In January and February 1997, the Riyadh region surveillance identified an unusual increase of hepatitis A cases from Afif district. An epidemiologic investigation was initiated to estimate the extent and size of outbreak, and to identify its source and mode of transmission.
We defined a hepatitis A case as onset of jaundice between Jan. 1 and April 30, 1997, in a resident of Afif district. We interviewed affected families about contact with and food exposures common to other families with hepatitis A. We compared the water source of 19 families with one or more cases to the water source of 41 families without a case (control-families) selected from the same neighborhoods of Afif town.
Seventy-two cases of hepatitis A occurred during the outbreak period: 47 in Afif town (attack rate [AR] = 18.5/10,000), 17 from rural villages (AR = 14.5/10,000) and eight from neighboring districts. Over two weeks in late February 1997, hepatitis A cases increased from a baseline of under one case per month to 14 cases and averaged four cases per week for the next 10 weeks (Figure 1). The 5to-14-year age group had the highest AR (43/10,000). Interviews revealed no common exposure of affected families to other hepatitis A cases or to common meals or eating places.
Afif water was trucked in from surface rainwater collection and wells up to 250 kilometers distant. This water was sold directly from trucks or through 10 commercial stations. Six stations sold only untreated water (no chlorination), three sold both treated (filtered and chlorinated) and untreated water, and one sold only treated water. All 19 case-families used untreated drinking water, com-pared with 24 (58%) control-families (p<0.01, Fisher's exact test). Seven (37%) case-families bought untreated water directly from trucks, compared with only 2 (5%) control-families (p<0.01, Fisher's exact test), and three (16%) case-families bought water from trucks originating from the Dahlah well in the Qassim region, 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 the Qassim authorities after several hepatitis A cases had occurred in a nearby village. The original water source for many commercial water stations included this suspect well; however, station records were insufficient to verify the actual sources during the outbreak. Hepatitis A was not associated with any one water station in Afif Smaller concurrent outbreaks had occurred in Dwadmi along the road from Dahlah to Afif.
Editorial note:
Although hepatitis A is normally transmitted person-to-person and appears as a propagated pattern, point or common-source outbreaks have been associated with food, water and milk. This outbreak of hepatitis A occurred suddenly with a rapid rise in cases to a peak, thus suggesting a point or common-source outbreak. Interviews indicated that person-to-person spread was not responsible for transmission within the town.
This investigation was complicated by poor or non-existent records at the water stations showing the actual source of the water purchased from the trucks. Accordingly, the true source of the water for some of the stations may not have been correct. Individuals who bought water directly from tanker trucks did not know the actual source of the water. Only the truck driver knew for sure.
People need an adequate supply of safe drinking water. There are major problems in the water system in Afif town. It is a multi-source system and is not controlled or inspected by the government. Moreover, the drinking water supply systems in surrounding villages and towns could also be unsafe, providing water that is unfit for drinking.
The water system in Afif needs to be evaluated for adequacy, and the water treatment and monitoring of water quality needs to be regulated and inspected. Uncontrolled, non-chlorinated and unfiltered drinking water generalized the extent and the size of the problem in the surrounding areas, which have similar water supplies.
Many other microorganisms besides hepatitis A (cholera, Cryptosporidtum, Campylobacter spp, hepatitis E, viral gastroenteritis, Cyanobacteria, enterotoxogenic E. coli, enteroinvasive E. coli, Shigella, salmonella, Giardia lamblia, Entamoeba histolytica) may be transmitted by unsafe water. Health officials throughout Saudi Arabia need to be aware of the quality of their local drinking water supplies and to alert health authorities to possible deficiencies.
