FRIDAY, Jan. 9, 2009 (HealthDay News) -- The source of a salmonella outbreak that has sickened almost 400 Americans in 42 states remains unknown, U.S. health officials said Friday, adding that more cases are expected.
The strain of salmonella has been identified as Salmonella Typhimurium, the most common of the more than 2,500 types of salmonella bacteria in the United States. It's often found in uncooked eggs and meats, said officials with the U.S. Centers for Disease Control and Prevention (CDC), who have been investigating the outbreak for several weeks.
"Cases are continuing to occur, and it is an ongoing investigation," said Dr. Rajal Mody, a CDC Epidemic Intelligence Service officer. "The first people began getting ill in September, but it usually takes several weeks before enough cases have been reported to start noticing a possible outbreak."
While the cause isn't known, Mody said he suspects a food item, possibly produce or a prepared packaged food.
"When you look at the distribution of cases, it does suggest that it could be a mass-distributed food," he said. "This outbreak is on the larger side, but there have been larger outbreaks."
There have been reports of 372 people sickened between Sept. 3 and Dec. 29, 2008, with most illnesses starting after Oct. 1. About 18 percent of those who fell ill were hospitalized. Mody said he couldn't estimate when the outbreak might end, or how many people might eventually become infected with the germ.
Salmonella is typically transmitted through foods that are contaminated with animal feces, Mody said. As part of the investigation, federal health officials are interviewing infected people to see if there were common elements in their diet, he said.
Mody said most reported cases of salmonella occur in children. In the current outbreak, victims have ranged in age from less than 1 year to 103, he said.
An estimated 40,000 cases of salmonella infection are reported each year in the United States, but those are only the reported cases, Mody said. "Those are only the cases that are severe enough to have a person go to a doctor. It's been estimated that the actual number of total salmonella cases could be 30 times or more as great," he said.
Mody said there probably have been many unreported cases in the current outbreak. "If someone has mild symptoms, they might not seek health care," he said.
Most people infected with salmonella develop diarrhea, fever, and abdominal cramps within 12 to 72 hours after contact with the germ. Infections typically clear up in five to seven days, Mody said. "They often don't require any treatment other than making sure you take enough fluids," he said.
But, severe infections can occur, particularly in infants, the elderly, and people with weakened immune systems. In severe cases, the salmonella infection can spread from the intestines to the bloodstream and other parts of the body, causing death unless antibiotics are administered, according to the CDC.
A salmonella outbreak that began last April eventually sickened almost 1,400 Americans, sending nearly 300 of them to hospitals. The outbreak of Salmonella Saintpaul was later traced to jalapeno and serrano peppers imported from Mexico.
To learn more about salmonella, visit the U.S. Centers for Disease Control and Prevention.