Salmonella-tainted cantaloupe is killing Canadians. How scientists track the outbreak

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At least five people in Canada have died in a salmonella outbreak linked to contaminated cantaloupe that scientists have traced to a rare strain of bacteria. 

Federal health and food officials say Malichita and Rudy brand cantaloupes have been identified as the likely source of the outbreak in Canada. Other potentially contaminated brands have been sold in the U.S.

As of Thursday, at least 129 have been sickened in Canada with Salmonella Soahanina, Sundsvall and Oranienburg illness on top of 230 people in the U.S., which has reported three deaths. The true number of sick people is likely much higher since many recover without seeking medical care.

Both the U.S. Centers for Disease Control and Prevention (CDC), and the Public Health Agency of Canada (PHAC), say they're concerned about the extent of hospitalizations. Authorities in both countries are trying to prevent anyone else from eating contaminated fruit, such as diced products from the freezer. 

"There's definitely a strain of salmonella that's causing severe illness," said April Hexemer, an epidemiologist and director of outbreak management with PHAC in Guelph, Ont. 

The level of illness severity is higher than expected for salmonella and more could still be reported, Hexemer said.

"I think the cantaloupe were very highly contaminated," she added.

When an outbreak like this happens, food inspectors race to track down the culprit. In the case of the contaminated cantaloupe, they were able to trace the salmonella back to produce from a few specific companies by checking invoices from Mexico, the U.S. and Canada. The recall process is crucial for stopping the spread of foodborne illness, health officials said.

The Canadian Food Inspection Agency (CFIA) discovered the contamination at the end of October, Hexamer said, and issued its food recall warnings on Nov. 1. The exact cause of contamination is still under investigation.

Children and people aged 65 and older have faced the majority of illnesses in both countries.

"One possible reason behind the high hospitalization rate is that many sick people in this outbreak are in groups that are at higher risk for severe illness," Katia Martinez, a health communication specialist at CDC's division of foodborne, waterborne, and environmental diseases, said in an email.

"At this time, we do not know much about the virulence of the outbreak strains because the strain causing most of the illness in this outbreak is a very rare strain of salmonella in the U.S."

Rare, too, in Canada.