Filoviridae

Marburg Virus Disease (MVD)

  • August 1967: 25 workers at an antiserum factory presented with sickness.

    • Symptoms: fever, headache, nausea/vomiting, malaise, myalgia.

  • Additional cases:

    • 5 secondary cases from lab accidents or sexual intercourse.

    • 2 further cases reported in Belgrade, Serbia.

  • Case Severity: 25% of cases resulted in severe haemorrhagic shock.

    • 7 total deaths recorded.

  • Disease linked to imported African Green Monkeys from Uganda.

  • First identification of a virus new to science.

  • No further cases until 1975 (tourist in Rhodesia/Zimbabwe) and 1980 (1 primary and 1 secondary case in Kenya).

Outbreak Data

Historical Context of MVD

  • MVD Understanding

    • Until 1976, MVD lacked comprehensible context.

    • Emergence of Sudan Disease in Zaire (now DRC) and exposure timeline:

      • June 27, 1976: First case found - a factory storekeeper develops fever, headache, and chest pains.

      • June 30, 1976: Patient experiences hemorrhagic shock.

      • July 6, 1976: Patient dies; 48 total cases with 27 deaths linked to the index case.

      • Eventual toll: 117 deaths, 284 cases (CFR of 42%).

      • Notable transmission failures: reused 5 syringes at a local hospital without proper sterilization procedures.

      • August 22, 1976: Second index case in Zaire; traveled after meat purchase.

      • Overall case count rises to 318 with an 88% CFR.

Infection Transmission and Symptoms

Filovirus Characteristics

  • Structure of Filoviruses

    • Components include:

      • Glycoprotein (GP)

      • Nucleocapsid (NP and VP35)

      • Envelope enclosing a negative sense single-stranded RNA genome approximately 19 kb long.

  • Virus Types

    • MVD: Caused by Marburg virus (MARV) and Ravn Virus (RAVV).

    • EVD: Caused by Ebolavirus species (Ebola virus (Zaire), Sudan virus, Tai Forest virus, Bundibugyo virus, Reston virus).

Epidemiology and Reservoirs

  • Reservoir Hosts

    • Bats are believed to be the primary reservoirs for various filoviruses, including Lloviu virus, Mengla virus, and Dehong virus.

  • Transmission Mechanism

    • Filoviruses enter host cells via the Niemann-Pick type C1 (NPC1) protein.

    • Variations in NPC1 sequences across bat species dictate host specificity for filoviruses.

    • Evidence suggests human NPC1 mutations may influence virus entry.

One Health Approach

  • Correlations

    • Connection between deforestation, farming, and incidences of Ebola disease.

    • Global economic factors facilitate rapid movements of contaminated biological agents.

  • Strategic Recommendations

    • Emphasize cross-sectoral collaboration for epidemic responses.

    • Encourage regular inter-sector meetings for proactive teamwork and program ownership.

Ebola Timeline (2013-2016)

  • Significant Epidemics

    • Large-scale cases:

      • More than 100 cases reported in Sudan and DRC (602 cases, 431 deaths).

      • Over 28,600 cases, exceeding 11,300 deaths reported during the West Africa outbreak with estimation of 17-70% unreported.

    • Lesser outbreaks noted in various years (with <100 cases): 1976, 1979, 1983-1984, 1995, etc.

Control Measures for Filovirus Outbreaks

  • Lessons from Ebola Response

    • Quick response is imperative in controlling outbreaks.

    • Essential actions include hunting the virus actively, stopping transmission chains, and engaging communities.

    • Importance of field epidemiology: including diagnostics, contact tracing, and safe management of the sick.

  • Community Importance

    • Trust and communication with communities are key for effective intervention.

    • Risk communication strategies are vital for changing behaviours around safe burial practices and supporting survivors.

Diagnostics and Treatment

  • Diagnosis of EVD/MVD

    • Employing RT-PCR for early-stage diagnosis, which is quick and uses inactivated samples.

  • Supportive Treatment

    • Crucial elements include rest, hydration, pain management, and coagulation control.

  • Antiviral Options

    • Monoclonal antibody therapy: mAb114 or Imazeb for Ebola (Zaire) only.

    • Development in progress for Sudan virus disease.

  • Vaccination

    • Vaccines approved for Ebola (Zaire): Ervebo (a recombinant vaccine) and Zabdeno/Mvabea (adenovirus-based).

Summary of Filoviruses

  • Pathogenic Nature

    • filoviruses classified as highly pathogenic negative sense ssRNA viruses.

  • Disease Association

    • Responsible for MVD and EVD.

  • Reservoir Relationship

    • Linked to bat species, with transmission attributed to exposure to infected animals.

  • Healthcare Infrastructure

    • Limited healthcare support is a significant factor in amplifying outbreaks.