Baby spinach under the Fresh Attitude brand is being recalled in Ontario and Quebec over possible salmonella contamination.

Lambton County's public health unit says there are 33 confirmed cases related to the outbreak at Barakat restaurant in Sarnia.

Wastewater surveillance works because many infectious agents are excreted in bodily fluids, before and during active infection, says Lawrence Goodridge of the University of Guelph.

The CFIA says consumers or businesses that have the products should throw them out or return them to the place of purchase.

The PHAC closed its investigation on Oct. 1, saying in total, there were 515 confirmed cases of Salmonella Newport illness linked to this outbreak across Canada.

Some of the individuals who became sick reported feeding their dogs PawsUp! and Western Family brands of pig ear dog treats before getting salmonella.

The Canadian Food Inspection Agency says the products were distributed across Ontario.

Officials said there was 'no evidence to suggest that onions grown in Canada' were associated with the outbreak.

The advisory was triggered by a recall on peaches with certain brand names in the United States at Prima Wawona's Fresno, Calif., location on Friday. Various importers have followed suit.

Health officials say that a specific cause of the outbreak has not been identified.