What is Influenza? Patricia Daly MD, FRCPC Medical Health Officer and Medical Director of Communicable Disease Control

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1 Vancouver Coastal Health & The Vancouver Coastal Health Research Institute presents: On Call with VGH Experts Lecture Series The Flu and You What is Influenza? Patricia Daly MD, FRCPC Medical Health Officer and Medical Director of Communicable Disease Control Wednesday, November 15, 2006

2 Influenza viruses Types A, B and C all infect humans Type A can infect: Birds Pigs Horses Seals and whales

3 Influenza Type A In humans: Yearly epidemics Occasional pandemics

4 Type A Influenza Viruses Subtyped by surface proteins Haemagglutinin (H) Neuraminidase (N) 16 H types, 9 N types All can infect birds (avian influenza) 3 H types and 2 N types circulate among humans H1,H2,H3 N1,N2 } H3N2, H1N1

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6 How is Influenza Transmitted? Droplets produced when coughing or sneezing Travel 1 metre Settle on surfaces

7 Influenza Epidemiology Incubation period = Time from infection until onset of symptoms Period of communicability = Time a case is infectious to others Infection Symptoms Time Incubation period Period of communicability Days

8 Influenza Morbidity and Mortality Each year: 5 million Canadians (1 in 6) are infected 50,000 will be hospitalized 4,500 will die 1.5 million work-days will be lost In BC about 1,400 people die from the flu and pneumonia Pneumococcal vaccination can prevent secondary pneumonia

9 Influenza Control Vaccination To protect those at high risk of severe illness and death Outbreak Response Antiviral drugs

10 Influenza Vaccine Protects against 3 influenza strains: Type A strains of H3N2, H1N1; B strain At least one strain changes each year New vaccine each fall Virus grown in chick embryo cells 4-6 months to produce Killed virus vaccine cannot cause influenza

11 Composition of Influenza Vaccine Based on recommendations from the World Health Organization Worldwide laboratory surveillance for new strains 2006/07 vaccine: A/New Caledonia/20/99 H1N1 A/Wisconsin/67/2005 H3N2 B/Malaysia/2506/2004

12 Influenza Vaccination in BC >1.1 million doses distributed Recommended and provided free for: Residents of nursing homes, chronic care facilities 65 years of age Children 6-23 months of age 2-64 years with chronic health conditions Household contacts: High risk, 0-23 months of age Healthcare workers First responders Live poultry workers

13 Children under 2 years of age High incidence of hospitalization: 90-1,000 admissions per 100,000 healthy children 12 Canadian Paediatric Hospitals 381 hospitalizations 2004/ hospitalizations 2005/06 (40% under age 2 yrs) 3 influenza associated deaths reported

14 Protecting Children < 2 years old Vaccinate those 6-23 months of age Vaccine may be ineffective under age 6 months 2 doses required, one month apart, the first year vaccinated for those up to 8 years old Vaccinate all household contacts, caregivers of children under 2 years of age Vaccinate pregnant women in their 3 rd trimester

15 Adults and Children 2-64 years with Chronic Health Conditions 1. Cardiac or pulmonary disorder (e.g. asthma) 2. Diabetes and other metabolic conditions 3. Cancer, immunodeficiency (e.g. HIV) or immunosuppression 4. Renal disease 5. Anemia or hemoglobinopathy 6. Conditions with increased risk of aspiration 7. Long-term acetylsalicyclic acid treatment

16 Influenza Vaccine Facts and Myths 1. Influenza vaccine causes the flu. No live virus in flu vaccines Cannot cause the flu

17 Influenza Vaccine Facts and Myths 2. I don t need a flu shot I never get the flu. No one has natural immunity to influenza Each year 1 in 6 Canadians get the flu Healthy adults may experience no symptoms but can still transmit the virus to others

18 Influenza Vaccine Facts and Myths 3. I got the flu shot last year and still got the flu. Vaccine 70-90% effective in healthy adults 30-40% effective in preventing infection in the frail elderly, but they are less likely to die if infected ONLY protects against influenza other respiratory viruses circulate in the fall and winter

19 Influenza Vaccine Facts and Myths 4. Influenza vaccine can cause serious side effects Most people have no side effects after a flu shot, other than a sore arm lasting 1-2 days Allergic reactions rare: Due to severe allergy to vaccine component or egg protein Thimerosal: Preservative NOT associated with any adverse health effects Guillain-Barré syndrome: Extremely rare

20 Thimerosal Thimerosal: Preservative used in multi-dose vaccine vials since the 1930s Prevention of bacterial or fungal contamination 49% mercury (Hg) by weight Metabolized to ethylmercury and thiosalicylate

21 Mercury Concerns Methylmercury ingested in fish, grain in large doses can affect neurologic and renal systems Prenatal exposure to methylmercury from fish may affect later child development

22 Thimerosal in Vaccines No evidence of harm from many studies Exposure limits set for methylmercury, thimerosal contains ethylmercury more easily excreted Periodic injections not the same as daily intake Studies demonstrating harm from mercury had exposure many times greater than from vaccination Influenza vaccines in B.C.: Fluviral TM : 0.01% thimerosal Vaxigrip TM : Trace thimerosal

23 Guillain-Barré Syndrome Acute disorder of the peripheral nervous system causing weakness Annual incidence 1-2 cases per 100,000 More common in adults than children Associated with recent infections diarrhea or respiratory tract

24 Guillain-Barré Syndrome and Influenza Vaccine Increase risk of GBS after swine flu vaccination in the U.S. in 1976 Since 1976: Some studies show no risk, some slight risk (1 case per 1 million vaccinated) Canadian study published this week: Ontario study (universal flu vaccination) 12 years of data One analysis showed slightly increased risk, another did not

25 Influenza Pandemics Pandemic = A global outbreak of influenza New influenza A virus subtype appears or emerges Causes serious illness Spreads easily from person-to-person Seasonal influenza outbreaks: Subtypes of influenza A viruses that are already in existence among people new strains

26 Influenza Virus Changes Influenza virus frequently changes Changes to surface proteins: Hemagglutinin and Neuraminidase Antigenic drift Small changes that occur continuously as virus replicates, producing new strains Antigenic shift Dramatic change in virus proteins producing new subtype (HxNx)

27 Antigenic Shifts and Pandemics New subtypes: Everyone is susceptible Infection with same subtype in the past provides some protection Pandemic possible IF the new subtype: Causes serious human illness AND Spreads easily from person-to-person

28 Pandemic Deaths U.S.

29 Need More Information? List of public health clinics where you can get vaccinated