Hemorrhagic

Viral Pathogens

  • Key focus on Hemorrhagic Viruses:

    • Arboviruses: Dengue virus and Yellow fever virus

    • Ebolavirus

    • Hantavirus (Seoul virus)

    • Lassa virus

    • Marburg virus

Dengue and Yellow-fever Viruses

  • Classification:

    • Both are enveloped RNA viruses.

    • Dengue virus has four serotypes (1-4).

  • Transmission:

    • Primarily through Aedes mosquitoes (same as Zika and Chikungunya).

    • Congenital transmission (Dengue only).

    • Rare transmission via blood transfusion and organ transplants (Dengue only).

    • Reservoirs:

      • Humans for Dengue virus.

      • Monkeys for Yellow fever virus.

    • Transmission cycles in Yellow fever:

      • Intermediate (savannah) cycle in Africa; mosquitoes infecting humans near jungle border areas.

      • Transmission possible from monkeys to humans and from human to human.

Geographic Distribution and Risk Factors

  • Geography/Seasonality:

    • Endemic regions defined by mosquito habitat.

    • Increased prevalence during the summer months.

  • Risk Groups:

    • Individuals entering endemic areas.

    • People with outdoor exposure.

    • Blood transfusions (Dengue screening absent).

Vaccination Recommendations

Clinical Syndromes of Yellow Fever and Dengue

  • Yellow Fever Virus:

    • Incubation: 3 to 6 days.

    • Initial Symptoms: Flu-like, back pain, nausea.

    • Severe Symptoms (1 in 7): High fever, jaundice, bleeding, shock, and organ failure.

    • Mortality Rate: 30-60%.

  • Dengue Virus:

    • Incubation: 5 to 7 days.

    • 25% of infections are asymptomatic.

    • Mild symptoms may include flu-like symptoms, joint pain, rash.

    • Severe symptoms (1 in 20 symptomatic cases): Shock, internal bleeding, and potential death. Risk increases with previous dengue exposure.

Diagnosis and Treatment of Dengue and Yellow Fever

  • Diagnosis:

    • Antibody detection (note cross-reactivity issues with other arboviruses).

    • Molecular detection.

  • Treatment/Prevention:

    • No specific antivirals; supportive care only.

    • Control of mosquito vector.

    • Vaccines available for Yellow fever and Dengue (limited to specific age and previous infection).

Ebolavirus

  • Classification:

    • Enveloped RNA viruses including Zaire ebolavirus and Sudan ebolavirus.

  • Transmission:

    • Typically involves a "spillover event" from fruit bats or non-human primates.

    • Human-to-human transmission through direct contact with bodily fluids.

    • Can infect through broken skin or mucous membranes.

Ebolavirus Ecology and Risk Groups

  • Geography: Primarily in Africa; no seasonal incidence.

  • At-risk populations:

    • Travelers to areas with hemorrhagic fever outbreaks.

    • Hospital staff caring for patients with hemorrhagic fever.

    • Rural residents in Africa.

Clinical Syndrome of Ebolavirus

  • Incubation Period: 2 to 21 days.

  • Symptoms: Ranges from mild flu-like symptoms to severe hemorrhagic fever (internal and external bleeding).

  • Mortality Rate: Approximately 50%.

  • Diagnosis: Based on clinical history, molecular detection, and biosafety considerations.

Biosafety Levels in Laboratory Settings

  • Levels: Ranking from 1 to 4, determined by risks of infectivity, disease severity, transmission potential, and nature of work.

  • Containment Controls:

    • Safety practices, equipment, and facility construction need to meet specific standards per risk tier.

    • Use of biological safety cabinets (BSC) is essential for higher biosafety levels.

Treatment and Prevention of Ebolavirus

  • Methods:

    • Monoclonal antibodies, supportive care, pain management, fluid replacement.

    • Education on hygiene and contact avoidance.

    • Vaccination available for Zaire ebolavirus. Antibody presence can last for up to 10 years post-recovery.

Lassa Virus

  • Enveloped RNA virus, primarily zoonotic, transmitted from rodents.

  • Transmission: Inhalation, ingestion, or contact with urine/fecal droppings, and human-to-human contact possible through bodily fluid exposure.

  • Geography: Found in tropical Africa and South America, with no seasonal incidence.

Clinical Syndrome and Diagnosis for Lassa Virus

  • Incubation: 1 to 3 weeks; about 80% of infections mild (flu-like symptoms).

  • Severe symptoms: Hemorrhaging, respiratory distress, and potential death within 2 weeks due to multi-organ failure (mortality rate: 15-20%).

  • Diagnosis: Antibody and molecular detection, classified as a BSL-4 pathogen.

  • Treatment/Prevention:

    • Early antiviral administration can be beneficial; supportive and respiratory care required.

    • Emphasis on avoiding contact with rodents and stringent handwashing practices.

Marburg Virus

  • Classification: Enveloped RNA virus.

  • Transmission: Spillover from bats or human-to-human through direct contact with infected fluids.

  • Geography: Primarily Africa, potential seasonal incidence noted.

  • Risk Groups:

    • Individuals entering caves with bats and healthcare workers treating infected patients.

Clinical Syndrome and Diagnosis for Marburg Virus

  • Incubation: 2 to 21 days; progression from mild (flu-like) to severe hemorrhagic symptoms.

  • Mortality Rate: Approximately 50%.

  • Diagnosis: Based on clinical presentation and history alongside molecular detection; also classified as BSL-4 pathogen.

  • Treatment/Prevention:

    • Supportive care, fluid replacement, hygiene education, and avoidance of contact with infected individuals.