The Los Angeles Times says the liver-damaging illness has infected at least 568 people since last November, chiefly in San Diego, Santa Cruz and Los Angeles counties.
Most cases and all 17 deaths occurred in San Diego County. The Times says experts believe the highly contagious disease was spread by transients there to homeless populations around the state.
Although vaccination programs and other measures are underway, experts say it's unlikely the worst is over.
Dr. Monique Foster of the U.S. Centers for Disease Control and Prevention says it's not unusual for such outbreaks to last one to two years.