New Zealand data shows an increase in foodborne infections

New Zealand has reported a rise in most major foodborne infections in 2022, according to recently published data. 

The data comes from EpiSurv, the notifiable disease surveillance system, and the Ministry of Health’s database on hospitalizations, which are separate. It was published by New Zealand Food Safety (NZFS), a Ministry for Primary Industries (MPI) unit.

Most 27 outbreaks, with 253 cases in 2022, were linked to commercial food operators, and only five were associated with food prepared in consumer homes. There was also a nationwide Vibrio parahaemolyticus outbreak with 60 cases which did not have a familiar location or supplier.

Campylobacter, Salmonella, Shiga toxin-producing E. coli (STEC), and Listeria infections increased in 2022 from 2021 levels. Reasons suggested include more overseas travel and easing restrictions put in place during the COVID-19 pandemic.

Campylobacter and Salmonella
There were 5,878 Campylobacter cases, with 4,148 estimated to be foodborne and 999 hospital admissions.

The highest notification rate was reported for children aged 1 to 4, while the highest hospitalization rate was for those aged 70 and over. There were 128 notifications in EpiSurv listing overseas travel as a risk factor, compared to 394 in 2019, 66 in 2020, and seven in 2021.

Eleven outbreaks in EpiSurv had 94 cases, and three listed food as a possible transmission mode. New Zealand Food Safety investigated two more outbreaks. Two were linked to chicken, one to shrimp, and another to liver or unpasteurized cheese. For the second consecutive year, no outbreaks were associated with raw milk.

There were 750 Salmonella cases, with 371 estimated to be foodborne and 212 hospital admissions.

In 2022, 120 notifications in EpiSurv listed overseas travel as a risk factor, compared to 349 in 2019, 49 in 2020, and none in 2021. Notification and hospital admission rates were highest for children in the younger than 1 year old age group.

Isolates from 654 notified cases were typed. Salmonella Typhimurium was the most common, followed by Salmonella Enteritidis and Salmonella Bovismorbificans.

Of five outbreaks, three reported food as a possible mode of transmission. One Salmonella Typhimurium incident affected 25 people and was related to travel to Fiji, airport, or airplane food. The other two included 13 cases, of which eight were hospitalized, with four in each outbreak. New Zealand Food Safety investigated two further clusters of salmonellosis cases.

One outbreak was associated with imported sesame-based products. Sequencing of clinical isolates showed cases were the same sequence type and closely related to a European outbreak linked to sesame products from Syria. The outbreak led to a recall of tahini and halva. Product testing identified the presence of Salmonella Kintambo, Salmonella Amsterdam, and Salmonella Orion.

E. coli and Listeria
There were 1,022 E. coli infections, with 390 estimated to be foodborne. One death and 67 hospitalizations were recorded.

The STEC infection notification rate was highest for the 1 to 4-year-old age group, followed by the under-1-year-old age group. Isolates from 694 notified cases were typed. Of the 707 typed isolates, 259 were E. coli O157, and 448 as non-O157. As in previous years, the most frequent non-O157 serotypes were E. coli O26:H11 and E. coli O128:H2.

19 STEC cases were reported to have developed hemolytic uremic syndrome (HUS). The associated serotypes were mainly O157:H7 and O26:H11.

Of five outbreaks, one with three sick people had food as a possible transmission mode. It was linked to a prosciutto or meat pizza from a mobile food unit.

39 Listeria infections and six deaths were reported in EpiSurv, but hospital data showed 40 hospital admissions. Notification and hospitalization rates for listeriosis were highest in the over 70’s age group.

One outbreak started in December 2021 but was reported in 2022. It had two confirmed cases and one death. Paneer cheese was identified as the probable source. Listeria was detected in batches of the product, and a recall was initiated.

Other agents and outbreak highlights
One person was reported with a Bacillus lichenoformis and Bacillus megaterium infection. A vegetable samosa from a food service outlet was the suspected source as the food had an unpleasant odor. Laboratory testing of the samosa was positive for Bacillus spp.

A total of 35 hepatitis A cases were reported in a national outbreak associated with imported frozen berries. The incident continued into 2023. Of cases in 2022, seven had no recollection of eating imported frozen berries and were likely due to secondary transmission. Hepatitis A virus was detected in an opened bag of frozen berries from one patient.

Five norovirus outbreaks recorded food or a food handler as a possible transmission mode. Health officials investigated another two outbreaks. Suspected sources included salad and oysters.

Sixty patients were part of a Vibrio parahaemolyticus outbreak from 2021 to 2022. Forty sick people reported eating raw or partially cooked seafood. One histamine outbreak affected two people. New Zealand Food Safety also conducted two other investigations of suspected histamine (scombroid) fish poisoning, including one of three cases in February and one of six cases in April 2022.

Two hospital admissions for ciguatera poisoning were recorded. Two suspected cases of toxic shellfish poisoning were reported. One case had raw, recreationally gathered kina, and the other consumed prawns, clams, and scampi.

Clostridium perfringens caused one outbreak with five patients. The incident related to potentially undercooked chicken nuggets supplied to schools. One Shigella outbreak with two cases recorded dried tuna from the Pacific Islands as a possible source of infection. One Giardia outbreak with four sick was linked to raw milk, but no milk samples were taken. Cases also lived on a farm, so that animal contact may have been a factor.

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