The hepatitis A virus still represents a major public health problem. HAV is a significant cause of morbidity and socioeconomic losses in many parts of the world, while it can result in fulminant hepatitis and death, albeit rarely [
12]. HAV has been reported to have an inherently more stable molecular structure than other picornaviruses and thus is characterised by high resistance to the environment and is able to persist for extended periods on environmental surfaces [
2]. The incidence of HAV infection varies considerably among and within countries [
1]. In the present study, HAV subgenotype IA was detected in sewage samples collected from the biological treatment plants of two urban cities (Patras and Alexandroupolis) in northern and southern Greece. Different patterns of HAV endemicity have been detected in the cities of Cairo and Barcelona, while the circulating strains as characterized by the analysis of sewage samples were genotype IB [
6]. A similar study, performed in order to depict HAV strains in Barcelona, from both environmental and clinical samples, revealed a 95% prevalence of genotype I, with nearly 50% being either subgenotype IA or subgenotype IB. Interestingly, in the year 2000, although the number of cases of hepatitis A has been estimated to be less than 15-30 per 100000 habitants, 80% of urban sewage samples studied showed the presence of HAV. This was attributed to the fact that faecal shedding of HAV can last for months after the resolution of symptoms, and patients could be a source of further virus spreading within the community [
11]. Analysis of the environmental and clinical isolates of our study showed the presence of HAV strains belonging to genotype IA. Subtype IA appears to be responsible for the majority of hepatitis A cases worldwide, whereas subtype IB viruses have been found in the Mediterranean region [
1]. A study of molecular analysis of HAV isolates in Albania has shown that the unique genotype present in Albania is genotype IA [
13]. In another study in Albania, only genotype IA was characterized in all the analysed samples of sewage and sera of patients involved in an HAV outbreak [
14]. A study from another Mediterranean country, Tunisia, showed that all Tunisian strains belonged to genotype I with a greater presence of sub-genotype IA (98%) and 2% of sub-genotype IB [
15].
The hepatitis A vaccine is included in the Greek National Immunization Program (GNIP) and universal vaccination is recommended for all children over 12 months of age [
8]. With regards to hepatitis viruses, moving populations such as Roma and refugees constitute special target groups of any population coverage program, as the underlying unfavourable living conditions could facilitate the spread of the infections [
12]. Over the past two decades there has been a significant increase in immigration from Eastern Europe and the Balkan countries to Greece. As a result, immigrants of these countries of origin currently comprise 10% of the Greek population [
8]. Moreover, due to recent large immigration flows from North Africa and Asia, through Turkey, to Greece, a new epidemiological pattern may emerge in the near future. Data from the occurrence of viruses in sewage may provide an overview of the epidemiology of viral infections circulating in the community, and at the same time reveal the occurrence of asymptomatic infections in the population [
6].