Viral hemorrhagic fevers refer to clinical illnesses associated with fever and a bleeding diathesis caused by a virus belonging to the Filoviridae, Arenaviridae, Bunyaviridae, or Flaviviridae families.
Viral hemorrhagic fevers are contracted through the bite of an infected arthropod, via aerosol generated from infected rodent excreta, by ingestion of contaminated foods, or by direct contact with infected animal carcasses. Yellow fever is an exception; it is contracted through the bite of an infected mosquito. Rift Valley fever can also be contracted by mosquitoes in addition to the aforementioned modes. At present, the vectors or reservoirs for Ebola and Marburg viruses are not understood.
Except for members of the Flaviviridae family, which lack human-to-human transmission, viral hemorrhagic fevers are highly contagious and spread easily from person to person via inhalation of aerosolized particles, mucosal exposure, or physical contact with a patient or corpse. As such, viral hemorrhagic fevers are categorized as Category A bioterrorism agents due to their high infectivity rate and mortality rates, which can be as high as 90% (Ebola). The most likely mode of transmission in a bioterrorist attack would be by aerosol.
The incubation periods of these diseases range from 2 to 21 days with a prodrome of 1 week or less. Symptoms typically include fever, headache, malaise, arthralgia, myalgia, nausea, abdominal pain, and nonbloody diarrhea. Filoviruses and flaviviruses typically exhibit an abrupt onset, whereas arenaviruses are slower.
Early signs of infection include fever, hypotension, relative bradycardia, tachypnea, conjunctivitis, and pharyngitis. Some patients may have an accompanying rash. Petechiae, mucous membrane and conjunctival hemorrhage, hematuria, melena, and hematemesis may be indicators of a progressing hemorrhagic diathesis. Advanced stages may demonstrate central nervous system findings such as delirium, convulsions, or coma. Recovery may be complicated by fatigue, anorexia, cachexia, alopecia, and arthralgia. Sequelae include hearing or vision loss, impaired motor coordination, transverse myelitis, uveitis, pericarditis, orchitis, parotitis, and pancreatitis.
With the exception of yellow fever, there are no vaccines for the viral hemorrhagic fevers. All suspected cases should be immediately reported to state and local health departments. Practice strict infection control measures including airborne and contact precautions. It is recommended that clinicians use either an N-95 mask or a powered air-purifying respirator (PAPR) when caring for viral hemorrhagic fever patients.
Ebola – Fever, malaise, weakness, myalgia, headache, anorexia, and sore throat, followed by nausea and vomiting, diarrhea, and stomach pain. Patients may develop joint pain, chest pain, and cough. Red eyes are common, and patients may develop a petechial skin rash. Hiccups or difficulty breathing may occur. Internal and external bleeding may also be seen.
Marburg – Fever, chills, cough, sore throat, headache, weakness, myalgias, chest pain, prostration, conjunctivitis, petechiae, purpura, and hemorrhage. May progress to nausea, vomiting, diarrhea, abdominal pain, jaundice, pancreatitis, anorexia, photophobia, delirium, shock, liver failure, hemorrhaging, and multi-system dysfunction.
Lassa fever – Flushing of the face and trunk. Facial edema and neck swelling may also be seen as well as cervical adenopathy, axillary petechiae, and hemorrhages in the setting of a severe febrile illness.
New World arenavirus (eg, Bolivian hemorrhagic fever) – Facial and upper trunk flushing, conjunctival redness, and axillary petechiae accompanied by fever, dizziness, muscle / chest / back / abdominal pain, headache, sore throat, lymphadenopathy, vomiting, cough, and photophobia lasting about 7 days. May progress to include petechiae and/or vesicles on the back of the throat and facial edema, mucosal hemorrhaging, and pulmonary edema.
Rift Valley fever – Fever, headache, backache, generalized weakness, nausea, and vomiting, which may or may not be associated with partial or complete loss of vision and/or hemorrhage. In patients with disease that has developed into hemorrhagic fever, look for jaundice, purpura, gingival bleeding, bloody vomit, and rectal bleeding.
Yellow fever – Facial flushing, conjunctival redness, and prominent low back pain in conjunction with the sudden onset of a flu-like illness. Within days, jaundice and other signs of liver involvement as well as hemorrhaging may be seen in about 15% of patients.
Omsk hemorrhagic fever – Vesicles on soft palate, upper body flushing (no rash), conjunctival erythema, petechiae, mucosal bleeding, and gastrointestinal hemorrhage.
Kyasanur Forest disease – Sudden onset of fever, chills, headache, severe prostration, arthralgia, generalized lymphadenopathy, myalgia, and facial flushing, followed in 72 hours by nausea, vomiting, diarrhea, and hemorrhage. Skin petechiae may be noted.