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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