Cluster of pulmonary blastomycosis in a rural community: evidence for multiple high-risk environmental foci following a sustained period of diminished precipitation.

Much of our understanding of the epidemiologic features of infection with Blastomyces dermatitidis has come from cluster and outbreak investigations which have established the association of human disease with recreational pursuits and the presence of infectious microfoci in areas of moist soil with high organic content. This report describes the clustering of eight cases of pulmonary blastomycosis without an apparent common source exposure which occurred during a 90 day period in a 96 square mile area (population 4,450) within Oconto County, Wisconsin. We conclude that multiple high-risk environmental foci may have existed following a sustained five-year period of diminished precipitation in the cluster area. A case-control study which included family and community controls concluded that multiple earth-disturbing activities engaged in by case-patients was statistically associated with illness. Lymphocyte-proliferation assays of whole blood samples detected previously unrecognized infection with B. dermatititidis among five of 32 family controls.

Four strains of Escherichia coli O157:H7 isolated from patients during an outbreak of disease associated with ground beef: importance of evaluating multiple colonies from an outbreak-associated product.

This report describes the investigation of a ground-beef-associated outbreak that involved five genetically distinct patient strains of Escherichia coli O157:H7. Human and product isolates were evaluated by pulsed-field gel electrophoresis (PFGE) with two endonucleases. The multiple-strain etiology of this outbreak underscores the importance of isolating and evaluating multiple colonies from outbreak-related products and comparing two endonuclease PFGE patterns of all product and human isolates identified during outbreak periods. This investigation emphasizes the importance of interviewing all confirmed and suspected case patients during the outbreak period, regardless of the PFGE pattern of their isolate, to confirm or rule out an epidemiologic link to the outbreak.