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H1N1 Influenza A pandemic strain

H1N1 Influenza A pandemic strain. Martha Fulford, MD, FRCPC Division of Infectious Diseases McMaster University Medical Centre. Overview of influenza Definition of pandemic pH1N1 Current Status. Influenza. an orthomyxovirus RNA virus.

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H1N1 Influenza A pandemic strain

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  1. H1N1 Influenza Apandemic strain Martha Fulford, MD, FRCPC Division of Infectious Diseases McMaster University Medical Centre

  2. Overview of influenza • Definition of pandemic • pH1N1 • Current Status

  3. Influenza • an orthomyxovirus RNA virus. • contains 8 segments of RNA put together with a protein. • three types: A, B, C. • Influenza A, thought to be of avian origin, is responsible for known human pandemics. • two main surface glycoproteins that allow the virus to attach to and infect a host: • hemagglutinin (HA) • neuraminidase (NA)

  4. Influenza • mutations within the HA and/or NA are called “antigenic drift”. • a continual, ongoing process. • exchange of gene segments between human and animal (avian or swine) viruses results in “antigenic shift”. • result is a new virus to which humans (or animals) have not previously been exposed.

  5. EID. Volume 12, Number 1, January 2006

  6. Influenza • influenza viruses cause annual seasonal outbreaks (‘flu season). • attack rates range between 5 - 20%. • case fatality rate < 0.1%. • 3,000 - 8,000 deaths annually in Canada. • Average of 4,000 deaths from seasonal influenza. (Health Canada, http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/diseases-maladies/pandem-eng.php)

  7. Pediatric Influenza Deaths www.cdc.gov/FLU/ weekly/index.htm

  8. Influenza Pandemic • The term "pandemic influenza” is used when there is global spread of an influenza virus with a new HAsubtype. • WHO requires sustained human to human transmission of a novel virus in at least two WHO geographic regions.

  9. Previous Influenza Pandemics • Influenza pandemics: • 1761-62 • 1833-37 (2% case fatality rate?) • 1889-90 • 1918-19 H1N1 – the Spanish ‘flu • 1957-58 H2N2 – the Asian ‘flu • 1968-69 H3N2 – the Hong Kong ‘flu • 2009 - H1N1 – the pH1N1 (swine flu)

  10. pandemic H1N1 Influenza A • Late March, 2009 an outbreak of a respiratory illness which predominantly affected young people was described in Mexico. • Very quickly, a novel strain of H1N1 Influenza A (swine flu) was identified. • Subsequent rapid worldwide spread. • June 11, 2009 WHO raised its pandemic alert level to 6, the highest level.

  11. pH1N1 Current Status • As of October 4, 2009 WHO reports: • 191 countries reporting cases (out of 195 countries in total) • 375,000 laboratory confirmed cases • 4,500 deaths. • 78 deaths in Canada as of Oct. 13 (including 4 pediatric deaths).

  12. pH1N1 Current Status • As of Oct 13, 1,504 cases hospitalized. • 295 admitted to ICU. • Of the 78 pH1N1 deaths in Canada: • 60.5% female • median age 50 • aboriginal 11.8% • underlying medical conditions 81.7% • pregnant 5.1% http://www.phac-aspc.gc.ca/fluwatch/09-10/w37_09/index-eng.php

  13. pH1N1 Current Status • increasing ILI across the country. • outbreaks declared in > 40 schools, including 6 schools and one day care in Hamilton. • approx. 97% of positive influenza A specimens were pH1N1. • Local % positivity for Influenza A Oct 4-10: • Children < 4:  Influenza A 4%, Parainfluenza 11% • Persons > 4 yrs of age:  Influenza A 11% • People with mild symptoms do not get tested.

  14. pH1N1 Influenza A • incubation period - 1 - 3 days. • shedding of virus likely from one day before onset of symptoms to approx. seven days after onset of symptoms. • young children and the immuno-compromised may shed for longer periods. • majority of infections have resulted in very mild disease.

  15. pH1N1 Clinical Presentation • fever • cough • sore throat • malaise and headache • vomiting & diarrhea (not typical of seasonal) • chills • myalgias & arthralgias.

  16. pH1N1 Clinical Presentation • children may not have typical respiratory tract symptoms but will have: • fever • irritability • lethargy. • with severe infection: • apnea or tachypnea • cyanosis • dehydration • altered mental status.

