case studies X\XUnknown Disease in SC\Xunkdis_sc ... - Library

CDC / EIS Summer Course 2004: Epidemic Disease in S.C. - Student's Guide Page 2PART IOver a period of years, physicians in the ruralsoutheastern United States reported theoccurrence of a disease that had not beenrecognized previously. Since reporting wasrequired in only one state, and since medicalservices were limited, recording of the incidenceof this disease was irregular.Although the disease in question was easilydiagnosed on clinical grounds, the etiology wasunknown at the time. Pathogenesis, mode ofspread, immunity, and the role of social andenvironmental factors were matters ofcontroversy. Many theories concerning thenature of the disease were proposed.In an effort to determine the extent of thedisease, a questionnaire was mailed to allpracticing physicians in eight states in theSoutheast regarding the number of cases theyhad seen in the preceding 5 years. Onlyone-fourth of the physicians responded. Theyreported an increase from 622 to 7,017 casesover the 5-year interval.The following year, a U.S. Public Health Serviceepidemiologist was assigned to investigate theepidemic. After some preliminary observations,a field survey was conducted to determine theextent and the nature of the disease.Question 1:Into what general etiologic categories might one divide diseases that can occur inepidemic form?The survey was conducted in a five-countyregion in northwestern South Carolina where thedisease was prevalent. The survey areaincluded 24 mill towns with populations from 500to 1,500. These villages varied widely in theirsanitary status. Some had public water supplies,some had sewage systems, some had both, andsome had neither. The survey focused onfamilies of a single racial group.In each village, bi-weekly visits were made toeach household over a period of 1 year to lookfor cases. The name, age, sex, and maritalstatus of each member were recorded. Theoccurrence of the disease was determined byhistory and examination. Questionable caseswere referred to one of the directors of the studywho had considerable experience in diagnosingthe disease.Question 2:What categories of information would you want in order to describe the epidemic?