Moving Ebola patients by plane

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Saturday, 2 August, 2014

Two US citizens infected with Ebola virus (EBOV) are to be brought home in a specially equiped plane carrying an Aeromedical Biological Containment Unit. They will be housed in a PC3 isolation unit inside a negative pressure unit. See the CNN report and watch the informative video.

People and other animals with Ebola virus disease (EVD) have virus in all secretions and excretions, including saliva, sputum, faeces, vomitus, urine, sweat, tears and blood. EBOV is not excreted before signs develop and the amount of virus excreted increases as the disease progresses, but antigen was gone from fluids by day 16 in patients who survived (Rowe et al 1999). So in the incubation period the risk of transmission is zero, but rises as EVD becomes more severe. In convalescent patients viral RNA was detected in semen for several months, but not by virus isolation in culture (Rowe et al 1999). There has been no cases of transmission of EBOV from convalescent patients.

EBOV spreads via direct contact with EBOV entering via mucous membranes or broken skin, or contact with the virus on fomites, or by droplet infection. In the laboratory situation EBOV also survives long enough in air to be spread by aerosol (Piercy et al 2010; Lever et al 2012). Experimentally, EBOV can also be transmitted to mice and non-human primates via aerosol (Reed et al 2011; Lever et al 2012; Twenhafel etal 2013). However, the aerosol route seems not to occur in outbreaks in humans. EBOV is a reasonably hardy virus able to survive for weeks in liquids and even when dried on plastic or glass (Piercy et al 2010).

Zaire EBOV, the cause of the West African outbreak, is experimentally more pathogenic than Sudan EBOV or Cote d'Ivore EBOV (Lever et al 2012). The current outbreak is due to a new strain of Zaire EBOV (Baize et al 2014). Of the species of Ebolavirus Zaire EBOV is the one that has shown the greatest amount of evolution since its isolation in the 1990s (Li & Chen 2014). As the human epidemic in West Africa continues it seems feasible that the strain will respond to selection pressure and adapt to transmitting between human hosts in an urban environment.

Literature cited:

Baize et al. Emergence of Zaire Ebola Virus Disease in Guinea - Preliminary Report. New England Journal of Medicine 2014 Apr 16. [Epub ahead of print].
Lever et al. Lethality and pathogenesis of airborne infection with filoviruses in A129 α/β -/- interferon receptor-deficient mice. Journal of Medical Microbiology 2012;61(Pt 1):8-15.
Li YH, Chen SP. Evolutionary history of Ebola virus. Epidemiology and Infection 2014;142(6):1138-1145.
Piercy TJ, Smither SJ, Steward JA, Eastaugh L, Lever MS. The survival of filoviruses in liquids, on solid substrates and in a dynamic aerosol. Journal of Applied Microbiology 2010;109(5):1531-1539.
Reed DS1, Lackemeyer MG, Garza NL, Sullivan LJ, Nichols DK. Aerosol exposure to Zaire ebolavirus in three nonhuman primate species: differences in disease course and clinical pathology. Microbes and Infection 2011;13(11):930-936.
Rowe et al. Clinical, virologic, and immunologic follow-up of convalescent Ebola hemorrhagic fever patients and their household contacts, Kikwit, Democratic Republic of the Congo. Commission de Lutte contre les Epidémies à Kikwit. Journal of Infectious Diseases 1999;179 Suppl 1:S28-35.
Smither SJ, Piercy TJ, Eastaugh L, Steward JA, Lever MS. An alternative method of measuring aerosol survival using spiders' webs and its use for the filoviruses. Journal of Virological Methods 2011t;177(1):123-127.
Twenhafel NA, Mattix ME, Johnson JC, Robinson CG, Pratt WD, Cashman KA, Wahl-Jensen V, Terry C, Olinger GG, Hensley LE, Honko AN. Pathology of experimental aerosol Zaire ebolavirus infection in rhesus macaques. Veterinary Pathology 2013;50(3):514-529

Posted by Rick Speare

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