On 2 May 2018, Denmark reported a cluster of hepatitis A virus (HAV) infections with the subgenotype IA strain DK2018_231, through the European Centre for Disease Prevention and Control (ECDC)’s Epidemic Intelligence Information System (EPIS) for food- and waterborne diseases and zoonoses (FWD). One of the three confirmed cases had travelled to Morocco. In response, five additional European Union (EU) countries (France, Germany, the Netherlands, Spain and the United Kingdom (UK)) reported cases (n = 20) infected with the same strain between 21 January and 10 April 2018. Concurrently, Germany reported to EPIS that it observed more cases of hepatitis A with travel history to Morocco than expected, compared with the same period in the previous 5 years. Molecular analysis of the HAV VP1/P2A region revealed an unrelated cluster of the HAV subgenotype IB strain V18–16428. Cases infected with this unrelated strain were also reported from France, the Netherlands, Sweden and UK.
The appearance of clusters with a link to Morocco triggered further epidemiological investigations.
The occurrence of the two concurrent HAV clusters in the first 6 months of 2018 serve as a reminder of the risk of contracting hepatitis A in Morocco, a country with intermediate endemicity [4,5]. HAV subgenotypes IA and IB are known to circulate in Morocco and strain DK2018_231 has been observed in sporadic cases with travel history to Morocco in previous years [6–8]. Despite the different characteristics of the two reported clusters, cases with a travel history to Morocco feature in both. In a recent study of European travellers, Turkey, Egypt and Morocco were listed as the top three destinations for acquiring travel-associated hepatitis A and accounted for one third of cases in the period 2009–15 . The epidemiological link to Morocco is more apparent in cluster IB, where the majority of cases had confirmed travelling to Morocco and all interviewed autochthonous cases had reported consuming food items brought home from there.
In the IA cluster, only three cases had travelled to Morocco. However, the large proportion of autochthonous cases and their spatial distribution in this cluster suggest that an imported food item may have served as the vehicle in this outbreak. Large food-borne hepatitis A outbreaks from frozen berries and semi-dried tomatoes have previously affected European countries, further indicating that imported contaminated food products pose a risk to the increasingly susceptible general population in Europe [10–13].
The outbreaks described here illustrate the increased risk that non-immune travellers face when visiting HAV-endemic areas like Morocco. All of the eight countries where cases occurred have explicit recommendations of hepatitis A vaccination for travel to endemic countries, in accordance with World Health Organization (WHO) recommendations [14,15]. Yet it appears that it is not uncommon for people to travel unvaccinated to HAV-endemic countries. An outbreak investigation of hepatitis A in travellers to Egypt between 2012 and 2013 found a high proportion of travellers who were not immunised before travelling [16,17]. Interviews with the German cases have rendered similar results, suggesting that there may be an information gap regarding both the risk of hepatitis A and the availability of a safe and effective vaccine.