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  • More than 20 RNA viruses within the families Flaviviridae, Arenaviridae, Filoviridae, and the order Bunyavirales (previously family Bunyaviridae) cause hemorrhagic fevers (HFs).

  • The prevalent viral HFs (VHFs) are dengue, yellow fever (YF), Lassa fever (LF), Rift Valley fever (RVF), and hemorrhagic fever with renal syndrome (HFRS).

  • Ebola virus (EBOV) caused a major outbreak in West Africa during 2014-2016 that led to >11,000 deaths. Because of the unusually large size and longer duration of this epidemic, our understanding of the spectrum of Ebola virus disease has improved.

  • The major factors in Ebola transmission are infection of household contacts of symptomatic infected individuals and exposure to infection during traditional burial practices.

  • Hantaviruses cause HFRS in the Old World and hantavirus cardiopulmonary syndrome (HCPS) in the New World. HCPS manifests as low-pressure pulmonary edema, pleural effusions, and cardiogenic shock, but not HF.

  • Mosquitoes are the vector of dengue, YF, and RVF.

  • Ticks are the vector of Crimean-Congo HF (CCHF), Omsk HF (OHF), Kyasanur forest disease (KFD), Alkhurma HF, and severe fever with thrombocytopenia syndrome (SFTS).

  • Arenaviruses and hantaviruses are rodent-borne zoonoses.

  • Marburg virus reservoir is a cave-dwelling, fruit-eating bat, Rousettus aegyptiacus; Ebola virus reservoir is not confirmed, although tree-roosting, fruit-eating bats are suspected.

  • Exposure to domestic animals is a major mode of infection in RVF and CCHF.

  • RVF causes simultaneous epizootics in animals and large epidemics in humans. A small minority of infected persons develop HF, encephalitis, or retinitis.

  • Dengue and Seoul hantavirus are urban infections. YF is endemic in jungles and African savannas, but also causes urban epidemics. Ebola is usually a rural infection but has the potential to spread to urban centers. The other VHFs are mostly rural infections.

  • Health care–associated infections are a feature of CCHF, filoviruses, arenaviruses, Andes hantavirus, and SFTS virus.

  • Air travel can transport infected persons with VHF to nonendemic areas, including Europe and North America. Especially with Ebola, Marburg, and Lassa, there is a risk of health care–associated outbreaks even in a modern hospital with good adherence to standard infection control practices. Special precautions are required for patients with suspected HF.

  • The incubation period is shorter than 2 weeks in most infections. The incubation of Ebola ranges from 2 to 21 days. The incubation is longer with hantaviruses (10 days to 5 weeks). The onset of illness usually is sudden but is insidious with arenaviruses.

  • Clues to dengue fever are urban acquisition, break-bone fever, rash, hemoconcentration, and thrombocytopenia. Danger signs for severe dengue include abdominal pain, persistent vomiting, effusions, mucosal bleed, lethargy, restlessness, liver enlargement, hemoconcentration, and severe thrombocytopenia.

  • YF vaccine–associated viscerotropic disease (YEL-AVD) may rarely occur in persons who are older or have abnormal thymus function. YF vaccine is contraindicated in immunocompromised persons.

  • Clues to LF are insidious onset, sore throat, chest pain, cervicofacial edema, high maternal mortality and fetal loss during pregnancy, and irreversible sensorineural deafness.

  • Clues to filoviruses are fever, diarrhea, severe bleeding, jaundice, rash, person-to-person transmission in ...

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