Cryptosporidiosis, 2010

During 2010, 389 confirmed cases of cryptosporidiosis (7.4 per 100,000 population) were reported. This is 97% higher than the median number of cases reported annually from 1998 to 2009 (median, 197.5 cases; range, 91 to 349). The median age of cases was 25 years (range, 6 months to 94 years). Children 10 years of age or younger accounted for 28% of cases. Fifty-eight percent of cases occurred during July through October. The incidence of cryptosporidiosis in the West Central, Southwestern, Southeastern, South Central, and Northeastern districts (20.5, 20.2, 19.6, 14.3, and 13.4 cases per 100,000, respectively) was significantly higher than the statewide incidence. Only 52 (13%) reported cases occurred among residents of the metropolitan area (1.8 per 100,000). Forty-five (12%) cases required hospitalization, for a median of 4 days (range, 2 to 12 days).

Four outbreaks of cryptosporidiosis were identified in 2010, accounting for 14 laboratory-confirmed cases. Two recreational waterborne outbreaks occurred, including 3 primary and 1 secondary case (all laboratory-confirmed) associated with a swimming beach, and 2 cases (both laboratory-confirmed) associated with a community aquatic center. One outbreak of cryptosporidiosis associated with a veterinary school obstetrics laboratory class accounted for 9 cases (4 laboratory confirmed), and one outbreak associated with raw milk consumption accounted for 4 cases (all laboratory-confirmed).

In a paper published in Clinical Infectious Diseases in April 2010, MDH 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 non-rapid 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.

Updated Monday, November 28, 2011 at 02:10PM