Viral hemorrhagic fevers (VHFs) are a group of viral infections caused by viruses from five different families: Arenaviridae, Bunyaviridae, Filoviridae, Flaviviridae, and Paramyxoviridae. The most well-known VHFs are Lassa fever, Hantavirus syndromes, Ebola virus disease, Dengue hemorrhagic fever, and yellow fever. Transmission of VHFs occurs via contact with their animal or insect reservoirs or vectors (e.g., rodents, mosquitoes, ticks). Human-to-human transmission is also possible, e.g., via bodily fluids. VHFs predominantly occur in tropical and subtropical regions. Clinical features of VHFs vary but often include an initial nonspecific flu-like illness that progresses to multisystem hemorrhage. VHFs are diagnosed via antibody detection (e.g., IgG, IgM), PCR, or immunohistochemistry. Treatment is typically supportive, but antivirals may be used in some cases (e.g., ribavirin in Lassa fever). Case fatality rates vary greatly between VHFs but can be up to 90%. Vaccines are licensed internationally for yellow fever only, so prevention primarily consists of infection control measures.
- Pathogens are enveloped RNA viruses from the following families:
|Overview of common viral hemorrhagic fevers|
|Family||Virus||Disease(s)||Geography||Transmission||Case fatality rate|
| || || || |
Hantaviruses (especially Sin Nombre virus for HCPS)
| || || || |
|Hemorrhagic fever with renal syndrome (HFRS)|| || |
|Nairoviridae||Crimean Congo hemorrhagic fever virus||Crimean-Congo hemorrhagic fever|| || || || |
|Phenuiviridae||Rift valley fever virus||Rift valley fever|| || || || |
Ebola virus disease
| || || |
|Marburg virus||Marburg hemorrhagic fever|| || || || || |
|Flaviviridae||Dengue hemorrhagic fever|| || || || |
|Yellow fever virus||Yellow fever|| || || || |
- Initial flu-like illness
- Severe VHF with bleeding diathesis: develops in a variable number of cases, depending on the causative pathogen
- Diagnosis of VHF during the early stages is difficult because the symptoms are nonspecific.
- If clinical and laboratory features are consistent with the condition, further studies should be conducted to confirm the diagnosis.
- A detailed travel history to endemic regions is essential!
- History of exposure to a potential source of infection (e.g., rodents, mosquitoes, ticks)
- General laboratory studies
- Generally performed by specialized reference laboratories; presumptive positive results must be confirmed by the CDC. 
- Serology: IgM and/or rising levels of IgG antibodies detected using enzyme-linked immunosorbent assay (ELISA) or other diagnostic assays 
- Reverse transcription-polymerase chain reaction (RT-PCR) 
- Immunohistochemistry 
- sepsis or other types of
- Q fever
- Rickettsial infection (e.g., Rocky Mountain spotted fever)
- Acute leukemia
- Idiopathic thrombocytopenic purpura
- Thrombotic thrombocytopenic purpura
The differential diagnoses listed here are not exhaustive.
- Supportive treatment
- Medical treatment: Ribavirin may be used in some cases (e.g., Lassa fever) 
- Avoid contact with blood, body fluids, or tissue from infected reservoirs or humans
- Avoid travel to endemic areas
- In suspected cases
- Immediate notification of local health authorities and the CDC of any suspected cases of VHF
- Strict isolation of infected patients and their contacts with disinfection and sterilization measures
- Wear appropriate personal protective equipment (e.g., impermeable gown, gloves, respiratory protection, rubber boots).
- Probable, suspected, or confirmed cases of VHFs are notifiable conditions to local and state health authorities, as well as the CDC National Notifiable Disease Surveillance System.
- Epidemiology: See “Overview of viral hemorrhagic fevers” above.
- History of rodent or rodent urine exposure (e.g., picnicking in a park)
- Prodromal/febrile phase (∼ 2–7 days upon onset of illness): clinical features of VHF (see above)
- Syndrome-specific features
- HCPS: Cardiopulmonary phase (∼ 2–7 days following prodromal/febrile phase) with lung infiltration (pulmonary edema) and, in severe cases, development of acute respiratory distress syndrome (ARDS)
- HFRS: group of clinical syndromes of occurring mainly in Europe and Asia 
Diagnostics: If clinical and laboratory features are consistent with the condition, further studies should be conducted to confirm the diagnosis.
- Laboratory studies
- Confirmatory studies 
- Management 
- Prognosis: See case fatality rate in “Overview of viral hemorrhagic fevers” above.