Swine Flu Olga Emgushov, MD, MPH Director Epidemiology/Public Health Preparedness Brevard County Health Department April 30, 2009
Current Swine Influenza Situation Updated frequently on CDC website http://www.cdc.gov/swineflu/ 109 cases in US with 1 death 57 confirmed cases around the globe with 7 deaths (Mexico) Mexico(26), Canada (13), UK (5), Spain (4), Germany/New Zealand (3 each), Isreal (2), Austria (1) WHO phase 5 (evidence of significant human- human transmission) a strong signal that a pandemic is imminent and time to finalize plans US declared public health emergency which sets certain activities in motion such as the Strategic National Stockpile (antiviral drugs) vaccine development
What is Swine Flu? Respiratory disease of pigs caused by a type A influenza virus that causes regular outbreaks in pigs People do not normally get swine flu However this current swine flu is contagious and spreading from person to person we just are not sure how easily it is spreading (can NOT get if from eating pork)
CDC Swine origin Influenza A (S-OIV) Case Definition (4/29/09 2am) Confirmed: Person with an acute febrile respiratory illness with lab confirmed S-OIV infection by CDC Probable: Person with acute febrile respiratory illness who is positive for influenza A, but negative for current seasonal influenza
Suspected S-OIV Person with acute febrile respiratory illness with onset Within 7 days of close contact with a confirmed case Within 7 days of travel to affected community Resides in affected community (>1 confirmed case)
Seasonal Influenza Spreads from person to person through respiratory droplets usually coughing, sneezing within 3 feet but can contaminate surfaces and then spread by touching one s eyes, nose or mouth
Season Influenza in the US 20% of the population become sick 200,000 are hospitalized 36,000 die each year This past season there were 8 pediatric deaths (<18yo)
Communicability How does someone with the flu infect someone else? Infected people can infect others beginning 1 day before symptoms appear and up to 7 days after becoming sick
How do I protect myself and my family? Most important wash your hands often! (studies 4x day, hand sanitizers also) Avoid close contact with sick people Stay home when you are sick Cover mouth and nose when coughing/sneezing Avoid touching your eyes, nose, mouth Stay in good health (sleep, exercise, diet)
What is BCHD doing? Active Surveillance Sentinel Physicians testing first 5 ILI/week plus suspected cases All physicians/labs in county directed to test suspected cases Working with community partners (EOC, school, law, fire, etc) Following pandemic influenza plan In Rapid Response and Containment Phase
Rapid Response and Containment Find all the cases of the infectious disease and isolate them voluntarily at home Monitor the close contacts if they get sick they count as cases their contacts become new monitored contacts
Definitions Isolation Separation of ill persons with contagious diseases For ill people Usually in hospital, but can be at home or in a dedicated isolation facility Quarantine Separation or restriction of movement of select person(s) For people exposed but not ill Home, institutional, or other forms ( work quarantine ) Voluntary vs. compulsory
Social Distancing and Infection Control Social distancing (contact interventions) School closure Work closure (telecommuting) Cancellation of public gatherings Infection control (transmission interventions) Face masks Cough etiquette Hand hygiene
3 probable cases in FL Orange, Broward, Lee Awaiting CDC testing Have been tested by FL DOH state lab and are flu A positive and human H1 and H3 (current seasonal flu) negative Question? Is Orange County part of our community? I am still waiting state DOH guidance
Containment Unlikely Without intervention, expect international spread in 1 month and U.S. cases in 1 to 2 months. Failed containment may still delay international spread by 1 month Severe travel restrictions may delay U.S. cases by 1-4 weeks
Community-Based Interventions 1. Delay disease transmission and outbreak peak 2. Decompress peak burden on healthcare infrastructure 3. Diminish overall cases and health impacts
EPI curve #1 Pandemic outbreak: No intervention #2 Daily Cases #3 Pandemic outbreak: With intervention Days since First Case
1918 Weekly Excess Death Rate by City 0.018 0.016 Excess s Death Rate 0.014 0.012 0.01 0.008 0.006 0.004 Baltimore Boston Milwaukee Minneapolis Philadelphia Pittsburgh St. Louis 0.002 0 9/14/1918 9/21/1918 9/28/1918 10/5/1918 10/12/1918 10/19/1918 10/26/1918 11/2/1918 11/9/1918 11/16/1918 11/23/1918 11/30/1918 12/7/1918 12/14/1918 12/21/1918 12/28/1918 Date
Susceptible to Targeted Attack 1918 Age-Specific Attack Rates
Who Infects Who? To Children To Teenagers To Adults To Seniors Total From From Children 21.4 3.0 17.4 1.6 43.4 From Teenagers 2.4 10.4 8.5 0.7 21.9 From Adults 4.6 3.1 22.4 1.8 31.8 From Seniors 0.2 0.1 0.8 1.7 2.8 Total To 28.6 16.6 49.0 5.7 Children/Teenagers 29% Adults 59% Seniors 12%
1.9 Layered Interventions 2.1 Close schools Keep kids home 1.5 HH quarantine 1.2 Social distancing 1.9 cases HH & community transmission 1.5 HH & community transmission relative importance of HH & workplace transmission 1.2 cases relative importance of workplace & community 0.9 cases
Population-based Containment Influenza Treatment Isolation Prophylaxis Symptomatic / Infectious Susceptible Exposure Quarantine / Isolation Social Distancing Liberal Leave School Closure Infection Control Latent / Infectious Asymptomatic / Infectious Infection Control Social Distancing School Closure Targeted Social Distancing Shunting
Shape of an Epidemic
Susceptible to Targeted Attack
Susceptible to Targeted Attack
40 Value of Combining Strategies Ferguson Model 30 20 10 0 Clinical attack rate Base case (Ro=2.0) 90% case treatment + school closure 90% case treatment + school closure + 90% household prophylaxis Source: Ferguson N, Nature (online) April 26, 2006 90% case treatment + school closure + 90% household prophylaxis + 70% household quarantine
Combining strategies Glass model: Targeted Social Distancing 30 % of po opulation 25 20 15 10 5 0 Clinical attack rate Base case (Ro ~ 1.6) School closure alone School closure + targeted social distancing (10% compliance) School closure + targeted social distancing (30% compliance) School closure + targeted social distancing (50% compliance) School closure + targeted social distancing (90% compliance)
Evidence to Support School Closure Children are thought to be the main introducers of influenza into households. Children appear to be more susceptible to influenza and more infectious than adults in well-designed prospective studies of risk factors of influenza transmission in households. Nationwide school closure in Israel during an influenza epidemic resulted in significant decreases in the diagnoses of respiratory infections (42%), visits to physicians (28%) and emergency departments (28%), and medication purchases (35%).
What do the Modeling Results Mean? Not proof of efficacy or effectiveness, BUT offer reason for optimism regarding non-pharmaceutical interventions Suggest that maximal effectiveness will be achieved by appropriate layering and timing Need to be evaluated based upon assumptions and validated against experience