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Influenza

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Influenza Influenza Presentation Transcript

  • Influenza
    V.Biaukula
  • Pandemic
    Annual Epidemics
    Influenza Virus Subtypes
    Influenza A
    Influenza B
    Influenza C
  • Structure of influenza virus
    NA (neuraminidase)
    Two surface antigens
    HA (hemagglutinin)
  • Why influenza epidemics every year?
    ‘Antigenic drift’
    - Minor changes in surface antigen
    - No protection from previous immunity
  • H1
    N1
    Subtypes of Influenza A Virus
    H2
    N2
    N3
    H3
    H4
    N4
    • Many subtypes (H and N)
    • 3 subtypes have caused human epidemics
    • H1N1
    • H2N2
    • H3N2
    H5
    N5
    H6
    N6
    H7
    N7
    H8
    N8
    H9
    N9
    H10
    H11
    H12
    H13
    H14
    (Karl G Nicholson, et al Lancet 2003; 362: 1733-45)
    H15
  • Avian Influenza (H5N1)
    1st seen in 1997
    History of contact to dead/sick poultry
    Highly pathogenic
    (Case Fatality Rate 60%)
    Most cases seen in children and adults <40yrs, most deaths in 10-19 yr old.
  • Avian Influenza (Bird flu)
  • Influenza Pandemics
  • Influenza Pandemics cause high morbidity & mortality
    Credit: US National Museum of Health and Medicine
    1918
    1957
    1968
    “Hong Kong Flu”
    “Spanish Flu”
    “Asian Flu”
    20 - 40 m deaths
    1 - 4 m deaths
    1 - 4 m deaths
    A(H1N1)
    A(H2N2)
    A(H3N2)
  • INFLUENZA PANDEMIC in the PACIFIC ISLAND HISTORY - 1918
    Some Pacific Islands amongst the worst affected:
    • 1/3 to ½ of the pop. affected & ¼ died in some PICTs
    • Samoa (22% pop. Killed -7542 deaths),
    Fiji (5% ~9000), Tonga (6%), Nauru (6%)
    French Polynesia: Tahiti (25%) Guam (5%)
    Others were totally spared:
    • American Samoa (strict maritime quarantine)
    • Kiribati, Tuvalu, Solomon Islands & Vanuatu (Australian quarantine policy for outgoing steamships exclusively servicing these islands)
  • 1st wave generally mild
    Historically 2nd wave associated with greater morbidity and mortality.
    Pandemics occur when a novel virus infects a community
  • Pandemic H1N1
    As of 12 July lab confirmed cases in 214 WHO member states; 18337 deaths
    World wide pandemic activity is low.
  • Nasophaeyngeal swab to confirm influenza
    Must be collected within 3 days of onset of symptoms
    Must have fever with cough or sore throat.
  • Critical issues for Infection control
    Avoid crowding patients together, promote distance between patients
    Protect mucosa of mouth and nose
    Perform hand hygiene
  • Standard precautions
    Hand hygiene
    Respiratory hygiene/cough etiquette
    Avoid touching your face
  • Environmental cleaning
    Environmental surfaces to be kept clean; wipe with Sodium hypochlorite 1% (Janola). Also hydrogen peroxide, chlorine, detergents, iodine based antiseptics and alcohols.
    Influenza can survive on environmental surfaces:2-8hours
  • Pandemic (H1N1) 2009
    Clinical management
  • Influenza Like Illness (ILI)
    • Sudden onset of fever (38ºC or higher, if no thermometer available, reported chills or high temperature)
    • At leas one of the following symptoms: cough, sore throat, runny nose, nasal congestion; in the absence of alternative diagnosis.
  • Severe Acute Respiratory Illness (SARI)
    Meets ILI case definition AND
    Shortness of breath or difficulty breathing
    AND
    Requiring hospital admission.
  • High risk group for severe disease
    3rd trimester pregnancy, under 2yrs, 65+ yrs, diabetics, long term steroid therapy, chronic lung and heart disease, hematological disorder.
    Neurological disorders can increase risk of severe disease in children.
    Large proportion of severe & fatal cases: obese & morbidly obese, ye obesity hasn’t been recognized as a risk factor.
  • Majority have uncomplicated ILI, recovery within a week, even with no medical Rx.
    Severe cases deteriorate about day 3 to 5
    Rapid deterioration, many progress to respiratory failure within 24 hours – require IMMEDIATE ICU admission.
  • Treatment
    Oseltamivir (Tamiflu):used in cases with high risk of severe disease
    Rx must be started early to reduce disease severity & improve survival chances, even without confirmatory test.
    Paracetamol, Vit. C, Increase fluid intake
  • Vaccination
    Most effective preventive tool
    May prove less effective if virus evolves rapidly, and virus may get around growing immunity in the population.
  • Must remain alert
    Second wave may or may not occur
    Pandemic continues, virus may evolve without it being possible to predict when.
  • References
    http://www.cdc.gov/flu/avian/outbreaks/current.htm
    http://www.who.int/csr/don/2010_07_16/en/index.html