Listeria sickens more than 550, leaves 36 dead in South Africa

A major outbreak of listeriosis has sickened more than 550 people in South Africa, with a reported 36 deaths due to the illness.

The large outbreak is highly unusual for the country. In a typical year, South Africa records just 60–80 cases of listeriosis. Authorities are currently investigating the source of this outbreak, which has been ongoing since the beginning of 2017.

“We believe for this particular outbreak the most likely possible source is contamination of food at its origin (e.g., farms and agriculture), as well as food processing plants,” said Aaron Motsoaledi, South Africa’s Minister of Health.

Listeriosis is the illness caused by Listeria, a foodborne pathogen associated most commonly with ready-to-eat meats and unpasteurized dairy products. Its symptoms are fever, neck stiffness, confusion, weakness and vomiting.

Though usually the illness passes after a few days without treatment, it can lead to infection of the bloodstream and brain, which can be deadly.

The age group most affected by the South African outbreak is babies fewer than 28 days old; 37% of those who have fallen ill fit into this group. Infants, elderly people, and those who are immunocompromised (such as cancer patients or other people dealing with other illnesses) face the highest health risk from Listeria and other foodborne pathogens.

Outbreak investigators are using whole genome sequencing (WGS) to find the source of the contamination, a process that reveals the entire DNA structure of an organism. In this case, investigators hope to be able to identify the particular variation of Listeria that has been making people sick. So far, 15 different sequence types of Listeria have been identified, with the majority belonging to just one of those types.

With that information, it becomes possible to begin tracing where the bacteria came from by looking the particular variant in other foods or food production sites.

Click here to read about the challenges Listeria poses to the food industry.

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