South African illness data shows outbreaks often not investigated

The latest foodborne illness figures and examples of outbreaks have been shared in South Africa.

The GERMS-SA 2023 annual review was compiled by the National Institute for Communicable Diseases (NICD). Reporting of all cases of category 1 diseases in the Notifiable Medical Conditions (NMC) platform by healthcare workers and laboratories is mandatory.

A total of 83 cases of listeriosis were reported through the NMC surveillance system in 2023. In 2022, 88 cases were recorded. Five deaths and one pregnancy associated case that resulted in a still-birth were reported.

In 2023, Western Cape, Gauteng, and KwaZulu-Natal reported 86 percent of the cases. Patients were mostly aged 15 to 49 but 21 were younger than 28 days.

Listeriosis case investigation forms were completed for 19 patients. Six deaths were reported and pregnancy associated infections accounted for six cases, all resulting in live births.

NICD said the number of patients is below the expected annual range of cases of 119 to 298 based on the estimated incidence of sporadic infections.

Salmonella and Campylobacter
A total of 3,162 cases of non-typhoidal salmonellosis were reported through the surveillance program. This includes more than 2,100 non-invasive and 1,033 invasive cases. The overall figure was similar to the 3,185 cases in 2022.

In 2023, the most cases of invasive disease were reported from Gauteng, followed by the Western Cape, and KwaZulu-Natal. These three provinces also recorded the most non-invasive cases.

Non-invasive disease was highest in children younger than 5, followed by people aged 35 to 44 and those older than 65. Invasive disease was most common in people aged 35 to 44, followed by children younger than 5, and those aged 25 to 34.

In total, 2,251 viable isolates were received and serotyped. A total of 74 serovars were identified, but Salmonella Enteritidis and Salmonella Typhimurium accounted for 76 percent of the cases. The next most common types were Salmonella salamae, Salmonella Isangi, Salmonella Muenchen, and monophasic Salmonella Typhimurium.

“Provincial differences in serovar proportions might reflect local transmission dynamics or undetected outbreaks and requires further investigation,” said NICD.

There were 694 isolates of Campylobacter submitted through the surveillance program compared to 804 isolates in 2022.

In 2023, Gauteng Province reported more than half the cases, followed by the Western Cape. These two provinces accounted for 86 percent of the total infections.

Patient numbers were highest in children younger than 5 and Campylobacter jejuni was the most common species identified by PCR testing.

Outbreak examples
In an overview for 2023 and 2024, the NICD said it responded to 10 food- and waterborne outbreaks with epidemiological and laboratory testing support. A total of 195 outbreaks were reported with 132 confirmed as foodborne. Gauteng had the most outbreaks with 38 while KwaZulu-Natal had 36 and the Eastern Cape had 19.

Many outbreaks were not investigated because of insufficient epidemiological data and the absence of clinical, food, and environmental sample collection and testing. Clinical specimens were collected in 52 outbreaks and pathogens were isolated on 20 occasions. At 10 times, Salmonella was the most common pathogen found.

In August 2023, a visiting doctor at a home for elderly people with intellectual and physical disabilities in Gauteng reported a suspected foodborne outbreak involving 24 residents. Two people were admitted to hospital, one of whom died.

Six specimens were collected from sick residents and food retention samples, including boiled eggs and chicken meals, were sent to a private lab for screening of foodborne pathogens. All clinical samples tested positive for Salmonella Enteritidis. Lab results for food samples were not shared. The facility conducted extensive investigations and reinforced infection control measures throughout the food preparation processes.

In October 2023, 12 inmates fell ill while attending an event at a Western Cape correctional facility.

During transit to the Western Cape, inmates from a facility in KwaZulu-Natal consumed cooked food from a visitor. Onset of illness occurred during transit. Ten stool samples were collected and one patient was admitted to hospital. Salmonella was isolated from nine samples and Salmonella Enteritidis was confirmed. Food samples were not available for testing.

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