Seroepidemiology of Hepatitis A Virus Among Filipinos Living in Selected Communities in and Around Metro Manila

Abstract

One thousand (1000) Filipinos residing mostly in middle class subdivisions in and around Metro Manila were tested for the presence of antibodies to the hepatitis A virus. Both sexes, ages ranging from one year to seventy nine were included in the study. Students comprised 40% of the participants. 82% of whom were enrolled in private schools. The rest were gainfully employed, mostly office workers, young executives and professionals. Overall, the data show an increasing HAV antibody positivity with age in children less than five years of age; anti-HAV positivity is only 10%. This figure doubles by age ten. By age fifteen, 42% are anti-HAV positive, and before the age of twenty, more than half or 54% tested anti-HAV positive. The positivity continues to increase in 10-15% increments until the age of forty, and from then onwards, positivity ranges from 89-96%. These figures tell us that among adults > 40 years old, some 4-11% have no detectable antibodies to HAV, and are therefore still susceptible to HAV infection. Anti-HAV positivity for all age groups is 62%.

Of the HAV antibody positive individuals, only 15% had a history of jaundice, which only confirms that the majority of cases are subclinical. The results of this study show a relatively high endemicity of Hepatitis A infection in Metro Manila. The figures we obtained from this seroprevalence study are comparable with data obtained in Bangkok, Thailand where anti-HAV positivity among children attending primary schools is 22-69%. In urban areas in Malaysia, figures may be in the range of 50-55% for all age groups which approaches that of our data. These are in contrast to the statistics obtained in Singapore in 1985 where overall anti-HAV positivity was 32%. Obviously, differences in standards of living and general sanitation explain the contrasting figures.

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