MMWR Vol. 64 / No. SS-3 ► Giardiasis Surveillance — United States, 2011–2012

MMWR Vol. 64 / No. SS-3

MMWR Surveillance Summaries Vol. 64, No. SS-3 May 1, 2015

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Giardiasis Surveillance — United States, 2011–2012 
Painter JE, Gargano JW, Collier SA, et al.
MMWR Surveill Summ 2015;64(No. SS-3) 

Giardiasis is a nationally notifiable gastrointestinal illness 

caused by the protozoan parasite Giardia intestinalis. Forty-four 

states, the District of Columbia, New York City, the Commonwealth 

of Puerto Rico, and Guam voluntarily reported cases of giardiasis 

to CDC through the National Notifiable Diseases Surveillance System 

(NNDSS). For 2011, a total of 16,868 giardiasis cases 

(98.8% confirmed and 1.2% nonconfirmed) were reported; for 2012, 

a total of 15,223 cases (98.8% confirmed and 1.3% nonconfirmed) 

were reported. In 2011 and 2012, 1.5% and 1.3% of cases, respectively, 

were associated with a detected outbreak. For the first time in 10 years, 

giardiasis rates appear to be decreasing. Educational efforts to decrease 

exposure to unsafe drinking and recreational water and prevent person-to-person 

transmission have the potential to reduce giardiasis transmission.