Giardiasis 
Annual Summary of Reportable Diseases

• No outbreaks of giardiasis were identified in Minnesota in 2023. 

During 2023, 445 cases of Giardia infection (7.8 per 100,000 population) were reported. This represents a 26% decrease from the median number of cases reported annually from 2013 through 2022 (median, 599 cases; range, 388 to 656). Recent immigrants and refugees accounted for 11% of cases. An additional 16% of cases reported international travel in the three weeks prior to illness onset. Excluding recent immigrants and refugees, the median age of cases was 39 years (range, 5 months to 93 years). Seventeen percent of cases were less than 10 years of age, and 38% were greater than 50 years of age. Fifty-six percent of non-immigrant and refugee cases were male. Giardia infections had a summer/fall seasonality; 50% of non-immigrant and refugee cases occurred during July through October. Thirty-eight (9%) cases required hospitalization, for a median of 3 days (range, 1 to 10 days). No outbreaks of giardiasis were identified in Minnesota in 2023. 

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During 2022, 472 cases of Giardia infection (8.3 per 100,000 population) were reported. This represents a 24% decrease from the median number of cases reported annually from 2012 through 2021 (median, 623 cases; range, 416 to 656). Recent immigrants and refugees accounted for 17% of cases. An additional 13% of cases reported international travel in the 3 weeks prior to illness onset. Excluding recent immigrants and refugees, the median age of cases was 46 years (range, 1 to 90 years). Fourteen percent of cases were less than 10 years of age, and 43% were greater than 50 years of age. Fifty-six percent of non-immigrant and refugee cases were male. Giardia infections had a summer/fall seasonality; 51% of non-immigrant and refugee cases occurred during July through October. Twenty-five (5%) cases required hospitalization, for a median of 6 days (range, 1 to 43 days). One outbreak of giardiasis was identified in Minnesota, accounting for one-laboratory-confirmed case. The outbreak was associated with person-to-person transmission in a childcare setting.

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During 2021, 388 cases of Giardia infection (6.9 per 100,000 population) were reported. This represents a 38% decrease from the median number of cases reported annually from 2011 through 2020 (median, 629.5 cases; range, 416 to 692). Recent immigrants and refugees accounted for 6% of cases. An additional 8% of cases reported international travel in the 3 weeks prior to illness onset. Excluding recent immigrants and refugees, the median age of cases was 39 years (range, 5 months to 94 years). Eighteen percent of cases were less than 10 years of age, and 38% were more than 50 years of age. Fifty-six percent of non-immigrant and refugee cases were male. Giardia infections had a summer/fall seasonality; 47% of non-immigrant and refugee cases occurred during July through October. Twenty-eight (7%) cases required hospitalization, for a median of 4 days (range, 2 to 17 days). No outbreaks of giardiasis were identified.

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During 2020, 416 cases of Giardia infection (7.4 per 100,000) were reported. This represents a 39% decrease from the median number of cases reported annually from 2010 through 2019 (median, 638 cases; range, 508 to 846). Recent immigrants and refugees accounted for 2% of cases. An additional 4% of cases reported international travel in the 3 weeks prior to illness onset. Excluding recent immigrants and refugees, the median age of cases was 42 years (range, 3 months to 94 years). Sixteen percent of cases were <10 years of age, and 39% were >50 years of age. Fifty-three percent of non-immigrant and refugee cases were male. Giardia infections had a summer/ fall seasonality; 52% of non-immigrant and refugee cases occurred during July through October. Twenty-five (6%) cases required hospitalization, for a median of 3 days (range, 2 to 24 days). Three outbreaks were identified in Minnesota that accounted for 9 laboratory-confirmed cases. These outbreaks were associated with person-to-person transmission in child-care settings.

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In 2019, 577 cases of Giardia infection (10.3 per 100,000) were reported. This represents a 12% decrease from the median number of cases reported annually from 2009 through 2018 (median, 648 cases; range, 508 to 846). Recent immigrants and refugees accounted for 10% of cases. An additional 16% of cases reported international travel in the 3 weeks prior to illness onset. Excluding recent immigrants and refugees, the median age of cases was 34 years (range, 2 months to 92 years). Seventeen percent were <10 years of age, and 37% were >50 years of age. Fifty-seven percent of non-immigrant and refugee cases were male. Giardia infections had a summer/fall seasonality; 47% of non-immigrant and refugee cases occurred during July through October. Thirty-seven (6%) cases required hospitalization, for a median of 4 days (range, 1 to 39 days).

Two outbreaks were identified that accounted for 10 laboratory-confirmed cases. Both outbreaks were associated with person-to-person transmission in childcare settings.

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During 2018, 508 cases of Giardia infection (9.1 per 100,000) were reported. This represents a 22% decrease from the median number of cases reported annually from 2008 through 2017 (median, 654 cases; range, 620 to 846). Recent immigrants and refugees accounted for 8% of cases. An additional 15% of cases reported international travel in the 3 weeks prior to illness onset. Excluding recent immigrants and refugees, the median age of cases was 35 years (range, 7 months to 98 years). Eighteen percent were <10 years of age, and 30% were >50 years of age. Fifty-seven percent of non-immigrant and refugee cases were male. Giardia infections had a summer/fall seasonality; 48% of non-immigrant and refugee cases occurred during July through October. Thirty-eight (7%) cases required hospitalization, for a median of 4 days (range, 2 to 27 days). Seven outbreaks were identified in Minnesota that accounted for 16 laboratory-confirmed cases. Five outbreaks were associated with person-to-person transmission in child care settings. One outbreak was associated with consumption of surface water along a Lake Superior hiking trail, and one outbreak was associated with swimming at a beach. Additionally, six Minnesota residents were involved in two outbreaks associated with backcountry camping trips in states outside Minnesota.

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• Archive of Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health
  Archive of past summaries (years prior to 2023 are available as PDFs).