Assignment Week 3: OUTBREAK DETECTION

Assignment Week 3: OUTBREAK DETECTION

Assignment Week 3: OUTBREAK DETECTION

Tajikistan is one of five Central Asian countries that were formerly part of the Soviet Union (Figure 1). Tajikistan is one of the poorest of these countries, with less than 7% of its land available for cultivation.

Figure 1. Location of Tajikistan including the country’s capital and largest city, Dushanbe.

Tajikistan became an independent nation in 1991 as the result of the dissolution of the former Soviet Union. The shift in its status from being a member of a totalitarian republic to an independent nation brought with it certain challenges. Basic public services (e.g., health care, water supply, and sewer systems), previously guaranteed for even the poorest nations in the Soviet Union, were no longer supported through the Soviet cost-sharing system. Financial hardships and inadequate tariffs in Tajikistan severely limited provision of services and maintenance of equipment. Faulty design and installation of equipment while Tajikistan was still part of the Soviet Union added to these problems.

To make matters worse, shortly after becoming an independent nation, Tajikistan experienced a civil war that continued until a cease-fire occurred in 1996. During the civil war, an estimated 50,000 lives were lost and 1.2 million persons were internally displaced.3 In addition, a substantial number of trained technical and professional workers left the country.

By 1997, the country’s economy and much of its infrastructure had collapsed. Consequently, the health of the people of Tajikistan suffered. Diseases rarely seen before the dissolution of the Soviet Union reappeared in increasing numbers. Assignment Week 3: OUTBREAK DETECTION

Question 1: What health problems are common in countries with displaced populations, economic hardships, and deteriorating infrastructure?

Residents of Tajikistan received primary health care at designated polyclinics on the basis of their place of residence. The polyclinics provided ambulatory care and certain acute care services but lacked surgical and post-operative care facilities. Limited hospital beds at nationally run hospitals were available for patients needing in-patient services. Cases of notifiable disease were reported each week from the polyclinics and hospitals to the Sanitary Epidemiologic Service (SES), the public health unit that monitored infectious diseases.

In February 1997, an increase in typhoid fever cases was reported in Dushanbe, the capital of Tajikistan (population approximately 600,000). Although typhoid fever was endemic in this area, more than 2,000 cases had been reported during January 29−February 11 (i.e., a 2-week period), compared with approximately 75 cases each week during the previous month. During the same 2- week period in 1996, only 23 cases had been reported.

All typhoid fever patients were hospitalized at one of six full-service hospitals in the city, as required by a central government edict. SES staff studied the situation to determine the likelihood of an outbreak.

Question 2: Besides an outbreak, what are other possible explanations for the increase in cases of typhoid fever reported to the SES? How would you go about ruling out these other explanations?

As a first step in exploring the increase in typhoid fever cases in Tajikistan, SES investigators confirmed the diagnosis of typhoid fever in a sample of patients admitted to one of the Dushanbe hospitals. They also examined laboratory testing procedures and reagents at all six hospitals. No evidence of laboratory error or contamination of cultures was identified.

SES investigators were unable to identify recent events that might have led to an increase in the completeness of case reporting. Notifiable disease reporting procedures had not changed since the early 1980s.

SES investigators noted that the civil war had resulted in the displacement of substantial numbers of Tajikistan citizens and an increase in the Dushanbe population. However, movement of the displaced persons was spread over a lengthy period and seemed an unlikely explanation for the sudden increase in typhoid fever cases during January−February of 1997.

SES staff concluded that the increase in typhoid fever cases was real and likely represented an outbreak. Because previous typhoid fever outbreaks had been associated with foods and beverages sold by street vendors, the city government prohibited such sales. However, considerable debate remained about the source of the outbreak and appropriate control measures.

Question 3: How might you approach the development of hypotheses on the source of the typhoid fever outbreak?

PART II. HYPOTHESIS GENERATION
SES investigators pursued different lines of investigation to gain clues about the typhoid fever outbreak in Dushanbe. The first step was to review known information about the disease and risk factors on the basis of its epidemiology and previous outbreaks. Assignment Week 3: OUTBREAK DETECTION

Question 4: How is typhoid fever transmitted? What is the incubation period? (For additional information, see Appendix A.)

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