Hospital: Report by IDSS, facsimile, mail or phone
Lab: Report by IDSS, facsimile, mail or phone, send isolate to SHL - (319) 335-4500
Physician: Report by facsimile, mail or phone
Local Public Health Agency (LPHA): Report by IDSS, facsimile, mail or phone. Follow-up required
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure Fax: (515) 281-5698
Hemolytic uremic syndrome (HUS) is a syndrome of anemia, renal failure and low platelet count, for which there are several causes. Among children, the most common cause of HUS is infection with a Shiga toxin-producing organism, most commonly Escherichia coli O157:H7 or some other strain of enterohemorrhagic E. coli (EHEC). Shigella dysenteriae also produces Shiga toxin and HUS can also occur after infection with this organism.
Thrombotic thrombocytopenic purpura (TTP) is a disorder characterized by lesions in various organs that contain platelet clots, low platelet counts, and hemolytic anemia [due to breakdown of red blood cells (RBC)]. Tissue hypoxia resulting from these clots may cause organ damage, most frequently affecting the nervous system or kidney.
B. Clinical Description
HUS is an acute illness involving the renal system and blood clotting mechanisms. For HUS caused by infection with a Shiga toxin-producing organism, the syndrome will usually manifest itself within weeks after the onset of a diarrheal illness, which often includes bloody diarrhea. Worldwide approximately 2- 7% of cases of enterohemorrhagic E. coli (EHEC), such as E. coli O157:H7, develop HUS.
Thrombotic thrombocytopenic purpura (TTP) is another potential consequence of infection with a Shiga toxin-producing organism. TTP symptoms include hemolytic anemia and signs of intravascular hemolysis, low platelet count, diffuse and nonfocal neurologic findings, decreased renal function, and fever.
HUS is most commonly seen in children, whereas TTP is more commonly seen in adults.
Both syndromes can be fatal. Most cases of HUS, but few cases of TTP, follow an acute gastrointestinal illness (usually diarrhea). Only HUS or TTP that follows an acute diarrheal illness should be reported.
While cattle appear to be the most significant reservoir for E. coli O157:H7 and other EHEC strains, other animals, such as deer, are also known to carry these bacteria. In contrast, humans are the only known reservoir for Shigella dysenteriae.
D. Modes of Transmission
See the chapters on E. coli -pathogenic and Shigella for modes of transmission for each organism.
E. Incubation Period
Onset of HUS or TTP usually occurs within 3 weeks of the onset of diarrhea. Diarrhea may have resolved and the case may appear to be improving when the onset of HUS or TTP occurs. (For the incubation periods of the specific bacteria, refer to the chapters on E. coli -pathogenic and Shigella.)
F. Period of Communicability or Infectious Period
People with HUS or TTP rarely are infectious due to shedding E. coli or Shigella in their stool. (Refer to the chapters on each of these organisms for information on their infectious periods.) These illnesses usually do not appear until after the shedding period is over. Thus, at this time, stool specimens are negative.
HUS is seen worldwide and may occur in 2% - 7% of E. coli EHEC infections of children under 10 years of age. A bacterial pathogen is often not laboratory confirmed in cases of HUS, and therefore, the proportion of cases of HUS due to specific bacterial infections is difficult to ascertain. Cases of HUS have been attributed to several non-O157:H7 E. coli serotypes (e.g., other EHEC strains). Treatment with TMP-SMX, fluoroquinolones and other antibiotics may increase the risk of HUS and other complications.
Post diarrheal TTP is seen less frequently than HUS.
H. Bioterrorism Potential
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for HUS can be found at: www.cdc.gov/osels/ph_surveillance/nndss/phs/infdis.htm#top
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
American Academy of Pediatrics. 2006 Red Book: Report of the Committee on Infectious Diseases, 27th Edition. Illinois, American Academy of Pediatrics, 2006.
CDC Website. Escherichia coli O157:H7. www.cdc.gov/ecoli/
Heymann, D.L., ed., Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.
Centers for Disease Control and Prevention: www.cdc.gov/ecoli/general/index.html#what_shiga
Iowa Division of Inspections and Appeals, Food Inspections: www.state.ia.us/government/dia/index.html