An outbreak of hepatitis A associated with treated waste water used for irrigation

Hepatitis A virus (HAV) infection is endemic in developing countries and remains a public health problem elsewhere. This study was conducted to investigate an outbreak of HAV infection, which occurred during a period of almost 5 months (January-May 1996) in the National Guard Iskan (Housing Authority) in Jeddah, Saudi Arabia. Ninety four cases were found to be positive for IgM antibody to HAV. A case control study was done to identify possible risk factors. For every case, 3 controls have been selected from the same household matched for age and sex. Information about reported cases was obtained by attending physicians through an interview questionnaire from adult cases and parents of young cases and controls (<12 y). It included questions regarding symptoms, demographics and possible source of the infection. Results showed that the attack rate of the whole population was 1.03 %, while that for children <10 years was twofold higher (2.05 %) than the total population. The risk of acquiring infection among them was found to be five times that among those aged 40 years and higher (R.R=5.32). There was a lack of association between developing hepatitis A and any of the food items or milk used in the studied area during the time of the outbreak. On the other hand exposure to irrigation water among cases was found to be significantly higher than among controls especially among children below 10 years (O.R=2.26). Analysis of the available data suggests a strong association between illness and exposure to waste water used for irrigation of gardens through playing with it, or through occasional drinking especially among children below 10 years. The prolonged course of the outbreak (5 months) may be attributed to subsequent person to person transmission from index cases to intimate contacts especially among the same household.