1.4 Epidemic keratoconjunctivitis (EKC) or ‘‘shipyard eye’’ is an acute
infectious disease of the eye. A case of EKC is defined as an illness:
Consisting of redness, tearing, and pain in one or both eyes for more
than three days’ duration
Diagnosed as EKC by an ophthalmologist
In late October 1977, one (physician A) of the two ophthalmologists
providing the majority of specialized eye care to the residents of a central
Georgia county (population 45,000) saw a 27-year-old nurse who had
returned from a vacation in Korea with severe EKC. She received
symptomatic therapy and was warned that her eye infection could
spread to others; nevertheless, numerous cases of an illness similar to
hers soon occurred in the patients and sta¤ of the nursing home (nursing
home A) where she worked (these people came to physician A for diag-
nosis and treatment). Table E1.4 provides the exposure history of 22
persons with EKC between October 27, 1977 and January 13, 1978
(when the outbreak stopped after proper control techniques were ini-
tiated). Nursing home B, included in this table, is the only other area
chronic-care facility. Compute and compare the proportions of cases
from the two nursing homes. What would be your conclusion?TABLE E1.4
Exposure Cohort Number Exposed Number of Cases
Nursing home A 64 16
Nursing home B 238 61.5 In August 1976, tuberculosis was diagnosed in a high school student
(index case) in Corinth, Mississippi. Subsequently, laboratory studies
revealed that the student’s disease was caused by drug-resistant tubercule
bacilli. An epidemiologic investigation was conducted at the high school.
Table E1.5 gives the rate of positive tuberculin reactions, determined for
various groups of students according to degree of exposure to the index
case.
TABLE E1.5
Exposure Level Number Tested Number Positive
High 129 63
Low 325 36(a) Compute and compare the proportions of positive cases for the two
exposure levels. What would be your conclusion?EXERCISES 35