By Amanda Gardner
MONDAY, June 16 (HealthDay News) -- New Mexico, Indiana and one state in Mexico have been cleared as a source of the salmonella-tainted tomatoes that have sickened 228 people in 23 U.S. states since April, according to published reports.
The U.S. Food and Drug Administration has now exonerated 37 states, Puerto Rico and parts of Florida as the source of the outbreak, according to the agency Web site. Six countries -- Belgium, Canada, the Dominican Republic, Guatemala, Israel, and the Netherlands -- also have been ruled out as a contamination source.
The state of Baja California was the first area in Mexico to be certified safe, according to the FDA. Tomatoes grown there can only be exported to the United States if the state agriculture agency has inspected them. Mexico, which harvested 2.3 million metric tons of tomatoes in 2007, accounts for 84 percent of the tomatoes shipped to the United States, Bloomberg News said.
On Friday, the FDA said the bulk of the tomatoes available in the United States at the start of the ongoing salmonella outbreak came from Mexico and Florida.
"The vast majority of tomatoes in national distribution at that time were being produced in one of those two places," Dr. David Acheson, associate commissioner for food protection at the U.S. Food and Drug Administration, said during an afternoon teleconference.
The northern part of Florida has been excluded from the list of possible origins of the outbreak, although central and southern Florida are still a question mark, Acheson added.
Officials also believe it very likely that the contamination arose from one source.
"One thing you learn in science is never to say never. But, based on probabilities, it's extremely likely that the same genetic fingerprint would have come from the same place at the same time," Acheson said. "All of the precedent indicates that this comes from a single geographic region."
The head of the FDA, Commissioner Andrew von Eschenbach, meanwhile, reported in an email that nine of the people who were sickened ate at two restaurants in one chain. He described the cases but would not name the restaurants or their locations.
Asked about that, Acheson would only say, "We're not able to publicly put out the name of the restaurant or specific location, but what I can say is that that obviously represents a small cluster within this outbreak and that information has formed one of the tracks for the trace back."
He added, "We're out where those tomatoes came from that led to illness in those nine patients. That's one of the tracks on the trace back."
U.S. inspectors are currently visiting distributors, suppliers and importers to get pertinent records. They have not yet been sent to any farms because no specific farms have yet been implicated; officials don't yet know whether this is a packing-place problem or a farm problem, Acheson said.
Nor do officials know when they'll have an answer. "We won't know for sure until we get there," Acheson said. "I am confident that we will get to the point where we will definitely be able to say a geographic region. I'm not certain but confident that we will be able to get that far... [But] you can be almost there and something falls apart and then you have to start over. That's happened a number of times."
The number of people sickened in the outbreak remains at 228 in 23 states, with at least 25 hospitalizations, health officials said.
The investigation is categorized as "ongoing," said John Guzewich, senior environmental health scientist at the FDA. But it could take a while to know whether or not infections have ceased.
"The last case of which we are aware, the person became ill on June 1," said Dr. Patricia Griffin, chief of the Enteric Diseases Epidemiology Branch at the U.S. Centers for Disease Control and Prevention. "The [salmonella] incubation period is eight to 48 hours, but it can be a few days more, which means that if that person was one of the many who got sick from a tomato, he or she probably ate the tomato at the end of May. That tomato may have been at the end of its shelf life, or it may have been at the beginning of its shelf life. We're still watching to see whether or not the outbreak is ongoing. Because of delays, it takes us a while to know whether the outbreak is over and not."