Elham Reshid and Hailemariam Shimelis : Click for the PDF version

Ebola virus is an aggressive pathogen that causes a highly lethal hemorrhagic fever syndrome in humans and nonhuman primates. First recognized near the Ebola River valley during an outbreak in Zaire in 1976, outbreaks have occurred in Africa in the ensuing 27 years, with mortality rates ranging from 50 to 90%. The virus family Filoviridae includes 3 genera: Cuevavirus, Marburgvirus, and Ebolavirus. There are 5 species that have been identified: Zaire, Bundibugyo, Sudan, Reston and Taï Forest. The first 3 have been associated with large outbreaks in Africa. However, the virus causing the 2014 West African outbreak belongs to the Zaire species.

The infection is known to result in coagulation abnormalities, including gastrointestinal bleeding, development of rash, cytokine release, damage to the liver and massive viremia that leads to damaged vascular cells damage. As the massive viremia continues, coagulation factors are compromised and the microvascular endothelial cells are damaged or destroyed, resulting in diffuse bleeding internally and externally (bleeding from the mucosal surfaces like nasal passages and/or mouth and gums and even from the eyes [termed conjunctival bleeding]). This uncontrolled bleeding leads to blood and fluid loss, which in turn cause hypotensive shock and eventually death in many Ebola-infected patients.

The fact that the natural host for Ebola virus is unknown made it impossible to implement programs to control or eliminate viral reservoirs of transmission to human populations so far. Plus, the rapid progression of Ebola virus infection has further complicated the control of this disease, affording little opportunity to develop acquired immunity. There is currently no antiviral therapy or vaccine that is effective against Ebola virus infection in humans. However, a range of potential treatments including blood products, immune therapies and drug therapies are currently being evaluated. No licensed vaccines are available yet, but 2 potential vaccines are undergoing human safety testing.

Despite the treatment, important questions about this disease are not yet clearly answered. According to the suggestions made from the meeting held by The National Academies’ Institute of Medicine, it was mentioned that viral penetration through intact skin has not been definitively ruled out and the question of whether or not bleach or hand sanitizer makes the skin more susceptible to be penetrated by the virus is simply not known.

In addition, experts don’t know what the infectious dose of the virus is or if the dose size depends on where the virus enters the body. The incubation period and fever were another question to be raised. Is 21 days the outer limit of the incubation period for Ebola infection to occur? Although health officials emphasize that Ebola-infected people can only become able to transmit or shed Ebola viruses when they have a fever of at least 100.4 F (380C), it was stated that it is not definitively known at what temperature patients start shedding virus.



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