New Zealand recorded a mixed picture of foodborne infections in 2023, with some declining but others rising.
A report from the Institute for Environmental and Scientific Research (ESR) found that cases of Campylobacter and Salmonella were increasing The number of Listeria and E.coli infections will have decreased in 2023.
The data comes from EpiSurv, the notifiable disease surveillance system, and the Ministry of Health’s database on individual hospital admissions.
A total of 827 Salmonella cases were recorded. This drops to 325 if we use the estimates for domestically acquired foodborne infections.
The reporting rate for men was slightly higher than for women. The number of hospital admissions was higher for women than for men. The number of reports and hospital admissions of salmonellosis was highest in children under 1 year of age.
The ESR Enteric Reference Laboratory characterized isolates from 827 reported cases. Salmonella Typhimurium and Salmonella Enteritidis were the most common serotypes identified.
Three of the five outbreaks had foodborne risk factors: one event involving two children from the same household cited handling raw meat and chicken during meal preparation as a risk factor. A second outbreak of 15 cases was linked to a community event offering a shared “bring a plate” meal. Another outbreak of two cases was linked to a milkshake or homemade pork, but the source was not confirmed.
E. coli and Listeria numbers
In 2023, 1,006 cases of Shiga toxin-producing E. coli (STEC) were registered. However, this number drops to 366 if the estimates for domestically acquired foodborne infections are used.
The number of reports and hospital admissions was higher for women than for men. The STEC infection rate was highest in the age group under 1 year, followed by the age group 1 to 4 years. The number of hospital admissions was highest in the age groups under 1 year, 1 to 4 years and 70+.
Three outbreaks involving 14 cases were reported, but none were due to food eaten in New Zealand.
The ESR Enteric Reference Laboratory characterized isolates from 603 STEC-infected cases. Of the 616 isolates typed, 134 were STEC O157:H7. As in the previous three years, the most important non-O157:H7 serotypes were O26:H11 and O128:H2.
Data from EpiSurv showed that 17 cases developed hemolytic uremic syndrome (HUS). The corresponding serotypes were eight O157:H7, four O26:H11 and one O104:H7.
Thirty-seven cases of listeriosis were reported in EpiSurv. Hospital admission data showed 40 cases. Five non-pregnancy-related cases and two perinatal cases died with listeriosis as the primary cause of death.
The number of reports and hospital admissions was higher for men than for women, and highest in the 70+ age group. No outbreaks have been reported.
In 2023, 6,089 cases of Campylobacter were recorded, but this number drops to 4,010 if we use the estimates for domestically acquired food-borne infections. A total of 989 people were hospitalized and no cases were recorded with campylobacteriosis as the main cause of death.
Outbreaks at a glance
Two cases of Bacillus cereus intoxication have been reported in EpiSurv. There was one outbreak with twelve cases involving both Bacillus cereus and Clostridium perfringens. The suspected source was chicken curry from a catering service. Inadequate meal cooling by the caterer or the consumer may have been the cause.
There were three outbreaks of Clostridium perfringens intoxication with 27 cases. One was linked to chicken curry, the second to chicken lamb souvlaki, and the other remained unsolved.
Four additional cases of hepatitis A were reported during the major outbreak linked to imported frozen berries announced in 2022. Between June 2022 and April 2023, 39 infections were observed.
There were six norovirus outbreaks, all reporting food or a food handler as a possible mode of transmission. In two outbreaks, unwell food handlers were the likely source of illness, while one was linked to crayfish sandwiches.
One Shigella outbreak with two cases was part of an international event linked to a flight from the United Arab Emirates. Food on the plane was the suspected source of illness. Another outbreak involving three patients was linked to imported frozen raw cinchona.
Three hospitalized cases of Ciguatera poisoning were recorded. There were also two suspected outbreaks of shellfish poisoning. In two cases linked to the first outbreak, steamed mussels from a catering establishment had been consumed. The seven cases in the second outbreak had eaten oysters. However, the symptoms were more consistent with a bacterial or viral infection. Patients consumed oysters before a recall due to the detection of paralyzing 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 on-site investigation took place and control errors were resolved.
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