Hepatitis A virus infection -- shifting epidemiology.

Objective Of The Study: To determine the age distribution in HAV infection and seasonal variations in the prevalence of acute viral hepatitis caused by hepatitis A virus.

Study Design: A descriptive study.

Place And Duration: The study was carried out on the patients reporting at Virology Department, Armed Forces Institute of Pathology (AFIP), Rawalpindi, for determination of hepatitis A virus (HAV) IgM antibody, from July 2003 to June 2004.

Patients And Methods: Altogether 626 patients with clinical suspicion of hepatitis A virus infection were referred to AFIP Rawalpindi for this test. Blood samples were collected and sera were separated and transferred to plastic aliquots that were stored at -20 degrees C in a retrievable fashion until utilized in testing. The testing for ant-HAV IgM was carried out with the help of a commercial Enzyme Linked Immunosorbant Assay (ELISA) using reagent kits of DiasSorin (Germany) for HAV IgM antibodies.

Results: The HAV IgM positive rate was 40.57% (252/626). Those tested included the sporadic cases as well as the patients from outbreak in two schools of Nowshera cantonment. The age of patients testing positive for HAV IgM, ranged from 03 to 27 years. There was a statistically significant seasonal difference in rate of positivity in different months of the calendar year. An outbreak of HAV infection was seen in the children of two neighboring schools of a cantonment, in which 44 children in different classes developed clinical jaundice.

Conclusion: HAV infection occurs in a significant proportion of young people with a clinical suspicion of HAV infection. There is a changing trend of developing hepatitis A in the age beyond 18 years and in outbreaks, which was not there in our patients previously due to universal immunity found against HAV by the age of 18. It was because of chances of consumption of polluted food.