Epidemic keratoconjunctivitis (EKC) or ‘‘shipyard eye’’ is an acute infectious disease of the eye. A case of EKC is defined as an illness

  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?