  17. pH1N1 Risk Factors • People at risk of developing complications: • Children < 2 years • Children aged 6 months – 18 years on long-term aspirin therapy (Reye syndrome) • Pregnant women (particularly 2nd and 3rd trimesters and up to 4 weeks post delivery) • People living in isolated / remote communities • Persons > 65 years • Residents of long-term care facilities

  18. Patients with: • chronic respiratory disease • cardiac disease • morbid obesity (BMI  40, possibly people with BMI  30). • chronic diseases (e.g. diabetes, chronic renal failure, chronic liver disease, chronic metabolic diseases, hemoglobinopathies) • chronic neurologic disorders (which may result in difficulty managing respiratory secretions) • Immunosuppressed (e.g. chemotherapy, HIV, chronic corticosteroids)

  19. H1N1 Severe Disease • Similar to seasonal influenza: • lower respiratory disease (viral pneumonia) • secondary bacterial pneumonia / sepsis • myocarditis / pericarditis • CNS (encephalitis, cerebellitis, febrile seizures, post infectious encephalomyelitis) • toxic shock syndrome • ARDS.

  20. H1N1 and the elderly • Persons born before 1957 seem to be less likely to get ill with the H1N1. • Thought to be due to immunity acquired from exposure prior to 1957. • However, if an older person does get this influenza then she is at risk for developing complications.

  21. H1N1 Treatment • Persons with no risk factors for severe disease no antiviral medication needed; symptomatic treatment only. • Persons at risk for developing severe disease  treat with antiviral medication. • start within 48 hours of onset of symptoms. • Hospitalized patients  treat.

  22. H1N1 Treatment

  23. H1N1 Prevention • Wash your hands. • Cover your nose and mouth when you cough or sneeze. • Wash your hands. • Avoid touching eyes, nose, mouth. • Avoid contact with sick people. • Wash your hands. • Stay home if you are sick. • Social distancing.

  24. H1N1 Prevention • Pre-exposure prophylaxis not currently recommended. • Post-exposure prophylaxis in general is not recommended. • It may be considered for high risk individuals in exceptional circumstances following a documented exposure. • The current recommended strategy is close monitoring for symptoms and early treatment.

  25. H1N1 Vaccine • Vaccination is considered to be one the main tools for prevention of widespread influenza. • In Canada, there will be two vaccines: • adjuvant-inactivated monovalent vaccine • non-adjuvant inactivated monovalent vaccine for pregnant women and children under the age of 3. • Children under age 10 will need a booster.

  26. H1N1 Vaccine • The vaccine is being recommended for: • persons with chronic conditions < 65 • pregnant women • children 6 months to less than 5 years of age • persons residing in remote and isolated settings and communities • Health care workers (all health care system workers involved with the pandemic response or delivery of essential health services) • household contacts and care providers of: • children < 6 months • immunocompromised individuals. http://www.phac-aspc.gc.ca/alert-alerte/h1n1/vacc/vacc-eng.php

  27. H1N1 Vaccine • Others who might benefit include: • children 5 to 18 (inclusive) years of age • first responders (police, firefighters) • Poultry and swine workers • Adults 19 to 64 (inclusive) years of age • Adults 65 years of age and over. http://www.phac-aspc.gc.ca/alert-alerte/h1n1/vacc/vacc-eng.php

  28. Ontario Vaccine Plan • October. Seasonal flu vaccine for: • People over the age of 65 and residents of long-term care homes living in Ontario. • November. H1N1 Vaccine for: • Identified priority groups. • Anyone else who want it. • Next - maybe in January?: • the seasonal flu vaccine will be available to everyone who is six months of age and over who lives, works or attends school in Ontario.

  29. Questions?

  30. Adjuvants • A substance that is added to a vaccine to improve the immune response. • This may be done for various reasons: • dose sparing so that more vaccine doses can be manufactured • to boost the immune response in some patients, e.g. the elderly.

  31. Adjuvants • GlaxoSmithKline is manufacturing Canada’s vaccine. • The adjuvant being used is ASO3 - alpha-tocopherol-based adjuvant system number 3; a squalene based oil-in-water emulsion. • The vaccine is to be supplied in a two-vial format - one containing the antigen and the other the adjuvant.

  32. Genetic factors in distinguishing between "human flu viruses" and “avian influenza viruses" include: • PB2: (RNA polymerase): Amino acid (or residue position 627 in the PB2 protein encoded by the PB2 RNA gene. Until H5N1, all known avian influenza viruses had a Glu at position 627, while all human influenza viruses had a lysine. • HA: (hemagglutinin) Avian influenza HA bind alpha 2-3 sialic acid receptors while human influenza HA bind alpha 2-6 sialic acid receptors. • Swine influenza viruses have the ability to bind both types of sialic acid receptors.

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