Three modes of transmission explain most giardiasis outbreaks

Three main modes of transmission have been identified for giardiasis outbreaks in the United States in 2012 to 2017, although a single transmission mode could not be identified for 43 percent of outbreaks, according to research published in the March 5 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Erin E. Conners, Ph.D., from the CDC in Atlanta, and colleagues characterized giardiasis outbreaks in the United States during 2012 to 2017. A total of 111 giardiasis outbreaks were reported to the National Outbreak Reporting System by public health officials from 26 states during 2012 to 2017.

The researchers identified three main modes of transmission for these outbreaks: water exposure, person-to-person contact, and contaminated food (26, 25, and 5 percent of outbreaks, respectively). In 43 percent of the outbreaks, a single transmission mode could not be determined. For all transmission modes combined, private residences and child care facilities were the most common settings of outbreaks.

“Results from this study suggest a need to focus prevention messages on the settings of giardiasis outbreaks, rather than on a single transmission mode,” the authors write. “In view of these results, giardiasis prevention and control initiatives and health materials should promote prompt diagnosis, maintaining good hand hygiene, cleaning and disinfecting home environments and child care facilities, and monitoring water quality in private wells.”