Two outbreaks of hepatitis A virus (HAV) with 17 infections are under investigation in Ireland.

A total of 21 patients have been identified during a three-month period in Dublin, with 17 linked to the outbreaks that began in November 2020. One of the outbreak strains has genotype IA.

Three cases of hepatitis A were reported to the Department of Public Health East in mid-November with no direct link between them. Three further patients in late December prompted an incident review meeting.

Four of these patients were linked to an extended family outbreak. The two other sick people lived in the same area of the city, but had no identifiable risk factor for HAV infection or connection to other cases. An outbreak control team meeting was held in mid-January 2021 in response to five more cases from Dec. 23, 2020, to Jan. 13, 2021.

Nine of 21 sick people were hospitalized, 15 are children younger than 18 years old.

The first outbreak includes five children as confirmed cases, two boys and three girls. The index case is likely to have acquired the infection from travel to Central Asia in October 2020. onset of the most recent infection was Dec. 17, 2020.

Dates were the only common item identified from food histories of two cases in this outbreak. Ring vaccination of household contacts was in December 2020 initiated as a control measure against secondary transmission of HAV.

Second outbreak and sporadic infections
The second outbreak includes 12 people with five males and seven females affected. The source of infection of the index case is unknown. All 12 reside in the West Dublin area. The onset date for the most recent illness is late January.

It centers on an extended community living in a large residential site, with evidence of secondary transmission in local schools. School closures as part of COVID-19 restrictions in December 2020 likely reduced further transmission of HAV among children, according to officials.

The Health Protection Surveillance Centre (HPSC) issued an alert on the outbreak to national agencies for infectious disease surveillance in other European countries in mid-February.

A takeaway restaurant was associated with two households in this outbreak. An environmental health inspection of the site was conducted because of sanitation concerns over a blocked sewer system, illegal dumping of domestic waste and stagnant surface water. All three factors were potential contributing factors for transmission of HAV. The drainage problem was repaired by Dublin City Council and testing of drinking water samples were satisfactory.

Mass vaccination of the community living on the residential site was conducted. Out of 180 residents, 136 were vaccinated.

Two of the sporadic cases were linked by a food premises, involving probable transmission of HAV from a pre-symptomatic food handler during their infectious period. The other two infections remain under investigation, with a foodborne source suspected.

No single foodborne source has been identified for either outbreak. Possible environmental transmission of HAV from sewage and stagnant water may have contributed to the second outbreak.

“prompt notification of acute HAV infection to public health departments is essential to ensure timely vaccination of close contacts in order to prevent secondary transmission, and control evolving outbreaks,” said officials.