Prevalence and Incidence of Giardia

Giardia: Rare Disease

Giardia is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health (NIH). This means that Giardia, or a subtype of Giardia, affects less than 200,000 people in the US population.

Incidence (annual) of Giardia:

16.29 per 100,000 in Canada 2000¹ ... see also overview of Giardia.

Incidence Rate:

approx 1 in 6,138 or 0.02% or 44,308 people in USA [Source statistic for calcuation: "16.29 per 100,000 in Canada 2000¹" -- see also general information about data sources]

Incidence extrapolations for USA for Giardia:

44,308 per year, 3,692 per month, 852 per week, 121 per day, 5 per hour, 0 per minute, 0 per second. [Source statistic for calculation: "16.29 per 100,000 in Canada 2000¹" -- see also general information about data sources]

Prevalance of Giardia:

The overall incidence of infection in the United States is estimated at 2% of the population. Giardiasis is the most frequent cause of non-bacterial diarrhea in North America. (Source: FDA Bad Bug Book) ... Giardiasis is more prevalent in children than in adults, possibly because many individuals seem to have a lasting immunity after infection. This organism is implicated in 25% of the cases of gastrointestinal disease and may be present asymptomatically. The overall incidence of infection in the United States is estimated at 2% of the population. (Source: FDA Bad Bug Book)

Outbreaks of Giardia:

Major outbreaks are associated with contaminated water systems that do not use sand filtration or have a defect in the filtration system.

MMWR 38(23):1989: In April 1988, the Albuquerque Environmental Health Department and the New Mexico Health and Environment Department investigated reports of giardiasis among members of a church youth group in Albuquerque. The first two members to be affected had onset of diarrhea on March 3 and 4, respectively; stool specimens from both were positive for Giardia lamblia cysts. These two persons had only church youth group activities in common.

MMWR 32(50):1983: On August 8, 1983, the Utah Department of Health was notified by the Tooele County Health Department (TCHD) of an outbreak of diarrheal illness in Tooele, Utah, possibly associated with a contaminated public water supply that resulted from flooding during Utah's spring thaw. Morbidity and Mortality Weekly Reports For more information on recent outbreaks see the CDC. (Source: FDA Bad Bug Book)

About prevalence and incidence statistics:

The term 'prevalence' of Giardia usually refers to the estimated population of people who are managing Giardia at any given time. The term 'incidence' of Giardia refers to the annual diagnosis rate, or the number of new cases of Giardia diagnosed each year. Hence, these two statistics types can differ: a short-lived disease like flu can have high annual incidence but low prevalence, but a life-long disease like diabetes has a low annual incidence but high prevalence. For more information see about prevalence and incidence statistics.

Footnotes:
1. Notifiable Diseases Online, PPHB, Canada, 2000

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