During 2005, 1,241 cases of Giardia infection (24.2 per 100,000 population) were reported. This represents an 11% decrease from the 1,398 cases reported in 2004; however, this figure is greater than the median number of cases reported annually from 1996 through 2004 (median, 1,098 cases; range, 851 to 1,556). Of the total number of Giardia cases for 2005, 697 (56%) represented positive tests during routine screenings of recent immigrants and refugees.
The median age for all case-patients reported in 2005 was 11 years (range, 3 months to 91 years). The median age among non-immigrant cases was 34 years (range, 6 months to 91 years). As in previous years, cases were clustered among children less than 5 years of age (28%); only 11% of cases were over 50 years of age. Overall, 3% of case-patients were hospitalized; 8% of case-patients over 50 years of age were hospitalized. There was one outbreak of giardiasis in Minnesota in 2005; the outbreak (seven cases) occurred in a child daycare setting with person-to-person transmission.
MDH began systematically interviewing cases of giardiasis in January 2002 to better characterize the illness and evaluate potential risk factors for infection. In 2004, 75% of the non-immigrant cases were interviewed. The symptoms most commonly reported by case-patients included diarrhea (95%), fatigue (78%), abdominal pain (77%), gas or bloating (77%), weight loss (67%) and nausea (65%); less commonly reported symptoms included vomiting (38%), and fever (30%). The median duration of diarrhea was 22 days (range, 1 to 212 days).
Case-patients were interviewed about potential exposures during the 14 days prior to their illness onset. Forty-one percent of interviewed case-patients reported traveling prior to their onset. Among travelers, 46% reported travel outside the United States. Nineteen percent of case-patients reported camping or hiking prior to onset, and 41% reported swimming or entering water. Forty-five percent of adult case-patients reported having children in their households; 48% of those case-patients had children in diapers. Twenty-six percent of adults reported changing a diaper prior to onset. Among pediatric cases, 31% of interviewed parents reported that their child had contact with a childcare setting prior to and/or during illness.
Note: For up to date information see: Giardiasis (Giardia)