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Cases = 654

Crude rate (per 100,000 population) = 11.8

Age-adjusted race-specific rates (per 100,000 population)

White = 6.6
Nonwhite = 5.9

Gender-specific rates (per 100,000 population)

Female = 11.0
Male = 12.3

Giardiasis is a flagellate protozoan infection transmitted most commonly by ingestion of cysts in fecally contaminated water and by person-to-person, hand-to-mouth transfer of cysts from the feces of infected individuals.

There were 654 cases of giardiasis reported in 1999, which represents a decrease over the previous year (Figure 1). This was lower than the previous 5 year average incidence (832 cases/year).

Figure 1.

The number of reported cases was highest during the mid-summer and early autumn months (Figure 2). The increase during warm weather months may indicate increased exposure to contaminated surface water during outdoor activities.

Males (12.3) were more likely to be reported than females (11.0). Age-specific rates were highest among children aged one to four years (24.7) followed by children under age one (24.0), which highlights the increased risk of transmission in daycare centers (Figure 3). Nationally, outbreaks of giardiasis have been occurring more frequently in daycare centers. Transmission in daycare centers can be avoided through exclusion of children with diarrhea and good handwashing practices.

Figure 3.

Among counties with at least 5 cases reported, the incidence rates were highest in Steuben (36.4),

Wells (34.7), Marshall (28.5), Jasper (28.0) and Allen (26.2) counties (Figure 4).

There were no outbreaks of giardiasis reported in Indiana in 1999.

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