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Simulated epidemics to evaluate H1N1 pandemic preparedness strategies / MIDAS / ASPR-BARDA 9 October 2009. Don Burke, M.D. Dean, Graduate School of Public Health. Don Burke, PI Ron Vorhees , Allegh County Epidemiologist Rick Zimmerman, Community Health Physician
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Simulated epidemics to evaluate H1N1 pandemic preparedness strategies / MIDAS / ASPR-BARDA9 October 2009 Don Burke, M.D. Dean, Graduate School of Public Health
Don Burke, PI Ron Vorhees, Allegh County Epidemiologist Rick Zimmerman, Community Health Physician John Grefenstette, Computer Scientist Cho-Cho Lin, Economist Sandra Quinn, Behavioral Scientist Jim Stark, Epidemiol grad student Shanta Zimmer, InfDis Physician Shawn Brown, Computer Scientist Roni Rosenfeld, Computer Scientist Maggie Potter, Lawyer & Public Health Practice Bruce Lee, Int Med Physician & Operations Rsch
Allegheny County Pennsylvania Model Parameters Washington DC Metro Region • Total Population = 7,414,562 • Workers = 3,714,125 • Firms = 204,691 • Students = 1,369,980 • Schools = 2,443 Total Population = 1,242,755 Workers = 601,022 Firms = 48,595 Students = 212,315 Schools = 484 Total Population = 11,863,395 Workers = 5,391,651 Firms = 312,473 Students = 2,176,168 Schools = 4,319
Location of influenza transmission Communities Workplaces 33% 37% • 16% infections in schools • 21% infections in workplaces Schools (Applies to an epidemic R0 = 1.9) 30% Homes
Attached are two visualizations. They are both performed with the DC Metro model. 1) Oct_AR15 corresponds to seeding the DC area with 100 infections on Sept 17th and starting vaccination on Oct 1st. The model was calibrated to produce a serological attack rate of 15%, and 2/3 of the infections are symptomatic. We are using a 50% Vaccine coverage rate and prioritizing based on the ACIP recommendations (school age kids, heath-care workers, etc.). a. The first plot is an unmitigated epidemic b. The second is with the vaccination implemented c. The third is with 2 week reactive school closures and vaccination d. The fourth is with 2 week system wide school closures and vaccination e. The fifth is with giving 50% of symptomatic AVs that reduce their infectivity by 16%, 2 week system wide school closures and vaccination. f. 2) Oct_AR25 are the same runs, but with the model calibrated to produce a serological attack rate of 25%.
Epidemic scenarios • Moderate transmissibility (R0=1.6) • Peak in October or November • Lower transmissibility (R0=1.3) • Peak in November or December
Epidemic peak and vaccine supply 16 Vaccine production data taken from BARDA (September 24, 2009) and assumes 1 dose per person
Ventilator Capacity and Demand Visualization of the ventilator data runs. Simulation without spatial demographics. The clinical attack rate is 17% in the epidemic. The ventilator data was produced with the assumptions at 2/3 symptomatics, 0.7% symptomatic are hospitalized and that 7.5% of hospitalized patients end up on ventilator. The key to the map is as follows, and is colored based on the capacity that is present in each county: Light Green = 0-10%Green = 11-50%Dark Green = 50-100%Red > 100%Purple no capacity, but have at least one patient.
Remaining Key Problems / Sources of uncertainty • “Now-casting”: How can we estimate the past and current spatio-temporal patterns • of transmission? • What is the ratio of Symptomatic / Total infections ? • “Fore-casting”: Will there be a swine “Third Wave” this winter? • How strong is pandemic vs seasonal “virus interference”? • How strong is seasonality and will there be a future winter peak due to • seasonal forcing ? • Why are older persons being spared? Immunity or connectivity?
“Now-Casting” • The greatest source of uncertainty now in our models is where we are on the epidemic curve: the “Now-casting” problem • In order to appropriately respond to the evolving situation with as much accuracy as possible, understanding the current status of the epidemic is critical.
Potential Data Sources • CDC for State level data and County level data • Individual State websites • Individual State Epidemiologists (Pennsylvania) • PRISM / Insurance companies • Emerging Infection Program sites • BioSense • ? Others
The most accurate and timely data available should be used as a tool to parameterize dynamic models in response to the immediate situation.This is necessary if MIDAS is to be as helpful as it can be.