Giardiasis surveillance--United States, 2009-2010

Giardiasis is a nationally notifiable gastrointestinal illness caused by the protozoan parasite Giardia intestinalis.

2009-2010.

State, commonwealth, territorial, and two metropolitan health departments voluntarily report cases of giardiasis through CDC's National Notifiable Diseases Surveillance System.

During 2009-2010, the total number of reported cases of giardiasis increased slightly from 19,403 for 2009 to 19,888 for 2010. During this period, 50 jurisdictions reported giardiasis cases. A larger number of case reports were received for children aged 1-9 years than with other age groups. The number of cases peaked annually during early summer through early fall.

Transmission of giardiasis occurs throughout the United States, with more frequent diagnosis or reporting occurring in northern states. However, state incidence figures should be compared with caution because surveillance capacity differs between states. Giardiasis is reported more frequently in young children, which might reflect increased contact with contaminated water or ill persons.

Local and state health departments can use giardiasis surveillance data to better understand the epidemiologic characteristics and the disease burden of giardiasis in the United States, design efforts to prevent the spread of disease, and establish research priorities.