A COCCIDIOIDOMYCOSIS OUTBREAK FOLLOWING THE NORTHRIDGE, CALIF, EARTHQUAKE

Objective.-To describe a coccidioidomycosis outbreak in Ventura County following the January 1994 earthquake, centered in Northridge, Calif, and to identify factors that increased the risk for acquiring acute c occidioidomycosis infection. Design.-Epidemic investigation, populatio n-based skin test survey, and case-control study. Setting.-Ventura Cou nty, California. Results.-In Ventura County, between January 24 and Ma rch 15, 1994, 203 outbreak-associated coccidioidomycosis cases, includ ing 3 fatalities, were identified (attack rate [AR], 30 cases per 100 000 population). The majority of cases (56%) and the highest AR (114 p er 100 000 population) occurred in the town of Simi Valley, a communit y located at the base of a mountain range that experienced numerous la ndslides associated with the earthquake. Disease onset for cases peake d 2 weeks after the earthquake. The AR was 2.8 times greater for perso ns 40 years of age and older than for younger persons (relative risk, 2.8; 95% confidence interval [CI], 2.1-3.7; P<.001). Environmental dat a indicated that large dust clouds, generated by landslides following the earthquake and strong aftershocks in the Santa Susana Mountains no rth of Simi Valley, were dispersed into nearby valleys by northeast wi nds. Simi Valley case-control study data indicated that physically bei ng in a dust cloud (odds ratio, 3.0; 95% CI, 1.6-5.4; P<.001) and time spent in a dust cloud (P<.001) significantly increased the risk for b eing diagnosed with acute coccidioidomycosis. Conclusions.-Both the lo cation and timing of cases strongly suggest that the coccidioidomycosi s outbreak in Ventura County was caused when arthrospores were spread in dust clouds generated by the earthquake. This is the first report o f a coccidioidomycosis outbreak following an earthquake. Public and ph ysician awareness, especially in endemic areas following similar dust cloud-generating events, may result in prevention and early recognitio n of acute coccidioidomycosis.