Giardiasis, 2003

During 2003, 851 cases of Giardia infection (17 per 100,000 population) were reported. This represents a 13% decrease from the 982 cases reported in 2002 and is substantially less than
the annual number of cases reported from 1996 through 2002 (median, 1,098 cases; range, 982 to 1,556).

The median age of case-patients reported in 2003 was 25 years. As in previous years, cases were clustered among children less than 5 years of age (21%); only 16% 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; 19% of case-patients over 50 years of age were hospitalized.

There were two outbreaks of giardiasis in Minnesota in 2003; both occurred in child daycare settings (six and three confirmed cases, respectively) with person-to-person transmission. One waterborne outbreak was documented among Minnesota residents who were exposed to contaminated drinking water while camping in a national park in another state; 18 laboratory-confirmed cases among Minnesota residents were identified.

MDH began systematically interviewing cases of giardiasis in January 2002 in order to better characterize the illness and evaluate potential risk factors for infection. Sixty-two percent of the 2003 cases were interviewed. The symptoms most commonly reported by case-patients included diarrhea (95%), fatigue (82%), gas or bloating (74%), abdominal pain (73%), and nausea (62%); less commonly reported symptoms included vomiting (35%), and chills or fever (24%). The median duration of symptoms was 23 days (range, 2 to 358 days).

Case-patients were interviewed about potential exposures during the 14-day period prior to their illness onset. Forty-one percent of interviewed cases reported traveling prior to their onset. Among travelers, 25% reported travel outside the United States. Eighteen percent of case-patients reported camping or hiking prior to onset, and 39% reported swimming or entering water. Fifty-one percent of adult case-patients reported having children in their households; 53% of those case-patients had children in diapers. Thirtyfive percent of adults reported changing a diaper prior to onset. Among pediatric giardiasis cases, 42% of interviewed parents reported that their child had contact with a childcare setting prior to and/or during illness.

• For up to date information see>> Giardiasis (Giardia)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2003