Generate a Differential Diagnosis

Differential Diagnosis

One of the most important initial steps when investigating an outbreak of unknown respiratory illness is generating the “differential diagnosis.” The differential diagnosis is a list of the most likely infectious causes or etiologies of an outbreak. Differential diagnosis also refers to the process of comparing how likely one pathogen caused the disease versus another.

Generating a differential diagnosis enables investigators to use time and resources most efficiently and effectively to determine an outbreak’s etiology. The process helps focus questionnaire development, specimen collection, laboratory testing, empiric treatment regimens, and targeted urgent public health interventions. Also, a thoughtful differential diagnosis ensures investigators consider all likely etiologies early in an outbreak investigation. This process makes it less likely that investigators miss or overlook an etiology.

Differential Diagnosis Spreadsheets

The spreadsheets below summarize information on the principle pathogens or groups of infectious agents known to cause respiratory illness. For each etiology, the spreadsheets summarize

  • Host demographics and epidemiologic features of infection
  • Clinical features of infection and disease control
  • Known risk factors for disease

Investigators should use all information or “clues” available throughout an unexplained respiratory outbreak to determine the most likely etiology.

Demographic and Epidemiologic Data Cdc-pdf[2 pages]

For each pathogen, this spreadsheet includes information on:

  • Incubation period
  • Means of disease transmission
  • Age groups most often affected
  • Case fatality rate
  • Geographic distribution, both in the United States and worldwide

Clinical Information Cdc-pdf[2 pages]

For each pathogen, this spreadsheet lists:

  • The predominant respiratory syndrome for each pathogen
  • Other clinical manifestations
  • Most common findings on chest x-ray
  • Unique laboratory findings
  • Unique pathology findings
  • Vaccine availability
  • General infection control precautions

Risk Factors for Disease Cdc-pdf[2 pages]

For each pathogen, this spreadsheet lists:

  • Specific group settings often affected
  • Specific occupations, animal and environmental exposures, or other activities that place a person at increased risk
  • People with increased susceptibility or disease severity
  • If there is potential use as a bioterrorism agent

Persons with disabilities having problems accessing the above files may call 1-800-CDC-INFO (1-800-232-4636) for assistance.