Evidence of hepatitis A virus circulation in central Argentina: seroprevalence and environmental surveillance.

Background: Hepatitis A virus (HAV) has shown intermediate endemicity in Argentina, but notification of clinical cases has decreased since the introduction of the vaccine in 2005.

Objectives: In order to get insight into the local circulation of this virus after four years of the official introduction of the vaccine, the aims of this study were to provide information on HAV immune status of the adult population of Córdoba city and to conduct environmental surveillance of HAV in sewage and river samples in the same region.

Study Design: The prevalence of anti-HAV was determined by EIA in 416 samples of people (without prior vaccination) from Córdoba city (2009-2010). Spline regression models were estimated under generalized additive models. Environmental surveillance was conducted in river and sewage samples collected in the same period. Viral detection was performed by RT-Nested PCR of the 5'UTR.

Results: In Córdoba, the global prevalence of anti-HAV was 73.5%. It increased with age (p<0.0001) and it was associated with the low-income population (OR: 1.14; 95% CI 1.05-1.25). This prevalence decreased in younger age groups, especially in the high-income population. Environmental monitoring revealed the presence of HAV (IA) in 20.8% and 16.1% of wastewater and river samples, respectively.

Conclusions: As a consequence of a decrease in HAV circulation due to improvements in immunization, socio-economic and hygienic conditions, young adults are becoming increasingly susceptible to HAV infections. Environmental monitoring demonstrated that HAV circulates in the local population; therefore, health care systems should consider the implementation of preventive measures for susceptible adults in order to reduce the risk of HAV infection.