Cryptosporidiosis, 2011

During 2011, 307 cases of cryptosporidiosis (5.8 per 100,000 population) were reported. This is 55% higher than the median number of cases reported annually from 1998 to 2010 (median, 198 cases; range, 91 to 389). The median age of cases in 2011 was 27 years (range, 3 months to 92 years). Children 10 years of age or younger accounted for 21% of cases. Fifty percent of cases occurred during July through October. The incidence of cryptosporidiosis in the Southwestern, Southeastern, West Central, and Northeastern districts (20.2, 17.8, 17.0, 11.5 cases per 100,000, respectively) was significantly higher than the statewide incidence. Only 47 (15%) reported cases occurred among residents of the metropolitan area (1.7 per 100,000). Fifty-two (17%) cases required hospitalization, for a median of 4 days (range, 2 to 66 days).

Three outbreaks of cryptosporidiosis were identified in 2011, accounting for 7 laboratory-confirmed cases. One recreational waterborne outbreak occurred among swimmers on a high school swim team, including 11 cases (2 laboratory-confirmed). One outbreak of cryptosporidiosis associated with drinking unpasteurized apple cider at an apple orchard where a petting zoo was present accounted for 4 cases (3 laboratory-confirmed). One outbreak at a daycare accounted for 2 cases (both laboratory confirmed).

In a paper published in Clinical Infectious Diseases in April 2010, we reported an evaluation of rapid assays used by Minnesota clinical laboratories for the diagnosis of cryptosporidiosis. The overall positive predictive value of the rapid assays was 56%, compared to 97% for nonrapid assays. The widespread use of rapid assays could be artificially contributing to the increased number of reported cases of cryptosporidiosis. Rapid assay-positive specimens should be confirmed with other methods. It is important that health care providers are aware of the limitations and proper use of rapid assays in the diagnosis of cryptosporidiosis and that they limit testing to patients who have symptoms characteristic of the disease cryptosporidiosis.

• For up to date information see>> Cryptosporidiosis (Cryptosporidium spp.)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2011