Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to site content Skip directly to page options
CDC Home

Methodology - Case Definition and Ascertainment

Case Definition

To be considered a case for this surveillance system, the following case definition must be met:

  • Group A Streptococcus, group B Streptococcus, Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae or methicillin-resistant Staphylococcus aureus (MRSA) must be isolated from a normally sterile site, such as blood, cerebrospinal fluid (CSF), pleural fluid, peritoneal fluid, pericardial fluid, bone, joint/synovial fluid, or internal body site (e.g., lymph node, brain)
  • Case patient must be a resident of one of the defined surveillance areas

The following are exceptions to this sterile site case definition and would be counted as cases for this surveillance system:

  • Group B Streptococcus isolated from the placenta and/or amniotic fluid with fetal demise
  • Group A Streptococcus isolated from a wound culture and accompanied by necrotizing fasciitis or streptococcal toxic shock syndrome (STSS)

Case Ascertainment

ABCs case finding is both active and laboratory-based. Since isolation from a normally sterile site is essential to the case definition, microbiology laboratories in acute care hospitals and reference laboratories processing sterile site specimens for residents of the surveillance area are contacted regularly for case identification. In hospitals without computerized microbiology data, surveillance personnel call designated microbiology laboratory contacts regularly to identify new cases and request isolate submission. Where microbiology data are computerized, electronic line listings of all ABCs sterile site isolates are obtained on a monthly basis.

Images and logos on this website which are trademarked/copyrighted or used with permission of the trademark/copyright or logo holder are not in the public domain. These images and logos have been licensed for or used with permission in the materials provided on this website. The materials in the form presented on this website may be used without seeking further permission. Any other use of trademarked/copyrighted images or logos requires permission from the trademark/copyright holder...more

External Web Site Policy This graphic notice means that you are leaving an HHS Web site. For more information, please see the Exit Notification and Disclaimer policy.

Contact Us:
  • Centers for Disease Control and Prevention
    1600 Clifton Rd
    Atlanta, GA 30333
  • 800-CDC-INFO
    TTY: (888) 232-6348
    Contact CDC-INFO The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Road Atlanta, GA 30329-4027, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC–INFO
A-Z Index
  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #