New Zealand recorded a mixed picture of foodborne infections in 2023, with some going down but others rising.
A report from the Institute for Environmental and Scientific Research (ESR) showed that Campylobacter and Salmonella cases increased while Listeria and E. coli infections declined in 2023.
Data comes from EpiSurv, the notifiable disease surveillance system, and the Ministry of Health’s database on separate hospitalizations.
A total of 827 Salmonella cases were recorded. This falls to 325 when using the estimates for domestically acquired foodborne infections.
The notification rate for males was slightly higher than for females. The rate of hospitalized cases was higher for females compared to males. The notification and hospital admission rates of salmonellosis were highest for children under 1 year old.
The ESR Enteric Reference Laboratory typed isolates from 827 notified cases. Salmonella Typhimurium and Salmonella Enteritidis were the most common serotypes identified.
Three of the five outbreaks had foodborne risk factors: One event affecting two children from the same household listed handling raw meat and chicken during meal preparation as a risk factor. A second outbreak of 15 cases was associated with a community event that included a shared “bring a plate” meal. Another outbreak of two cases was linked to a milkshake or home-cooked pork, but the source was not confirmed.
E. coli and Listeria figures
In 2023, 1,006 Shiga toxin-producing E. coli (STEC) cases were recorded. However, this number drops to 366 when using the estimates for domestically acquired foodborne infections.
Notification and hospitalized case rates were higher for females than for males. The STEC infection rate was highest for the under 1-year-old age group, followed by 1 to 4-year-olds. The hospitalized case rate was highest for the under 1 year-old group, 1 to 4-year-olds, and 70+ age groups.
Three outbreaks with 14 cases were reported, but none were due to food eaten in New Zealand.
The ESR Enteric Reference Laboratory typed isolates from 603 cases infected with STEC. Of the 616 typed isolates, 134 were STEC O157:H7. As in the previous three years, the top non-O157:H7 serotypes were O26:H11 and O128:H2.
EpiSurv data showed that 17 cases developed hemolytic uremic syndrome (HUS). The associated serotypes were O157:H7 eight times, O26:H11 four times, and O104:H7 once.
Thirty-seven cases of listeriosis were reported in EpiSurv. Hospitalization data showed 40 cases. Five non-pregnancy-related and two perinatal cases died with listeriosis as the primary cause of death.
Notification and hospitalized case rates were higher for males than for females, and they were highest in the 70+ age group. No outbreaks were reported.
In 2023, 6,089 Campylobacter cases were recorded, but this number drops to 4,010 when using the estimates for domestically acquired foodborne infections. Overall, 989 people were hospitalized, and no cases were recorded with campylobacteriosis as the primary cause of death.
Outbreaks round-up
Two cases of Bacillus cereus intoxication were reported in EpiSurv. There was one outbreak with 12 cases that involved both Bacillus cereus and Clostridium perfringens. The suspected source was chicken curry from a catering service. Possible inadequate meal cooling at the caterer or the consumer was the cause.
There were three Clostridium perfringens intoxication outbreaks with 27 cases. One was linked to chicken curry, the second to chicken lamb souvlaki, and the other remained unsolved.
Four additional Hepatitis A cases were reported in the large outbreak associated with imported frozen berries announced in 2022. 39 infections were seen between June 2022 and April 2023.
There were six outbreaks of norovirus, all of which reported food or a food handler as one possible mode of transmission. Unwell food handlers were the likely source of illness in two outbreaks, while one was linked to crayfish sandwiches.
One Shigella outbreak with two cases was part of an international event associated with a flight from the United Arab Emirates. Food on the plane was the suspected source of illness. Another outbreak with three patients was linked to imported frozen raw kina.
Three hospitalized cases of Ciguatera poisoning were recorded. There were also two suspected shellfish poisoning outbreaks. Two instances associated with the first outbreak had consumed steamed mussels from a food service outlet. The seven cases in the second outbreak had eaten oysters. However, symptoms were more consistent with a bacterial or viral infection. Patients consumed oysters before a recall due to the detection of paralytic shellfish poison in the growing area.
One outbreak of suspected scombroid fish poisoning, with two cases, was traced to smoked fish from a supermarket. Leftover fish samples were sent to ESR for testing, and high histamine levels were confirmed. An onsite investigation occurred, and control failures were resolved.
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