Abstract
Background and Aims: Hepatitis A virus infection (HAV) has a world-wide distribution and affects infants and young children in developing countries but epidemics are rare; whereas hepatitis E virus infection (HEV) is restricted to tropical countries and affects older children and young adults and epidemics are common. Exposure rates for HEV are different in various regions of India and different in various socioeconomic groups of the country. In previous series from Western India, age-specific HEV exposure rates were as follows: a. In 1993 (Mumbai) - 5% at age < 20 years and 17.5% at age > 20 years; b. In 1998 (Pune) - 5.6% at age < 25 years and 35.3% at age > 25 years.
Methods: In December 2003, an epidemiological survey (total number= 1163 persons, mean age= 28.9 ± 9.2 years, male: female ratio= 0.9: 1, middle and high socio-economic class) was carried out in two western railway residential colonies of Mumbai. To detect the exposure rate for HEV and HAV, serological tests for IgG antiHEV and IgG antiHAV were carried out in all individuals. An epidemic of HEV mainly affecting middle or high socio-economic class was noted after 10 months of this survey (from October 2004 to February 2005) in Mumbai, India. During the HEV epidemic, a total of 140 patients were visited at Bombay Hospital (mean age= 35 ± 12 years, male: female ratio= 1.2: 1). For comparison, 140 patients (mean age=32.44 ± 9 years, male: female=0.9: 1, middle and high socio-economic class) with sporadic HEV, visited from February 1999 to October 2004, were analyzed. These data were analysed using chi square test.
Results: Overall exposure rates for HEV and HAV were 35.76% and 87.18% respectively. Age-specific exposure rates for HEV and HAV were as follows, respectively: age groups- 0-10 years: 17.75% and 59.17%; 11-20 years: 25.08% and 86.76%; 21-30 years: 41.71% and 94.65%; 31-40 years: 43.28% and 94.02%, 41-50 years: 42.02% and 93.08%; 51-60 years: 57.42% and 94.05%; and > 60 years: 40% and 96.6%. Age-specific exposure rates (HEV and HAV) for the age group ≤ 20 years (456 persons) were 22.36% and 76.53%, and for the age group > 20 years (707 persons) were 44.41% and 94.05%, respectively. Age distribution of epidemic and sporadic HEV, respectively, was as follows: age group ≤ 20 years-:12.14% and 17.85%; 21-40 years: 58.57% and 53.57%; and > 40 years: 28.57% and 27.85%.
Conclusions: HEV age-specific exposure rates suggest the presence of high endemicity and age-infection curve parallel to HAV, but at a lower level of seroprevalence. Exposure rates of HEV have increased significantly in all age groups as compared to previous data, especially in the age group < 20 years. Age distribution of cases in epidemic and sporadic HEV is similar.
Keywords
Seroepidemiology Age-Specific Seroprevalence Hepatitis A Hepatitis E
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