A waterborne outbreak of gastroenteritis with secondary person-to-person spread. Association with a viral agent.

In December, 1976, an outbreak of gastroenteritis occurred at a resort camp in Colorado. Data obtained by questionnaire from 760 persons indicated that 418 (55%) had had gastroenteritis at the camp or within a week of leaving it, with peak onset within a two-day period. Symptoms included vomiting (81%), diarrhoea (65%), and fever (49%); median duration of illness was twenty-four hours. The attack-rate increased with consumption of water or ice-containing beverages. The camp water supply was found to be inadequately chlorinated and contaminated by a leaking septic tank. Although routine laboratory tests did not reveal bacterial, viral, or parasitic pathogens, immune electron microscopy detected virus-like particles in two of five diarrhoeal stool filtrates. Oral administration of one of these bacteria-free filtrates to two volunteers induced a gastrointestinal illness similar to that observed in the camp visitors.

Non-polio enterovirus disease in the United States, 1971--1975.

Reports to the Center for Disease Control on isolation of non-polio enteroviruses for the years 1971--1975 were analysed. During the 5 year period, enterovirus isolations were reported from 7 075 individuals. 90% of these occurred in the 7 month interval of May--November. Enteroviruses were isolated more frequently from males than females for all age groups in all 5 years. The incidence of reported isolations decreased with increasing age, and an inverse relationship between severity of disease and age was suggested. Clinical diagnoses associated with enteroviral isolations included aseptic meningitis, encephalitis, upper respiratory tract disease, non-specific febrile illness, gastroenteritis, pneumonia and lower respiratory tract disease, exanthem, and enanthem.

St. Louis encephalitis: the Chicago experience.

The largest laboratory-documented outbreak of St. Louis encephalitis (SLE) in the United States occurred in the Chicago metropolitan area in the summer and early fall of 1975. Of 1,456 illnesses investigated, 326 cases of confirmed or probable SLE and 420 cases of suspected SLE were found in the six-county area. The outbreak peaked in early September, but cases continued to occur through October. Cases clustered geographically in the southwestern suburbs. There was a direct correlation between age and attack rate, severity of illness, and mortality rate--all of which increased with successive age groups. Thirty-six persons died. Males and females were equally affected. This epidemic marked the first time that St. Louis encephalitis has been documented in the Chicago area.

Epidemic keratoconjunctivitis at a Vietnamese refugee camp in Florida.

During the summer of 1975 an ongoing outbreak of conjunctivitis occurred among Vietnamese refugees temporarily housed at a U.S. mainland camp. Twenty-two per cent of surveyed refugees gave a history of the disease and 10% were documented as having clinical conjunctivitis at the time of the survey. Fifty-six per cent of documented cases were in children less than 10 years of age. The attack rate among American camp personnel was 4%. Comprehensive microbiologic analysis revealed multiple potential pathogens in most cases, but the recovery of adenovirus 8 (AV8) in 81% of cases cultured within two weeks of onset implicated AV8 as the principal cause of the epidemic.

Lassa fever: response to an imported case.

In February, 1976, a Peace Corps worker returned to the United States from Sierra Leone with an undiagnosed illness later recognized as Lassa fever. To assess the risk of transmission and to contain a potential outbreak, we identified 552 contacts as having had exposure to the patient before the start of strict isolation procedures, and maintained intensive surveillance on these contacts for 21 days. At the end of the surveillance period, no illness had developed in contacts. One month later, a serologic survey among 29 of the contacts judged to be at high risk gave no evidence of infection. In response to the importation of this communicable and highly fatal disease, procedures for the isolation of the patient, the identification, surveillance and management of contacts and the handling of laboratory specimens were developed and implemented. These procedures could be adapted to future introductions of highly contagious diseases.