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

Update

As of 10/31/06: 256 cases; 152 deaths; most poultry related

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?

Planning Pandemic 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

What can we learn from historical analysis?

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

Thinking ThroughControl Measures

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

Ro = 2R0 = 1

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

What Does Disease Modeling Suggest?

Examining the Potentialof Combined Interventions

%Population Infected

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

Spacing of people: If homes were like schools

*Based on avg. 2,600 sq. ft. per single family home

Spacing of people: If homes were like schools

*Based on avg. 2,600 sq. ft. per single family home

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

A Targeted and Layered Approach

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)