There is no shortage of vaccine in California and it is not too late to get vaccinated. Our flu season may not peak for several more weeks, so I encourage everyone to get vaccinated to protect not only themselves, but those with whom they come into contact."
Those at highest risk -- the elderly, pregnant women, infants or those with other health conditions -- who show flu symptoms should contact their physician immediately in order to get the most effective treatment.