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Ebola Virus Disease and Hemorrhagic Fevers
Hemorrhagic Fevers
Overview and Transmission
Hemorrhagic fevers are caused by infection with single-stranded, small RNA viruses in the Arenaviridae, Filoviridae, Bunyaviridae, or Flaviviridae families ( Table 28.1 ). The clinical picture is usually one of hemodynamic instability and coagulation abnormalities leading to bleeding.
TABLE 28.1
Hemorrhagic Fever Viruses in Humans
Adapted from Bausch, D.G., 2011. Viral hemorrhagic fevers. In: Goldman's Cecil Medicine, twenty-fourth ed. Saunders Elsevier, Philadelphia, pp. 2147–2155.
| Family | Virus | Disease | Main Reservoir or Vector | Geographic Distribution of Disease |
|---|---|---|---|---|
| Arenaviridae | Lassa | Lassa fever | Rodent (multimammate rat, or Mastomys natalensis ) | West Africa |
| Lujo | Lujo hemorrhagic fever | Unknown; presumed rodent | Zambia | |
| Junin | Argentine hemorrhagic fever | Rodent (corn mouse, or Calomys musculinus ) | Argentine Pampas | |
| Machupo | Bolivian hemorrhagic fever | Rodent (large vesper mouse, or Calomys callosus ) | Beni Department, Bolivia | |
| Guanarito | Venezuelan hemorrhagic fever | Rodent (cane mouse, or Zygodontomys brevicauda ) | Portuguesa State, Venezuela | |
| Sabiá | Brazilian hemorrhagic fever | Unknown; presumed rodent | Rural area near São Paulo, Brazil? | |
| Chapare | Chapare hemorrhagic fever | Unknown; presumed rodent | Cochabamba, Bolivia | |
| Filoviridae | Ebola | Ebola hemorrhagic fever | Unknown; fruit and insectivorous bat species have been implicated | Sub-Saharan Africa |
| Marburg | Marburg hemorrhagic fever | Fruit bat (Egyptian fruit bat, or Rousettus aegyptiacus ; perhaps others) | Sub-Saharan Africa | |
| Bunyaviridae | Hantaan, Seoul, Puumala, Dobrava-Belgrade, others | Hemorrhagic fever with renal syndrome | Rodent (Hantaan: striped field mouse, or Apodemus agrarius ; Seoul: Norway rat, or Rattus norvegicus ; Puumala: bank vole, or Clethrionomys glareolus ; Dobrava-Belgrade: yellow-necked field mouse, or Apodemus flavicollis ) | Hantaan: northeast Asia Seoul: urban areas worldwide Puumala and Dobrava-Belgrade: Europe |
| Sin Nombre, Andes, Laguna Negra, others | Hantavirus pulmonary syndrome | Rodent (Sin Nombre: deer mouse, or Peromyscus maniculatus ; Andes: long-tailed rat, or Oligoryzomys longicaudatus ; Laguna Negra: vesper mouse, or Calomys laucha ) | Sin Nombre: North America, Andes Laguna Negra: southern South America |
|
| Rift Valley fever | Rift Valley fever | Domestic livestock/mosquito ( Aedes and others) | Sub-Saharan Africa, Saudi Arabia, Yemen | |
| Congo-Crimean hemorrhagic fever | Congo-Crimean hemorrhagic fever | Wild and domestic vertebrates/tick (primarily Hyalomma species) | Africa, Balkans, southern Russia, Middle East, India, Pakistan, Afghanistan, western China | |
| Flaviviridae | Yellow fever | Yellow fever | Monkey/mosquito ( Aedes aegypti , other Aedes and Haemagogus spp.) | Sub-Saharan Africa, South America up to Panama |
| Dengue | Dengue hemorrhagic fever | Human/mosquito ( A. aegypti and Aedes albopictus ) | Tropics and subtropics worldwide | |
| Kyasanur Forest disease | Kyasanur Forest disease | Vertebrate (rodents, bats, birds, monkeys, others)/tick ( Haemaphysalis species and others) | Southern India; Yunnan Province, China; Saudi Arabia | |
| Omsk hemorrhagic fever | Omsk hemorrhagic fever | Rodent/tick (primarily Dermacentor and Ixodes species) | Western Siberia |
The viruses are primarily zoonotic, existing in mammalian reservoirs. Humans may become infected by interaction with the reservoir or via an arthropod vector. While human-to-human transmission may occur with certain viruses and contribute to epidemics (with the exception of dengue), humans are not considered reservoirs. Therefore, infection primarily occurs in geographic locales that support the reservoir or the vector. However, all inhabited continents and climates host these viruses ( Table 28.1 ). In light of the recent epidemic of Ebola virus disease (EVD), special attention is given to this infection below. Yellow fever and dengue are discussed in other chapters.
Clinical Manifestations
The many different viruses that cause viral hemorrhagic fever (VHF) can result in a variety of clinical presentations. Early disease or mild infection can be nonspecific and potentially confused with respiratory viruses, hepatitis, gastroenteritis, primary human immunodeficiency virus, malaria, sleeping sickness, bacterial sepsis, or other infections. A variety of types of rash may be seen. In Lassa fever, the pharynx may be erythematous or exudative. Bleeding may not be overt and may be delayed; however, more severe disease may be characterized by bleeding, capillary leak, or shock. Laboratory findings may be variable but are often suggestive of disseminated intravascular coagulopathy. In severe disease, there may be pronounced electrolyte and acid-base disturbances.
Diagnosis
A high level of clinical suspicion for VHF in individuals who may have been exposed to reservoirs or vectors of infection is required. Confirmation of infection generally requires detection of viral antigen or RNA. These tests are performed in specialized laboratories; commercial kits for diagnosis are not currently available. Serology may be useful in the convalescent phase of illness. It is important to exclude other causes of infection.
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