micro-exam 2 pt2

JSU Influenza

Overview of Influenza

  • Background information is extensive

  • General section will cover specific topics

    • Outer membrane markers

    • Antigenic shift and drift

    • Virus types

    • Specific influenza strains

Outer Membrane Markers

Structure

  • Influenza virus is surrounded by glycoprotein spikes, primarily hemagglutinin (HA) and neuraminidase (NA)

  • These spikes are crucial for virus interaction with host cells

Function

  • Hemagglutinin (HA)

    • Binds to pulmonary cells, facilitating endocytosis of the virus

  • Neuraminidase (NA)

    • Cleaves mucus in the lungs, allowing the virus access to cell surfaces

    • Mucus is a component of the innate immune system

Naming Convention

  • Viruses are classified based on the types of HA and NA present

  • Example: H1N1 refers to specific types of hemagglutinin (H1) and neuraminidase (N1)

Antigenic Drift and Shift

Antigenic Drift

  • Definition: Accumulation of mutations in HA and NA genes within a singular virus strain over time

  • Process:

    1. Virus enters host

    2. Mutations occur during replication

    3. Resulting virus presents a slightly different structure to immune systems

  • This leads to seasonal influenza outbreaks approximately every 2-3 years due to immune evasion

Antigenic Shift

  • Major change caused by reassortment of genes from different influenza viruses in the same host cell

  • Example: Swine and human viruses swapping genes can create a novel virus

  • Typically occurs every 10 years

  • Source locations: Asia due to high hosts (ducks, pigs), facilitating viral reassortment

Virus Types

Classification

  • Four types of influenza viruses: A, B, C, and D

  • Type A: Causes significant epidemics, can undergo both drift and shift

  • Type B: Only undergoes drift, leads to less variation

  • Type C: Generally mild and not harmful, does not cause widespread epidemics

  • Type D: Does not infect humans

Specific Influenza Strains

Spanish Flu (H1N1)

  • Pandemic in 1918 killing an estimated 50-80 million globally, higher mortality rates than typical flu outbreaks

Avian Influenza

  • Comprises various types such as H5N1, H7N9

  • Can have high mortality rates, particularly H5 subtype

Transmission and Symptoms

Location / Transmission

  • Transmitted through respiratory droplets during coughing and sneezing

  • Survives on surfaces for up to 8 hours; touching contaminated surfaces followed by face contact can lead to infection

  • Can spread before and after the onset of symptoms

Signs and Symptoms

  • Common symptoms include:

    • Fever

    • Cough

    • Muscle pain

    • Sore throat

    • Fatigue

Mode of Action

Infection Process

  • Influenza viruses invade epithelial cells via endocytosis facilitated by hemagglutinin

  • New virions bud off host cells, neuraminidase prevents clumping of viruses

Epidemiology

U.S. Statistics

  • Yearly variations in cases, with averages around 50 million infections

  • Approximately 30,000 deaths annually attributed to influenza complications

Treatment and Prevention

Treatment Methods

  • Supportive care is standard; sometimes antibiotics are used for secondary bacterial infections

Preventative Measures

  • Hand hygiene, vaccines tailored yearly based on predicted circulating strains, isolating infected individuals

Conclusion

  • Comprehensive understanding of influenza, including its structure, transmission, and epidemiology, is crucial for effective management and prevention.

  • Continued education on vaccination and outbreak response is necessary for public health.