Problem/condition: Cryptosporidiosis, a gastrointestinal illness, is caused by protozoa of the genus Cryptosporidium.
Reporting period: 2003-2005.
System description: State and two metropolitan health departments voluntarily reported cases of cryptosporidiosis through CDC's National Notifiable Diseases Surveillance System.
Results: During 2003--005, the total number of reported cases of cryptosporidiosis increased from 3,505 for 2003 to 3,911 for 2004 and to 8,269 for 2005. All reporting areas submitted reports, with more reports from northern states. Compared with other age groups, a greater number of case reports were received for children aged 1-9 years and adults aged 30-39 years. Peak onset of illness occurred annually during early summer through early fall.
Interpretation: Transmission of cryptosporidiosis occurs throughout the United States, with increased diagnosis or reporting occurring in northern states. An increase in cases reported for 2005 was attributable primarily to the occurrence of a single large recreational water-associated outbreak. State incidence figures should be compared with caution because individual state surveillance systems have varying capabilities to detect cases, and reporting might vary. The seasonal peak in age-specific case reports coincides with the summer recreational water season and might reflect increased use of communal swimming venues (e.g., lakes, rivers, swimming pools, and water parks) by young children.
Public health action: Cryptosporidiosis surveillance provides data to educate public health practitioners and health-care providers about the epidemiologic characteristics and the disease burden of cryptosporidiosis in the United States. These data are used to improve reporting of cases, plan prevention efforts, and establish research priorities.