More than 30 people fell sick with hepatitis A virus (HAV) infections in a complex outbreak in England involving dates, a school, a bakery, and different transmission routes, according to a study.
In June 2019, Public Health England (now the United Kingdom Health Security Agency) Yorkshire and Humber were contacted by Outwood Academy, a secondary school, with concerns over the illness of three employees.
Prior to the illness of staff, a member of the catering team at the school had been sick for three weeks and reported abnormal liver function tests. Investigations revealed that two ill staff members were positive for immunoglobulin M (IgM) antibodies to HAV (anti-HAV IgM). The following day there were eight anti-HAV IgM-positive cases linked to the school, which has 650 students aged 11 to 18.
One patient worked as a food handler in the school kitchen. Indirect transmission through food from the canteen was considered the most likely route. The outbreak included household and foodborne transmission, according to the study published in Epidemiology and Infection.
Infected food handlers
Thirty-three confirmed patients were part of the outbreak. Of those tested, 31 had the same sequence with an HAV IB genotype. The first three cases were part of the same household: the two earliest ones were household contacts of the food handler who was the first case associated with the school. A further 19 patients, including 16 students and three staff, were linked to the school and indirect exposure to the food handler. One late-onset case resulted in vaccinations at the school.
Five patients were linked to the So! Bar and Eats bakery in Ripon where a case from the household cluster worked part-time as a food server.
There were four cases with no indicated source. One of these was a food handler at a local restaurant and was reported to have been ill at work on the same day as the onset of jaundice. Two other patients were younger siblings of cases who went to Outwood Academy and attended separate primary schools.
The case that worked in the school canteen prepared cold and ready-to-eat food items for six days during the likely infectious period. All 19 patients regularly had food from this canteen.
During an environmental health visit, several areas for improvement in the use of appropriate cleaning products and their management were noted, but no major issues were identified.
Five people were infected through indirect contact with the sick bakery worker during one of three infectious-working days. The store reported that the ill person’s duties were to serve food while wearing gloves and using tongs.
Role of dates
The initial household cluster shared an identical sequence with four other cases in England. These patients lived in different regions and were linked to the consumption of dates. The first patient reported eating dates of the same brand as the sick people from other regions.
A food chain investigation of the dates, imported from Iran, revealed that regular testing for HAV was not standard practice. Suppliers in Iran reported that workers’ hands were tested monthly for HAV but with no positive results. Two samples of dates from the identified brand tested negative.
Control measures in the outbreak included vaccination of household contacts; exclusion of identified patients from school or work and the production of cold, ready-to-eat foods in the school canteen was temporarily stopped. Almost 75 percent of 677 students and 74 of 132 staff at the school were vaccinated in response to the outbreak.
Exposure to HAV at the school and bakery came before awareness of public health authorities that cases worked with food. Breaches of protocols and lapses in hygiene and safe food practices at both workplaces probably contributed to transmission but a specific food item was not found, said researchers.
“This transmission of HAV reinforces the need to promote correct and consistent hygiene practices for all those working with food,” they added.
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Joe Whitworth