The Salmonella Agona bacteria causing illnesses linked to imported papayas also cropped up in 2010, the Centers for Disease Control and Prevention reported Tuesday, but the source of that outbreak was never found.

According to the CDC’s latest update, the outbreak strain is made up of four closely related pulse-field gel electrophoresis (PFGE) patterns that have rarely been seen in PulseNet, the nationwide surveillance system that identifies clusters of foodborne disease by their DNA fingerprints. Three of the patterns were first seen a year ago. 

Between May 28 and Sept. 10 last year, 119 cases of Salmonella Agona were reported to the CDC by 14 states. The profile of that outbreak  — the “distribution of age, sex, ethnicity and state of residence among ill persons” — was similar to the current outbreak, the CDC wrote.

However, the source of that outbreak was not determined, despite an “intensive investigation during the summer of 2010 by local, state and federal public health agencies that focused on fresh fruit, including papaya,” the CDC said.

In its report Tuesday on the current outbreak, the federal public health authority said 99 people are now confirmed to be infected with Salmonella Agona traced to Mexican papayas. The two additional cases were reported from New York and Pennsylvania.  Eleven of the case patients told health investigators they’d traveled to Mexico in the week before they became ill.

The epidemiological, traceback and lab investigations concluded the outbreak source to be whole papayas imported by Agromod Produce of McAllen, Texas. The outbreak strain was detected in produce samples taken at the processing plant in McAllen and on papayas at the U.S. border that were headed to Agromod.

In addition to the two samples that tested positive for the outbreak strain, the Food and Drug Administration found 10 other papaya samples from Mexico to be positive with different strains of Salmonella; none of those sampled lots entered the United States, the FDA said.

Agromod, which distributes papayas under four brand names — Blondie, Yaya, Ma√±anita, and Tastylicious — has withdrawn its papayas from the market in the U.S. and Canada, although the CDC warns that contaminated papayas may still be in stores and consumers homes. The FDA also advises that while Agromod sold whole papayas, the fruit could have been further processed as it moved along the supply chain.

There’s still no word on how the papayas became contaminated.