Influenza biology and epidemiology

The course of illness  Symptoms  Fever, headache, body aches, fatigue  Cough, sore throat, runny nose  Duration: 2-7 days  Incubation period: 1-5 days  Susceptibility depends on prior exposure  Complications: bacterial infection

Susceptible Exposure Infection Symptoms Resolution Infectious disease progression

Susceptible Exposure Infection Symptoms Resolution Infectious disease progression Period of infectivity (SARS)

Susceptible Exposure Infection Symptoms Resolution Infectious disease progression Period of infectivity (flu)

The influenza virus H1N1

Virus mutation  Drift  Relatively minor changes in the antigens  Partial immunity to subsequent infection  Shift  Radical change in the antigens  No immunity conferred from earlier infections

Shift: Pandemic

Jumping between people and animals

Avian fluSeasonal and Pandemic flu Jumping between people and animals

Avian flu

Epidemic transmission

Animal culling

Treatment  Tamiflu  Relenza  After symptoms  Post exposure prophylaxis

Social distancing  Isolation  Quarantine  Face masks  Cancel social gatherings

Vaccine  This year’s seasonal vaccine based on last year’s strains  No vaccine yet for H5N1  Can’t anticipate final mutation to a pandemic strain  Development 6-8 months after pandemic strain identified

Preparation and response levels Country States & Provinces Cities and Counties Businesses and Civil Society Individuals and Families WHO

1918: Pandemic waves

1918: Illness rates by age

1918: Mortality rates by age

1976: Premature action