As of 12 January 2018, a total of 748 laboratory-confirmed listeriosis cases have been reported to the National Institute for Communicable Diseases (NICD) since 01 January 2017. Final outcome data are available for 160 of the patients, of whom 67 have died. Most cases have been reported from Gauteng Province, followed by Western Cape and KwaZulu-Natal provinces.
This is the largest documented listeriosis outbreak South Africa has ever experienced. All available resources are being directed to outbreak investigation activities and interventions. The national departments of Health, Agriculture, Forestry and Fisheries, and Trade and Industry are working closely with agriculture and food industry stakeholders to intensify investigation efforts aimed at identifying the possible source/s of the outbreak, whilst enhancing food safety interventions.
Genetic testing on samples of Listeria from patients diagnosed with the disease suggests that a single strain of the bacteria, sequence type 6 (ST6), is responsible for the majority of infections. This implies that a single source of food contamination is causing the outbreak, i.e. a single widely consumed food product, or multiple food products produced at a single facility.
On 15 December 2017, listeriosis became a notifiable medical condition in the country.
Listeria is a bacterium that is naturally found in the environment. It commonly occurs in soil, water, vegetation and in the feces of some animals. It can contaminate a wide variety of food types, including meat and meat products, dairy products (unpasteurized and pasteurized), fresh and frozen produce (fruits, vegetables and sprouts) and ready-to-eat products. This fact, coupled with a variable incubation period that can range from 6 hours to 70 days, poses a major challenge in determining the source of the outbreak.
Given the recent focus on raising awareness of listeriosis amongst the general public, it is important to reiterate a few key points regarding this disease:
- Listeria cannot be spread from person to person.
- Listeria infection follows consumption of contaminated food, or is transmitted from a pregnant mother to her unborn fetus.
- Most healthy people who consume food contaminated with Listeria do not get ill. When persons do get ill, they develop either self-limiting gastroenteritis that presents with fever and diarrhea, which usually resolves on its own without medical intervention, or more severe illness including meningitis, bacteria in the blood, and pregnancy associated complications.
- Only a small group of the population are at risk of severe illness due to Listeria infections. This group includes pregnant women, babies under the age of one month, people over the age of 65, and anyone with a weakened immune system (including people who have HIV, those with cancer, people who have kidney or liver diseases, those with diabetes, and people taking certain medications that suppress the immune system – such as corticosteroids or chemotherapy).
- Pregnant women are an important high-risk group, as they may transmit the infection to the unborn child. Meningitis and blood infections are the important severe forms of listeriosis.
Health officials note that persons who are infected with Listeria pose no risk to other people and that the current outbreak poses minimal threat to tourists in the country.
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