Emergency Preparedness

Kern Medical Bioterrorism Response Guide Section 2-C-2 – Viral Hemorrhagic Fever

Bioterrorism Epidemiology All of the VHF viruses (except dengue virus) are infectious by aerosol and could conceivably be used by an adversary as a bioterrorism agent. Incubation Period The incubation period for each of the VHF varies from 5 – 42 days depending on the virus. Clinical Presentation The VHF syndrome develops to varying degrees in persons infected with these viruses and exposure does not necessarily result in clinical disease. The target organ is the vascula r bed and the dominant clinical features are generally a consequence of microvascular damage and changes in vascular permeability. Common presenting complaints include fever, myalgias, and prostration. On physical examination conjunctival injection, mild hypotension, flushing and petechial hemorrhages may be evident. The disease often progresses to shock and generalized mucous membrane hemorrhage accompanied by neurological, hematological and pulmonary manifestations. Renal insufficiency is proportional to cardiovascular compromise. Some of the clinical characteristics of the various VHF are variable as demonstrated in table 1. Diagnosis A detailed travel history and a high index of suspicion are essential in making the diagnosis of VHF. Patients with arenavirus and hantavirus may recall having seen rodents during the incubation period. Since these viruses are transmitted to humans by aerosolized excreta or environmental contamination, actual contact with the reservoir is not necessary. Large mosquito populations are common in areas where Rift Valley fever or flavavirus transmission occurs. Any patient presenting with VHF syndrome in the United States should be regarded as a possible bioterrorist event and reported to the local health officer immediately. VHF should be suspected in any patient presenting with severe febrile illness and evidence of vascular involvement (subnormal blood pressure, postural hypotension, petechiae, hemorrhagic diathesis, flushing of the face and chest, and non-dependent edema. Symptoms of additional organ involvement may include headache, photophobia, pharyngitis, cough, nausea, vomiting, diarrhea, constipation, abdominal pain, hyperesthesia, dizziness, confusion and tremor. Laboratory findings will vary from disease to disease. White blood cell counts may be normal or elevated. Thrombocytopenia is a component of most VHF, but to a varying extent. Platelet counts may be normal and platelet function tests may be required to

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