Those Mysterious Salmonella Outbreaks

December 5, 2008

Several times this autumn – most recently on October 24th – the Public Health Agency of Canada advised Canadians that it was investigating a national outbreak of Salmonella Poona. As of the last report, the same strain of Salmonella Poona had turned up 29 patients in five provinces.

That outbreak must have ended, because PHAC has been "mum" on any new cases since October 24th. And, as best we can tell, the source of the unusual flurry of infections was never found.

Now New Zealand is searching for the source of a national outbreak of Salmonella Typhimurium, phage type 42. According to yesterday's news release from the Ministry of Health, 36 New Zealanders have been infected with this strain of Salmonella since October 13th – more than double the total for all of 2007. While the victims are located on both the North and South Islands – in Dunedin (9), Christchurch (16), Nelson (5), Greymouth (1), Rotorua (1), Whakatane (1), Waikato (1) and Auckland (2) –  most live on the South Island.

The broad geographic distribution of cases suggests a common food source. The duration of the outbreak (since mid-October) hints at a food that is not highly perishable – or at an ongoing source of contamination of a perishable food. At the moment, it's up to the epidemiologists to narrow the scope of the search.