title: Giardiasis surveillance--United States, 2009-2010.
abstract: OBJECTIVE
  Giardiasis is a nationally notifiable gastrointestinal illness caused by the protozoan parasite Giardia intestinalis.
  
  
  METHODS
  2009-2010.
  
  
  METHODS
  State, commonwealth, territorial, and two metropolitan health departments voluntarily report cases of giardiasis through CDC's National Notifiable Diseases Surveillance System.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Foodborne, Waterborne, and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, CDC. 1600 Clifton Rd, NE, Atlanta, GA 30333, USA. jyoder@cdc.gov
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Yoder
authors.forename: Julia W
authors.initials: JW
authors.lastname: Gargano
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Wallace
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Beach
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D016829:Giardia lamblia / Q000302:isolation & purification*; D005873:Giardiasis / Q000175:diagnosis / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D019221:Mandatory Reporting; D008875:Middle Aged; D011159:Population Surveillance; D012621:Seasons; D014481:United States / Q000453:epidemiology; D055815:Young Adult