Prevalence of hepatitis A virus infection: the paradoxical example of isolated communities in the western Brazilian Amazon region

Abstract

This study evaluated the prevalence of hepatitis A virus infection in the rural area of Lábrea, in the western Brazilian Amazon region. Communities and households were selected randomly. Serum samples were analyzed by means of the immunoenzymatic method for the presence of total antibodies against HAV. The study included 1,499 individuals. The prevalence of anti-HAV was 74.6% (95% CI 72.3-76.8). Univariate analysis showed associations with age (chi-square for linear trend = 496.003, p < 0.001), presence of outside toilet (p < 0.001), history of hepatitis (p < 0.001) and family history of hepatitis (p = 0.05). After adjusting for age, HAV infection also showed an association with the number of people in the family (p = 0.03). The overall prevalence rates were high, but not more than 60% of the children under the age of ten years had already been infected. Very high prevalence was detected only within older cohorts, thus paradoxically defining this as a region with intermediate endemicity, even under the conditions of poverty encountered. Key-words:Hepatitis A virus. Epidemiology. Prevalence. Amazon region. Brazil. RESUMOEste estudo avaliou a prevalência de infecção pelo vírus da hepatite A na área rural de Lábrea, Amazônia Ocidental Brasileira. Comunidades e domicílios foram selecionados aleatoriamente. Amostras de soro foram analisadas pelo método imunoenzimático para os anticorpos totais contra o vírus da hepatite A. O estudo incluiu 1.499 indivíduos. A prevalência do anti-HAV foi 74,6% (IC 95% 72,3 a 76,8). Análise univariada mostrou associação com idade (qui-quadrado de tendência linear = 496,003, p<0,001), presença de sanitário fora do domicílio (p<0,001), passado de hepatite (p<0,001) e história familiar de hepatite (p=0,05). Depois de controlado por idade, a infecção pelo VHA mostrou também associação com o número de pessoas na família (p=0,03). A prevalência global mostra taxas elevadas, entretanto não mais do que 60% dos menores de 10 anos, já são infectados, e prevalências elevadas são detectadas em coortes de mais idade, mostrando paradoxalmente uma definição de região de endemicidade intermediária, mesmo nas condições de pobreza encontradas. Palavras-chaves:Vírus da hepatite A. Epidemiologia. Prevalência. Região amazônica. Brasil.

Declining prevalence of hepatitis A virus antibodies among children from low socioeconomic groups reinforces the need for the implementation of hepatitis A vaccination in Brazil

“…This region is known to be highly endemic for HAV with seroprevalence rates as high as 90% among children that are 10 years old or younger (Bensabath et al 1987, de paula et al 2001, Assis et al 2002. Our results are in agreement with results from Braga et al (2009), who demonstrated an intermediate pattern of HAV infection in isolated communities in the western Brazilian Amazon region. This unexpected intermediate pattern of HAV infection could be explained by the isolation of these small villages, resulting in a decreased contact with the outside world in childhood.…”

Epidemiological and serological aspects of hepatitis A among children and teenagers in the city of Santos: a cross-sectional study

“…In Vila Velha, Espírito Santo, 21 there was a correlation between positive serological tests for hepatitis A and lower access to filtered water, lower access to the sewage system, habits of swimming in rivers or the sea and a greater number of people living in the same room. In the Brazilian Western Amazon region, 16 it was also associated with a greater number of people in the family. In Greece, 22 In our series, we observed that a large number of teenagers were at high risk of infection, because even with the gradual increase in prevalence of anti-HAV IgG antibodies, it remained low.…”

Progression of the load of waterborne and intestinal parasitic diseases in the State of Amazonas

“…Although hepatitis A morbidity has declined progressively in Brazil as a whole, it remains high in the Amazon region. In Labrea, the prevalence of anti-HAV was 74.6%, showing associations with age, the presence of outside toilets, history of hepatitis, family history of hepatitis, and the number of people in the family (31) . Other studies conducted in the Brazilian Amazon showed anti-HAV prevalences greater than 90% (32) (33) .…”