Makkah (Mecca) receives visitors from all over the world who often mix with immigrant residents of the same nationalities. This situation creates a danger of imported infectious diseases. For early detection and control of imported cholera, the Makkah health authorities culture stool or rectal swabs using TCBS agar from diarrhea patients presenting to hospitals. During April 1991 this surveillance system detected Vibrio cholerae O1 eltor Ogawa from both visitors from West African nations and resident immigrants from the same countries.
Methodology
We defined confirmed cholera as diarrhea with isolation of V. cholerae from stool or rectal swab. We extended surveillance to cover all diarrhea patients visiting Primary Health Care Centers (PHCCs) in the affected neighborhoods. We interviewed cholera patients about possible exposures and visited their homes to assess water source, sewage disposal and sanitation. We compared these data with a sanitation survey of houses in the same affected neighborhood.
Results
Surveillance detected 52 confirmed cholera cases, including 27 in Nigerians and other West Africans, from April through June 1991. The Hindawiyyah district had 53% (32) of the cases (AR 3.1/1000), distributed evenly by sex and age. Severity of illness and the case fatality ratio decreased after extending case detection to PHCCs (p<0.001; chi square for trend). In Hindawiyyah, none of the case houses were connected to the public sewage system, compared with 20% of survey houses (O.R.=0, p<0.05). Case houses were also more likely to have a pit latrine than the survey houses (O.R.=3.8; p<0.01). Only 3% of houses received piped municipal water. The remaining 97% used a variety of methods for water collection and storage, none of which alone was associated with illness. New cases ceased to be detected from Hindawiyyah one week after all household water supplies were chlorinated.
Conclusion
At the time of this outbreak, Nigeria was reporting cholera transmission. We suspect repeated importation of subclinical infection to Hindawiyyah district. Poor sanitation and drinking unchlorinated water contributed to the local spread in Hindawiyyah. Intensive surveillance through PHCCs was important in directing control measures toward high-incidence areas.