Community Interventions for Pan Flu— Lessons from History and Modeling Cathy Slemp, MD, MPH WV...
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Transcript of Community Interventions for Pan Flu— Lessons from History and Modeling Cathy Slemp, MD, MPH WV...
Community Interventions for Pan Flu—Lessons from History and Modeling
Cathy Slemp, MD, MPH
WV Bureau for Public Health
November 2006
Influenza Pandemic Viruses
Requirements:– A new influenza A subtype that can infect humans
AND– Causes serious illness
AND– Spreads easily from human-to-human
H5N1 meets the first two prerequisites,
but not the last
Next pandemic virus may or may not be due to a variation of current H5N1 virus
Update:H5N1 in Humans – 2003-2006
• As of October 31, 2006: 256 cases, 152 deaths (~60%)– Ten countries
• Sporadic, with occasional clusters
• Most had close contact with sick poultry
• Few cases of probable, limited human-to-human transmission
• All lived in countries with poultry outbreaks
Flu Pandemics Happen. (10 in last 300 years)
Impacts of Past Pandemics
Pandemic Deaths in the US
Deaths Worldwide
Population Affected
Spanish Flu (H1N1)
1918-1919
500,000 40 million Persons 20-40 years old
Asian Flu (H2N2)
1957-58
70,000 1-2 million Infants, elderly
Hong Kong Flu (H3N2)
1968-69
36,000 700,000 Infants, elderly
IMPACT CAN BE DRAMATICDaily Deaths in Ohio - 1918
Brodrick OL. Influenza and pneumonia deaths in Ohio in October and November, 1918. The Ohio Public Health Journal 1919;10:70-72.
Sample Estimate of Pandemic Morbidity/Mortality, West Virginia*
• Characteristic Moderate (1957-68-like) Severe (1918-like)• Illness 540,000 (30%) 540,000 (30%)• Outpatient 270,000 (50%) 270,000 (50%)• Hospitalization 5,314 60,813• ICU Care 791 9,123• Ventilators 399 4,558• Deaths 1,284 11,690
* Based upon DHHS U.S. estimates applied to WV population numbers. These are in the absence of potential interventions.
What we don’t know … about the next pandemic
• When will it occur?• Which virus will cause it, H5N1 or another?• Who will be most at risk (Elderly and infants? Other?)• How severe an illness will it cause?• Will there be multiple waves?• Will antiviral medication work?• How long until we have a vaccine?• What are the best control measures?
Community-Based Interventions
1. Delay outbreak peak2. Decompress peak burden on hospitals / infrastructure3. Diminish overall cases and health impacts
DailyCases
#1
#2
#3
Days since First Case
Pandemic outbreak:No intervention
Pandemic outbreak:With intervention
Cumulative Excess Mortality by Location in 1918
0100200300400500600700800900
1000
0 10 20 30 40
Location
Exc
ess
Mo
rtal
ity
/
10
0,00
0 P
op
ula
tio
n
McLaughlin AJ. Epidemiology and Etiology of Influenza. Boston Medical and Surgical Journal, July 1920.
Weekly mortality data provided by Marc Lipsitch (personal communication)
1918 Death Rates: Philadelphia v St. Louis
0
2000
4000
6000
8000
10000
12000
14000
16000
9/15
/22
9/22
/22
9/29
/22
10/6
/22
10/1
3/22
10/2
0/22
10/2
7/22
11/3
/22
11/1
0/22
11/1
7/22
11/2
4/22
12/1
/22
12/8
/22
12/1
5/22
12/2
2/22
12/2
9/22
Date
Dea
ths
Rat
es /
100
,000
Po
pu
lati
on
(A
nn
ual
Bas
is)
PhiladelphiaSt. Louis
Washington DC v Seattle
0
20
40
60
80
100
120
140
160
Date
Dea
ths
/ 10
0,00
0 P
op
ula
tio
n
SeattleWashington, DC
Peak Aggregate (1918)Wash DC 147 550Seattle 52 335
Influenza Transmission
Leave original host
Survive in transit
Delivered to a susceptible host
Reach a susceptible part of the host
Escape host defenses
Multiply and cause illness
Viruses:Facemasks, cough etiquetteFacemasks, cough etiquette
CleaningCleaning, , handwashinghandwashing
Social distance, cohorting Social distance, cohorting
Facemasks, handwashing Facemasks, handwashing
Vaccination Vaccination
Potential Tools in Our Toolbox
• Our best countermeasure – vaccine – will probably be unavailable during the first wave of a pandemic
• Antiviral treatment may improve outcomes but will have only modest effects on transmission
• Antiviral prophylaxis may have more substantial effects on reducing transmission
• Infection control and social distancing should reduce transmission, but strategy requires clarification
Suppression
Ro = 0.67,
Progression = 1:2:4:3:2
Exponentiation
Ro = 2.0,
Progression = 1:2:4:8:16
Effect of Increasing Social Distance on Epidemic Dynamics
Increasing “Social Distance”
“Community Shielding” Measures Close or alter high risk transmission environments e.g.
