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Key Clinical Updates in Viral Hemorrhagic Fevers

The World Health Organization recommends automated or semi-automated nucleic acid tests (NATs) of EDTA-anticoagulated whole blood from symptomatic patients for routine diagnostic management, and rapid antigen detection tests in areas where NATs are not available. Oral fluid can be used for diagnostics when blood collection is not possible.

Choi MJ et al. MMWR Recomm Rep. [PMID: 33417593]



  • Early-stage EVD: a nonspecific febrile illness.

  • Later stage EVD: severe GI symptoms, then neurologic symptoms and hypovolemic shock.

  • Hemorrhagic manifestations are late-stage manifestations.

  • Uveitis is prominent.

  • Travel and contact history from an Ebola-affected country raise suspicion.

  • Virus is detected via RT-PCR.

General Considerations

Genus Ebolavirus is a single-stranded RNA virus in the Filoviridae family. Four different species of Ebolavirus have been identified to cause human disease. Fruit bats are possible reservoirs for Ebolavirus. Zoonotic transmission to humans occurs via contact with the reservoir or an infected primate. Ebolavirus can continue to be transmitted among humans who have direct contact with infected body fluids. To acquire EVD, the virus must enter the body via mucous membranes, nonintact skin, sexual intercourse, breastfeeding, or needlesticks. Traditional burial practices in some African communities (which entail considerable contact with the corpse) and unprotected direct care of persons with EVD are associated with highest transmission risk. Ebolavirus has been detected in semen up to 9 months after recovery from infection.

EVD has a 2–21-day incubation period. Prior to manifestation of symptoms, Ebolavirus is not transmissible. Even at symptom onset, the risk of transmission is low but increases over time.

The first Ebola outbreak occurred in 1976 as a simultaneous epidemic in the Democratic Republic of Congo and South Sudan. Subsequent outbreaks were confined to the Democratic Republic of Congo, Uganda, and Sudan until March 2014 when the first Ebola case in West Africa was identified in Guinea. Zaire ebolavirus was the associated species. This Ebola outbreak grew to be larger than all prior Ebola outbreaks combined. The number of EVD cases spread rapidly; there were at least 10 affected countries, especially Guinea, Liberia, and Sierra Leone. Many cases and deaths in these countries occurred among health care workers. In the United States, 11 persons were treated for Ebola; most were health care workers who were evacuated to the United States, and four cases were diagnosed in the United States. In total, approximately 30 distinct outbreaks of Ebola have occurred since 1976, mostly in Africa. The estimated case fatality rate is 60%.

Sierra Leone contained its last EVD outbreak as of March 2016. Liberia declared the end of its last outbreak in June 2016. The WHO reports that the West African Ebola outbreak was associated with 28,616 cases and 11,310 deaths during the approximately 2-year interval of the outbreak between March 2014 and ...

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