Viral Hemorrhagic Fever (VHF)
2022 Case Definition

Background

Viral hemorrhagic fevers (VHFs) refer to a group of illnesses that are caused by several families of viruses, including filoviruses (Ebola and Marburg viruses), Old World arenaviruses (Lassa and Lujo viruses), New World arenaviruses (e.g. Guanarito, Machupo, Junin, Sabia, and Chapare viruses), and Crimean Congo hemorrhagic fever virus. The Council of State and Territorial Epidemiologists (CSTE) position statement  21-ID-04 made three key updates to the previous 10-ID-19 position statement on VHFs: 1) modified the definition for fever from ≥40ºC to ≥38ºC/100.4ºF, 2) added Chapare virus, a re-emerging New World arenavirus, to those reportable under position statement 21-ID-04, and 3) amended the epidemiologic linkage criteria for exposure within the past 3 weeks to semen from a confirmed acute or clinically recovered case of VHF to remove the stipulated time period of exposure within 10 weeks of the VHF case’s onset of illness.

Clinical Criteria

An illness with acute onset of:

• Fever > 38°C/100.4°F

AND

• One or more of the following clinical findings:
  • severe headache
  • muscle pain
  • erythematous maculopapular rash on the trunk with fine desquamation 3–4 days after rash onset
  • vomiting
  • diarrhea
  • abdominal pain
  • bleeding not related to injury
  • thrombocytopenia
  • pharyngitis (Arenaviruses only)
  • proteinuria (Arenaviruses only)
  • retrosternal chest pain (Arenaviruses only)

Laboratory Criteria

Any one of the following:

• Detection of VHF* viral antigens in blood by enzyme-linked immunosorbent assay (ELISA).
• VHF viral isolation in cell culture for blood or tissues.
• Detection of VHF-specific genetic sequence by reverse transcription polymerase chain reaction  (RT-PCR) from blood or tissues.
• Detection of VHF viral antigens in tissues by immunohistochemistry.

*VHF refers to viral hemorrhagic fever caused by filoviruses (Ebola virus, Marburg virus), Old World arenaviruses (Lassa and Lujo viruses), New World arenaviruses (Guanarito, Machupo, Junin, Sabia, and Chapare viruses), or viruses in the Bunyaviridae family (Rift valley fever virus, Crimean-Congo hemorrhagic fever virus). Rift valley fever is not currently a national notifiable condition.

Epidemiologic Linkage

One or more of the following exposures within the 3 weeks before onset of symptoms:

• Contact with blood or other body fluids of a patient with VHF
• Residence in—or travel to—a VHF endemic area or area with active transmission
• Work in a laboratory that handles VHF specimens
• Work in a laboratory that handles bats, rodents, or primates from a VHF endemic area or area with active transmission
• Sexual exposure to semen from a confirmed acute or clinically recovered case of VHF

Criteria to Distinguish a New Case from an Existing Case

A new case of VHF should be enumerated only if not previously counted as a case of VHF caused by the same virus as determined by laboratory evidence.*

*Among the VHFs included in CSTE position statement 21-ID-04, reinfection with the same virus species has not been documented. There is a theoretical possibility that a VHF (ex. Ebola) survivor could be infected by a virus that causes one of the other VHFs included in CSTE position statement 21-ID-04 (ex. Lassa fever, Crimean-Congo hemorrhagic fever, etc.).

Suspect

Meets clinical criteria AND epidemiologic linkage criteria.

Confirmed

Meets laboratory criteria.

• Viral Hemorrhagic Fever (VHF) | 2025 Case Definition
• Viral Hemorrhagic Fever (VHF) | 2011 Case Definition
• Viral Hemorrhagic Fever (VHF) | 2010 Case Definition