schools, daycare centers if supported by epidemiology Cancel large public gatherings (concerts, theaters) Minimize other exposures (market, church, public transit) Encourage ill and exposed to stay home (I & Q) Worksite adaptations (e.g., telecommuting, etc.) Scaling back transport services (holiday schedule)
Consider additional community measures COOP to minimize economic impact Surgical masks, barrier precautions, hand hygiene
Value of combining strategies – Longini model
0
10
20
30
40
50
60
70
Clinical attack rate Antiviral stockpile needed
Base case (Ro=1.9)Generic social distancingSchool closureSchool closure + generic social distancing60% Case treatment + 60% household prophylaxis60% Case treatment + 60% household prophylaxis + 60% social prophylaxis (60% TAP)60% TAP + School closure + generic social distancing
Conclusions
• Models suggest that partially effective interventions, when used in a layered manner, may be highly effective in controlling the spread of influenza in a community.
• Mitigation strategies appear to be most effective when implemented in a uniform manner early in an outbreak.
• When used as part of a layered strategy, models suggest that social distancing measures can have a significant impact on disease transmission, even if one assumes low rates of compliance and effectiveness.
What are limits of this data?
• Observational data from 1918; data incomplete; cannot link cause and effect
• Modeling impact of interventions useful, but– Doesn’t yet incorporate people’s behavioral
responses to flu itself or to our interventions– Doesn’t incorporate secondary consequences of
interventions (e.g., effects of school closure on education, workforce, etc.)
• Does help shape discussion.
Community Mitigation Strategies Carry Consequences That Should Be Anticipated and
Incorporated into Pandemic Planning
• Economic impact and potential disruption of services due to absenteeism
• Issues associated with sequestration of children• Home-based care• Disproportionate impact on certain populations• Administration of antiviral medications
– As treatment without rapid diagnostics– As prophylaxis to household contacts of ill persons
These and other consequences may occur in the absence of community-wide interventions, as a result of spontaneous action by the public.
