Recurrent exposure to Histoplasma capsulatum in modern air-conditioned buildings.

BACKGROUND: Between 1989 and 1996, an epidemic of histoplasmosis occurred on a medical school campus. There had been numerous construction projects on the campus that involved previously wooded land and were adjacent to a large bird sanctuary. METHODS: We investigated the epidemic with active surveillance to detect cases, a histoplasmin skin-test survey, inspection of the air-filtration systems of the involved buildings, and cultures of soil samples. The investigation also included a simulation of entry into air-intakes of the buildings from spore sources by means of a wind-tunnel analysis of a model of the campus that used inert gas. After control procedures were instituted, sentinel population groups had follow-up with yearly serological tests. RESULTS: From 1989 through 1996, there were 29 cases of histoplasmosis that occurred among school employees. All cases with a defined onset began during periods of ongoing campus construction. Positivity rates for histoplasmin skin testing were higher among on-campus personnel (47%) than among off-campus employee control subjects (28%) (P<.001); the rates were highest in employees who worked on the upper floors of 2 research buildings. The air-handling units on the roofs of these buildings were not designed to exclude Histoplasma spores. The wind-tunnel experiment indicated that spores aerosolized in the bird sanctuary were not taken into campus buildings. CONCLUSIONS: The major sources of employee exposure to H. capsulatum spores were the construction sites. Low-level, recurrent exposures occurred over several years inside modern research buildings. This phenomenon, which has not been previously described, may play a role in the epidemiology of spore-transmitted diseases in urban settings.

Campers' diarrhea outbreak traced to water-sewage link

From June through September 1979, diarrheal illness occurred in an estimated 1,850 persons who had camped at a private campground in Arizona. Illness occured more frecuently among campers at that campground than among those in the adjacent State park. The same well served both the private and the State campgrounds as the source of drinking water, but that water was distributed to the two campgrounds through separate lines. Illness was significantly associated with drinking water at the campsite, drinking larger quantities of campsite water, and camping on the southwest side of the campground. Samples of the water collected from the system during January through June contained no coliform bacteria. However, all those samples had been collected from the State park only. Of the 11 water samples submitted for bacteriological analyses during the summer, 3 had high levels of bacteria. Excavation of the water system uncovered a direct cross connection between the potable water system and a sewage-effluent irrigation system. This outbreak calls attentions to the importance of designing, maintaining, and monitoring potable water systems properly, especially those proximate to wastewater re-use systems