Two more cases of salmonella have been reported in San Diego County, increasing the total number to nine cases.

Seven San Diego residents and two visitors here have been diagnosed with Salmonella Paratyphi B after eating raw tuna commonly found in sushi.

The cluster of San Diego cases is part of a nationwide outbreak of salmonella poisoning sickening 53 people in nine states.

San Diego County health workers said Friday that most of the people who have become ill live or recently traveled to Southwestern states, like California.

Health officials have not pinpointed an exact cause of the outbreak, but say nearly all of the sick people ate sushi containing raw fish during the week before they fell ill.

Many of those people, San Diego health officials say, ate spicy tuna sushi.

"There is no one specific product that has yet to be identified, but that's the common thread," said Dr. Wilma Wooten, San Diego County's public health officer.

People started getting sick on March 5 and more cases were reported into May nationwide. Patients range from a baby to 83 years old, officials said.

In San Diego, cases broke out in late March and early April, with one person having to be hospitalized, Wooten said.

Salmonella causes diarrhea, nausea, fever and abdominal cramping. The infection lasts about four to seven days and most people recover without treatment, health workers said.

Pregnant women, children and elderly people are encouraged to stay away from eating raw tuna to take extra precautions, Wooten said.

To prevent illness, wash your hands thoroughly with soap and water prior to preparing or eating food and after using the bathroom. Salmonella can be killed by cooking foods to an internal temperature of 165 degrees.

Frank Ursitti, a sports fisherman with H&M Landing, said contamination likely happened while the fish was being processed.

"Before this tuna actually reaches the market or the end user, which could be a sushi bar, it's being handled by several different processors," he said. "The fish is actually being loined or quartered out from there."