Workplace / Classroom Social Density
http://buildingsdatabook.eren.doe.gov/docs/7.4.4.xls
11.7 feet 3.9 feet
7.8 feet
Elementary Schools
Hospitals
Offices
16.2 feet
Residences
Households in the United States
28 million
37 million
28 million12 million
Source: U.S. Census Bureau, Population Division, Current Population Survey, 2003 Annual Social and Economic Supplementhttp://www.census.gov/population/www/socdemo/hh-fam/cps2003.html
66 million
18 million
9 million8 million5 million
Labor Status of Parents
Source: U.S. Census Bureau, Population Division, Current Population Survey, 2003 Annual Social and Economic Supplementhttp://www.census.gov/population/www/socdemo/hh-fam/cps2003.html
Macroeconomic Analysis
• Preliminary macroeconomic analyses of the impact of community-wide interventions have been performed, using several economic models
• These models predict supply-side impacts that range from a decrease in overall economic impact as a result of community-wide interventions, to a modest increase in impact
• These estimates do not incorporate the costs associated with lives lost during a severe pandemic
• If an economic value is assigned to lives lost during a severe pandemic, community-wide interventions result in a 5-10 fold decrease in overall cost
So, Recent Analyses Suggest That Community Actions May Significantly Reduce Illness and
Death Before Vaccine is Available
Early and uniform implementation of such measures as:
• School closure• Keeping kids and teens at home• Social distancing at work and in the community• Encouraging voluntary home isolation by ill individuals and
voluntary home quarantine by their household contacts• Treating the ill and providing targeted antiviral prophylaxis
to household contacts• Implementing measures early and in a coordinated way
A Layered Approach
Individual / Household / Agency
Hand hygieneCough etiquetteInfection controlLiving space controlIsolation of illDesignated care providerFacemasks
Community
Isolation of illTreatment of illQuarantine of exposedProphylaxis of exposedSchool closureProtective sequestration of childrenSocial distancing
- Community- Workplace
Liberal leave policies
International
Containment-at-sourceSupport efforts to reduce
transmissionTravel advisoriesLayered screening of travelersHealth advisoriesLimited points of entry
Epidemiology Drives Approach(Targeted)
Mild Moderate SevereCase Fatality Rate ≤ 0.1% 0.1 - 0.5% ≥ 0.5%
Isolation Yes Yes Yes
Treatment Yes Yes Yes
Quarantine No ??? Yes
Prophylaxis High-risk individuals High-risk individuals Yes
School Closure Reactive Punctuated ??? Proactive
Protective sequestration High-risk individuals High-risk individuals Children
Community social distancing
High-risk individuals Encouraged Encouraged + selective closures
Workplace protections Encourage good hygiene
Social distancing Aggressive social distancing
Liberal leave policies Confirmed influenza Influenza-like illness ILI and/or sick family members
SAMPLE
Things to consider in choosing strategies
• Disease severity• Information on the disease (e.g., are there high risk
subgroups? How effective are antivirals? etc.)• Ability to practically implement the control measure• Public acceptability of the control measure• Secondary impacts of the measure—are we doing
more harm than good? • What should be implemented by communities and
what centrally? Is a common approach important?• Ethical considerations
What Can Communities Do Now?
• Education of leadership about the need for cross-sectoral planning
• Engagement of non-health communities: education, private sector, labor, faith communities, NGO’s, the public
• Development of Community-wide plans
• Scenario-based discussions of implementation
• Plan how to support and protect staff
Leadership
Imagination
Resiliency of Individuals, Agencies, and Communities
What does this take? (Now and when the time comes)
Contributors to Historical Analysis and Modeling
HSC/NSPI Writing Team
Richard Hatchett, MD
Carter Mecher, MD
Laura McClure, MS
CDR Michael Vineyard
NIH
James Anderson, PhD
Irene Eckstrand, PhD
Peter Highnam, PhD
Ellis McKenzie, PhDCDC
David Bell, MD
Martin Cetron, MD
Rachel Eidex, MD
Lisa Koonin, MN, MPH
Anthony Marfin, MD
Modelers
Joshua Epstein, PhD
Stephen Eubank, PhD
Neil Ferguson, PhD
Robert Glass, PhD
Betz Halloran, PhD
Nathaniel Hupert, MD
Marc Lipsitch, MD
Ira Longini, PhD
HSC
Rajeev Venkayya, MD
Ken Staley, MD, MPA
RTI
Philip Cooley, PhD
Diane Wagener, PhDUniversity of Michigan
Howard Markel, MD
Department of Education
Camille Welborn, MS
Department of Labor
Suey Howe, JD
Department of Finance - Canada
Steven James
Timothy Sargent
Department of the Treasury
Nada Eissa, PhD
Chris Soares, PhDJohn Worth, PhD
NVPO
Bruce Gellin, MD
Ben Schwartz, MD
NSC
Rita DiCasagrande, MS
CEA
Steven Braun, PhD
Get Informed, Be Prepared!
RESOURCES
WVBPH: Div Threat Prep or DSDC Your Emergency Management Agency and
Local Health Department http://www.wvflu.org http://www.pandemicflu.gov ASTHO (www.astho.org) and NACCHO (
www.naccho.org) Websites CDC website (www.cdc.gov)