EBOLA AND MARBURG VIRUS INFECTIONS

MICROBIOLOGY

The family Filoviridae contains two genera, Marburgvirus and Ebolavirus, that consist of negative-sense, single-strand RNA viruses capable of infecting humans. Ebolavirus has five species named for their original sites of recognition, and Marburgvirus has two species.

  • Both Marburg virus and Ebola virus are biosafety level 4 pathogens because of high mortality rates (except for Reston virus, an Ebola virus, which is nonpathogenic for humans) and aerosol infectivity.

EPIDEMIOLOGY

  • Filoviruses pathogenic for humans are exclusively endemic to Equatorial Africa.
  • As of October 2017, there had been 31,602 human filovirus infections and 13,350 deaths (mortality rate, 41.7%), the overwhelming majority of which occurred during an outbreak in 2014–2015.
  • Since the discovery of filoviruses in 1967, there have been ∼50 natural host-to-human spillover events. Bats are thought to be the reservoir for Marburg and Ebola viruses.
  • Human-to-human transmission occurs through direct contact or exposure to infected bodily fluids and tissues; there is no evidence of such transmission by aerosol or respiratory droplets.

PATHOGENESIS

The pathogenic hallmarks of filovirus infection include pronounced suppression of the immune system, severe disturbance of the clotting system, and impairment of vascular integrity. Although petechiae, ecchymoses, and other hemorrhagic signs are detected in internal organs, mucous membranes, and skin, actual severe blood loss is a rare event.

CLINICAL MANIFESTATIONS

After a 3- to 25-day incubation period, pts develop a biphasic syndrome with a 1- to 2-day relative remission separating the two phases.

  • The first phase lasts 5–7 days and is characterized by an abrupt onset of fever, chills, severe headache, cough, myalgia, pharyngitis, and arthralgia and the development of a maculopapular rash.
  • The second phase involves the GI tract (e.g., abdominal pain, vomiting, diarrhea), respiratory tract (e.g., chest pain, cough), vascular system (e.g., postural hypotension, edema), CNS (e.g., confusion, headache, coma), and hemorrhagic manifestations.
  • Early leukopenia followed by leukocytosis with a left shift, thrombocytopenia, elevated levels of liver enzymes, and prolonged coagulation is common.
  • Pts typically die 4–14 days after infection. Survivors may have prolonged and incapacitating sequelae (e.g., arthralgia, asthenia, iridocyclitis, hearing loss, psychosis, transverse myelitis).
  • Filoviruses can persist in the liver, eyes, or testicles of survivors for months after convalescence and can be reactivated (causing recurrent disease) or transmitted sexually.

DIAGNOSIS

High concentrations of virus in blood can be documented by antigen-capture ELISA, virus isolation, or RT-PCR. Other diagnoses that must be excluded (as they closely mimic infection with Ebola or Marburg virus) include other VHFs (particularly yellow fever), falciparum malaria, typhoid fever, and gram-negative septicemia.

Treatment: Ebola and Marburg Virus Infections

  • Any treatment must be administered under increased safety precautions by experienced specialists using appropriate personal protective equipment (e.g., gowns, gloves, shoe covers, face shields) to prevent further transmission.
  • Treatment of filovirus infections is entirely supportive as no efficacious virus-specific therapy is available.
  • Several experimental therapies, including a monoclonal antibody cocktail (ZMapp) and vaccines, are currently being evaluated and have demonstrated some promise in small-scale studies.

Outline

EBOLA AND MARBURG VIRUS INFECTIONSis the Harrison's Manual of Medicine Word of the day!