An outbreak of dysentery occurred among residents of Barshash, in the Najran region of southwestern Saudi Arabia. The entire population of 5,683 were immigrants from south Yemen. We went to Barshash when two residents of Barshash developed dysentery while traveling to another city and Shigella dysenteriae type 1 was isolated. We found that the Barshash primary health care center (PHCC) had a number of dysentery cases that had not been reported.
Methodology
We defined a dysentery case as any well person who developed diarrhea with blood in the stool in Najran between January and June 1993. We reviewed admission, laboratory and emergency room logbooks in King Khalid Hospital in Najran and logbooks from Barshash and six other PHCCs. We designed a questionnaire covering housing conditions, personal hygiene, water supply and contacts. We visited 31 houses with cases and 31 control houses and interviewed the families.
Results
We detected 859 cases of dysentery in Barshash from January to June 1993 (attack rate/1,000=151.2). The number of cases reported per week ranged from eight in February to 111 in May. Sixty percent of the cases were male; 79% of the cases were under 13 years old, and the median age was 6 (SD=15.4). "S. dysenteriae" type 1 was isolated from six cases. The Barshash area is divided into seven squares, and attack rates per 1,000 by square ranged from 36 to 746. A case-control study showed a significant difference between houses with only one water tank for drinking and washing and houses with separate water tanks for drinking and washing (odds ratio=2.25; 95% confidence interval [CI]=1.02-5.02). Houses with children's stool in the yard around the toilet had an odds ratio of 10.43 (95% CI=1.16-238.54).
Conclusion
This outbreak appeared to be propagated from house to house. That higher attack rates occurred in some squares suggests that transmission had not yet extended to all areas of Barshash. Generally, harsh environmental conditions (warm and dry) do not favor survival of "Shigella" except where water is available. Because tank water is not chlorinated, "Shigella" deposited in water containers and on taps when washing after defecation could survive to be transmitted when drinking or washing from the same tap. The presence of human stool in the yards indicates the need for improved education in personal hygiene, especially among children.