D-List Superbugs: Ebola Virus

Introduction

In light of its recent media attention and the first suspected case of Ebola in my home country of Nigeria on July 20th this year, I thought why not write about it. I noted that outside of the Hot Zone and the term “hemorrhagic fevers” my knowledge of what the Ebola virus was and its clinical presentation was limited. I decided to use this opportunity to provide a snapshot of the virus to date.

Etiology

The Ebola is a (-)ssRNA  enveloped virus from the Filovirus Family along with the Marburg virus. Within the Ebola genera, there are 5 distinct species classified by geographical location, 4 of which originate from Africa and are deadly to humans. The virus is able to survive a few weeks within the human bloodstream with infectivity and symptoms attributed to the immunosuppressive effects of the virus’ glycoprotein. It’s a Biosafety level 4 agent, THE HIGHEST BIOSAFETY LEVEL OUT! However, it’s not transmitted or hasn’t been shown to be transmissible by air yet. So don’t be fooled. Its classification at such a high level is due to its mortality and similar morbidity to agents that are transmitted via air and research is needed to re-classify the virus.

Ebola was identified in 1976 with two simultaneous outbreaks in DRC and Gabon . The virus resurfaced in 1996 in Gabon, Africa spreading via direct contact in 1996. Infection control was accomplished through isolation and closure of exposed healthcare. During this time the risk of nosocomial spread was established and that the infection rate could be reduced tremendously through proper hygienic conditions. Clinical history and the lack of laboratory evidence suggest that aerosol transmission plays a limited if any role in infectivity. The high mortality of apes, chimps, and humans with infection gives high suspicion that humans are not the appropriate reservoir for Ebola. Isolation of reverse transcriptase PCR and detection of antibodies in isolated randomized populations makes bats the more accepted reservoir.

Clinical Manifestations

Incubation is about 7-10 days. Early manifestations: HA, Myalgias, and high fever – looks almost like meningitis followed by GI symptoms specifically severe diarrhea and CP w/ cough. Symptoms progress to a desquamating rash more prominent in light-skinned population that involves ALL surfaces around Days 5-7 ->  mouth, palms, skin, all. Bleeding is not always seen in infected patients but typically begins around the same time as the rash. Other symptoms documented are generalized swelling, hepatomegaly, conjunctivitis, pharyngitis. Around Day 12 the fever breaks and symptoms begin to improve. So the key in treatment is to get the patient to survive the first week or so and provide supportive care so that the body can fight off the infection itself. For a lack of better words it’s pretty much downhill from there.

Labs: Leukopenia and thrombocytopenia => DIC picture. Kidney damage secondary to shock shows proteinuria with elevated creatinine and abd pain is associated with elevated AST > ALT and increased lipase.

Diagnosis

ELISA, PCR, Serum and semen antibodies

Treatment

No antiviral currently and symptomatic treatment has not shown to decrease morbidity or mortality.

Hopes: Factor VIIa/Tissue Factor or Activated Protein C has shown some promise suggesting DIC control to be important in the pathogenesis of Ebola virus. Prophylaxis using small interfering RNA (siRNA) has been listed. Be wary with extensive fluid resuscitation because the patient has increased vascular permeability and third-spacing is a well-documented problem leading to pulmonary edema, anasarca, and cardiac compromise

Still in development is the Adenovirus Vector Ebola glycoprotein gene and utilization of the Vesicular stomatitis virus based vaccine. Treatments targeting antithrombotic activity like   Recombinant nematode anticoagulant protein c2 (rNAPc2) inhibiting the FVIIa/tissue factor complex.

References

  1. Peters CJ. Chapter 197. Ebola and Marburg Viruses. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson J, Loscalzo J. eds. Harrison’s Principles of Internal Medicine, 18e. New York, NY: McGraw-Hill; 2012.
  2. Doucleff, Michaeleen. “2 Americans Catch Ebola in Liberia, As Nigeria Reports First Case”. http://www.npr.org/blogs/goatsandsoda/2014/07/28/336043452/2-americans-catch-ebola-in-liberia-as-nigeria-reports-first-case. July 2014.
  3. Ebola Virus Disease, West Africa – Update 25 July 25th: http://www.afro.who.int/en/clusters-a-programmes/dpc/epidemic-a-pandemic-alert-and-response/outbreak-news/4233-ebola-virus-disease-west-africa-25-july-2014.html.
  4. Laboratory Biosafety Level Criteria http://www.cdc.gov/biosafety/publications/bmbl5/bmbl5_sect_iv.pdf.
  5. http://www.samaritanspurse.org/

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