An unusual increase of Hepatitis A cases from Afif district, Riyadh region, was identified through surveillance in February 1997. A team from the Field epidemiology Training Program proceeded to Afif to estimate the extent of the outbreak and to identify its source and mode of transmission.
Methodology
We defined a Hepatitis A case as onset of jaundice between Jan. 1 and April 30, 1997, in a resident of Afif district. Affected families were interviewed about common exposure to other cases and common foods. The water source of 19 families having one or more cases were compared with the water source of 41 control-families without a case, from the same neighborhoods of Afif town.
Results
We detected 72 outbreak-associated cases of hepatitis A, including 47 in Afif town (attack rate [AR] = 18.5/10,000), 17 from rural villages (AR = 14.6/10,000) and eight from neighboring districts. Over two weeks, hepatitis A cases increased from a baseline of under one case per month to seven cases and averaged one case per week for the next 10 weeks. The 5- to 14-year-old age group had the highest AR (43/10,000). Interviews revealed no common exposure of affected families to other hepatitis A cases or common meals or eating-places. Afif water was brought in from up to 250 kilometers away and sold directly from trucks or through 10 commercial stations that sold both treated (filtered and chlorinated) and untreated water. All 19 case-families used untreated drinking water, compared with 24 (58%) control-families (p<0.01, Fisher's exact test). Seven (37%) case-families bought water directly from trucks, compared with only two (5 %) control-families (p< 0.01, Fisher's exact test); three (16%) bought water from trucks originating from Dahlah well in Qassim district, compared with none of the control-families (p<0.05, Fisher's exact test). Water from this well had been declared unfit for human consumption by Qassim district after several hepatitis A cases had occurred in a nearby village. Hepatitis A was not associated with any particular water station and the original water source for many included this suspect well. However, station records were insufficient to confirm the actual sources during the outbreak.
Conclusion
A common-source outbreak of Hepatitis A was transmitted through untreated drinking water, probably originating in a contaminated well in a neighboring district. Similar untreated water supplies are present in other areas of Saudi Arabia and represent a continuing threat to the public health.