CertMedEd – Ebola Virus Overview

CertMedEd – Ebola Virus Overview

General

Ebola, Ebola virus disease, or Ebola hemorrhagic fever is a disease of humans and other primates caused by an ebolavirus.  Ebola was first identified in 1976 in Sudan and the Democratic Republic of the Congo.  West Africa’s current Ebola epidemic began in December 2013 and as of September 17, 2014 the CDC have reported nearly 6,000 suspected cases and nearly over 2,500 laboratory confirmed deaths there.  Nations with imported cases include: France, Germany, Switzerland, Spain, United Kingdom, and the United States.

2014_Ebola_virus_epidemic_in_West_Africa

Signs and symptoms

The following 2 types of exposure history are recognized:

  • Primary exposure – typically involves travel to or work in an Ebola-endemic area
  • Secondary exposure – refers to refers to human-to-human exposure (eg, medical caregivers, family caregivers, or persons who prepared deceased patients for burial), primate-to-human exposure (eg, animal care workers who provide care for primates), or persons who collect or prepare bush meat for human consumption

Physical findings depend on the stage of disease at the time of presentation. With African-derived Ebolavirus infection, there is an incubation period (typically 3-8 days in primary cases and slightly longer in secondary cases).

Early findings may include the following:

  • Fever
  • Pharyngitis
  • Severe constitutional signs and symptoms
  • Maculopapular rash (best seen in white patients)
  • Bilateral conjunctival injection

Later findings may include the following:

  • Expressionless facies
  • Bleeding from intravenous (IV) puncture sites and mucous membranes
  • Myocarditis and pulmonary edema
  • In terminally ill patients, tachypnea, hypotension, anuria, and coma

Symptoms_of_ebolaSurvivors of Ebola virus disease have developed the following late manifestations:

  • Myalgias
  • Asymmetric and migratory arthralgias
  • Headache
  • Fatigue
  • Bulimia
  • Amenorrhea
  • Hearing loss
  • Tinnitus
  • Unilateral orchitis
  • Suppurative parotitis

Diagnosis

Diagnostic studies that may be helpful include the following:

  • Basic blood tests – Complete blood count (CBC) with differential, bilirubin, liver enzymes, blood urea nitrogen (BUN), creatinine, pH
  • Studies for isolating the virus – Tissue culture (only to be performed in one of a few high-containment laboratories throughout the world), reverse-transcription polymerase chain reaction (RT-PCR) assay
  • Serologic testing – Enzyme-linked immunosorbent assay (ELISA) for antigens or for immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies
  • Other studies – Immunochemical testing of postmortem skin, electron microscopy

Management

General principles of care are as follows:

  • Supportive therapy with attention to intravascular volume, electrolytes, nutrition, and comfort care is of benefit to the patient
  • Such therapy must be administered with strict attention to barrier isolation; all body fluids contain infectious virions and should be handled with great care
  • No specific therapy is available that has demonstrated efficacy in the treatment of Ebola hemorrhagic fever
  • There are no commercially available Ebola vaccines; however, neutralizing antibodies have been studied that may be useful in vaccine development or as passive prophylactic agents

At present, no specific anti-Ebolavirus agents are available. Agents that have been studied for the treatment or prevention of Ebola virus disease include the following:

  • Ribavirin (possesses no demonstrable anti-Ebolavirus activity in vitro and has failed to protect Ebolavirus -infected primates)
  • Nucleoside analogue inhibitors of S-adenosylhomocysteine hydrolase (SAH)
  • Interferon beta
  • Horse- or goat-derived immune globulins
  • Human-derived convalescent immune globulin preparations
  • Recombinant human interferon alfa-2
  • Recombinant human monoclonal antibody against the envelope glycoprotein (GP) of Ebola virus
  • DNA vaccines expressing either envelope GP or nucleocapsid protein (NP) genes of Ebola virus
  • Activated protein C
  • Recombinant inhibitor of factor VIIa/tissue factor

The FDA has allowed two drugs, ZMapp and an RNA interference drug called TKM-Ebola, to be used in people infected with Ebola during the 2014 outbreak. BioCryst’s BCX4430 small molecule is undergoing further animal testing as a possible therapy in humans.

In those patients who do recover, recovery often requires months, and delays may be expected before full resumption of normal activities. Weight gain and return of strength are slow. Ebola virus continues to be present for many weeks after resolution of the clinical illness.

 


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