The Australian and South African listeriosis outbreaks have one thing in common — fatality rates as high as 26 to 28 percent.

Health officials in Victoria, Australia, late last week announced the death of a man in his 80s as the fifth fatality in the country’s listeriosis outbreak. Two others who lost their lives from eating rockmelon, referred to as cantaloupe in the United States, were also Victoria residents. The two others were from Sydney.

Australia’s listeriosis outbreak so far involves 19 confirmed cases, including eight cases in Victoria, six in New South Wales (NSW), four in Queensland, and one in Tasmania. Mostly elderly Australians are infected. The average of the outbreak victims is 78.

Microbiological testing linked the latest death of the Victoria man to the outbreak, along with a recent miscarriage, also in Victoria. Lydia Buchtmann, the spokeswoman for the Food Safety Information Council, says more cases linked to the listeria contamination of rockmelon are likely because the pathogen has an incubation period as long as 70 days. All 19 confirmed cases involve people who ate rockmelon before a recall was initiated.

The NSW Food Authority named the Rombola Family Farm in the Riverina area as the likely source of the contaminated melons. The farm halted production and recalled its melons.

Australian growers anticipate the outbreak will result in new requirements once the NSW Food Authority completes its investigation.

South Africa’s outbreak continues to kill

This chart shows the age distribution and outcome of laboratory-confirmed cases of listeriosis identified from 01 Jan. 1, 2017, to March 12, 2018. N=946 wher age was reported.
Source: South African National Institute for Communicable Diseases

In the much more massive listeriosis outbreak in South Africa, the fatality rate is running at 18 to 28 percent.

The lower number measures the 183 deaths against all Listeria cases going back to Jan. 1, 2017.

Using only the 649 illnesses caused by the outbreak strain results in the higher fatality rate. Other outbreak strains could be identified as investigators continue testing.

South Africa’s listeriosis outbreak is the largest on record, according to the World Health Organization. The source of that outbreak is a low cost processed meat known as “polony.”

The elderly, children, pregnant women and people with compromised immune systems along are most likely to be victims of listeriosis poisoning. Outbreak fatality rates typically range from 20 to 40 percent.