During 2002, 982 cases of Giardia infection (20.0 per 100,000 population) were reported. This represents a 7% decrease from the 1,061 cases reported in 2001 and is near the low end of the range of the annual number of cases reported from 1996 through 2001 (median, 1,149 cases; range, 971 to 1,556).
The median age of case-patients reported in 2002 was 30 years. As in previous years, cases were clustered among children less than 5 years of age (21%); only 15% of cases were over 50 years of age. This age distribution suggests a higher risk for transmission among young children and the adults who care for them. Overall, 6% of case-patients were hospitalized; 17% of case-patients over 50 years of age were hospitalized. No food-borne or water-borne outbreaks of giardiasis were reported in 2002.
MDH began systematically interviewing cases of giardiasis in January 2002 in order to better characterize the illness and evaluate potential risk factors for infection. Fifty-eight percent of cases were interviewed. The symptoms most commonly reported by case-patients included diarrhea (97%), fatigue (84%), gas or bloating (79%), abdominal pain (77%), and nausea (61%); less commonly reported symptoms included vomiting (36%) and chills or fever (27%).
Forty-one percent of interviewed cases reported traveling in the 10 days prior to their illness onset. Among case-patients who reported travel, 28% reported travel outside the U.S. Twenty percent of case-patients reported camping or hiking in the 10 days prior to illness onset, and 41% reported having gone swimming or entered water before their onset. Fiftyeight percent of adult case-patients reported having children in their households; 59% of those case-patients had children in diapers. Thirty-eight percent of adults reported changing a diaper within the 10 days before their onset. Among giardiasis cases in children, 41% of interviewed parents reported that their child had contact with a childcare setting in the period before and/or during illness.