West Nile virus

Centers for Disease Control and Prevention (CDC): arboviral diseases, neuroinvasive and non-neuroinvasive - 2015 case definition[28]Centers for Disease Control and Prevention. Arboviral diseases, neuroinvasive and non-neuroinvasive 2015 case definition. 2015 [internet publication]. https://ndc.services.cdc.gov/case-definitions/arboviral-diseases-neuroinvasive-and-non-neuroinvasive-2015

Clinical criteria

A clinically compatible case of arboviral disease is defined as follows.

• Neuroinvasive disease:

  • Meningitis, encephalitis, acute flaccid paralysis, or other acute signs of central or peripheral neurologic dysfunction, and

  • Absence of a more likely clinical explanation.

• Non-neuroinvasive disease:

  • Fever as reported by the patient or a healthcare provider; and

  • Absence of neuroinvasive disease; and

  • Absence of a more likely clinical explanation.

Laboratory criteria for diagnosis:

• Isolation of virus from, or demonstration of specific viral antigen or nucleic acid in, tissue, blood, cerebrospinal fluid (CSF), or other body fluid; or

• Four-fold or greater change in virus-specific quantitative antibody titers in paired sera; or

• Virus-specific IgM antibodies in serum with confirmatory virus-specific neutralizing antibodies in the same or a later specimen; or

• Virus-specific IgM antibodies in CSF or serum.

Case classified as probable when:

• Neuroinvasive disease meets the above clinical criteria for neuroinvasive disease and meets the laboratory criteria of virus-specific IgM antibodies in CSF or serum but with no other testing

• Non-neuroinvasive disease meets the above clinical criteria for non-neuroinvasive disease and the laboratory criteria of virus-specific IgM antibodies in serum but with no other testing.

Case classified as confirmed when:

• Neuroinvasive disease meets the above clinical criteria for neuroinvasive disease and one or more of the following laboratory criteria:

  • Isolation of virus from, or demonstration of specific viral antigen or nucleic acid in, tissue, blood, CSF, or other body fluid; or

  • Four-fold or greater change in virus-specific quantitative antibody titers in paired sera; or

  • Virus-specific IgM antibodies in serum with confirmatory virus-specific neutralizing antibodies in the same or a later specimen; or

  • Virus-specific IgM antibodies in CSF, with or without a reported pleocytosis, and a negative result for other IgM antibodies in CSF for arboviruses endemic to the region where exposure occurred.

• Non-neuroinvasive disease meets the above clinical criteria for non-neuroinvasive disease and one or more of the following laboratory criteria:

  • Isolation of virus from, or demonstration of specific viral antigen or nucleic acid in, tissue, blood, or other body fluid, excluding CSF; or

  • Four-fold or greater change in virus-specific quantitative antibody titers in paired sera; or

  • Virus-specific IgM antibodies in serum with confirmatory virus-specific neutralizing antibodies in the same or a later specimen.