Cryptosporidiosis, 2013

During 2013, 324 cases of cryptosporidiosis (6.0 per 100,000 population) were reported. This is 19% higher than the median number of cases reported annually from 2003 to 2012 (median, 273 cases; range, 147 to 389). The median age of cases in 2013 was 26 years (range, 7 months to 89 years). Children 10 years of age or younger accounted for 23% of cases. Fifty-five percent of cases occurred during July through October. The incidence of cryptosporidiosis in the West Central, Southeastern, and Southwestern Districts (20.4, 17.0, and 14.6 cases per 100,000, respectively) was significantly higher than the statewide incidence. Only 60 (19%) reported cases occurred among residents of the metropolitan area (2.0 per 100,000). Forty-two (13%) cases required hospitalization, for a median of 4 days (range, 1 to 43 days).

Four outbreaks of cryptosporidiosis were identified in 2013, accounting for 17 laboratory-confirmed cases. One recreational water outbreak occurred at a municipal pool in Olmsted County, accounting for 10 cases (2 laboratory-confirmed). One outbreak associated with "Breakfast on a Farm" occurred, accounting for 2 primary cases and 1 secondary case, all laboratory-confirmed. One outbreak at a daycare in Douglas County accounted for 10 cases (6 laboratory-confirmed). An outbreak among HIV-infected men who had sex with men accounted for 6 laboratory-confirmed cases in 2013; 2 additional cases were identified in 2014.

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 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.

• For up to date information see>> Cryptosporidiosis (Cryptosporidium spp.)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2013