E & S Loss Control Executive Forum

An Introduction toSeasonal, Avian andPandemic Influenza

Toby L Merlin, MD

Director, Division of Partnerships and Strategic Alliances

November 15, 2006

E & S Loss Control Executive Forum

An Introduction toSeasonal, Avian andPandemic Influenza

Toby L Merlin, MD

Director, Division of Partnerships and Strategic Alliances

November 15, 2006

•Seasonal, avian, and pandemic

•Control measures for individuals, households, and workplaces

•Control measures for communities

•Seasonal, avian, and pandemic

•Control measures for individuals, households, and workplaces

•Control measures for communities

Introduction to InfluenzaIntroduction to Influenza

Definition of InfluenzaDefinition of Influenza

• A contagious disease caused by an RNA virus

- Primarily affects the respiratory tract

- Can cause severe illness and lead to life-threatening complications

• A global infectious disease threat

• An annual public health problem

• A contagious disease caused by an RNA virus

- Primarily affects the respiratory tract

- Can cause severe illness and lead to life-threatening complications

• A global infectious disease threat

• An annual public health problem

Influenza A VirusesInfluenza A Viruses

NANA

HAHA

Subtyped based on surface glycoproteins• 16 hemagglutinins (HA) and 9 neuraminidases

(NA)• Current human subtypes: H1N1, H3N2

Segmented genome

Subtyped based on surface glycoproteins• 16 hemagglutinins (HA) and 9 neuraminidases

(NA)• Current human subtypes: H1N1, H3N2

Segmented genome

Influenza Viruses

•Naturally infect several animal species• Birds

• Mammals including people

•People usually infected only by human viruses

•Wild birds main reservoir for influenza A viruses• All known “A” subtypes circulate in wild birds

• Infect wild and domesticated birds

• Ultimate source for viruses (and virus genes) infecting other animal species

•Naturally infect several animal species• Birds

• Mammals including people

•People usually infected only by human viruses

•Wild birds main reservoir for influenza A viruses• All known “A” subtypes circulate in wild birds

• Infect wild and domesticated birds

• Ultimate source for viruses (and virus genes) infecting other animal species

Avian Influenza A VirusesAvian Influenza A Viruses

H1 – H16H1 – H3

Human Influenza A Viruses

Human Influenza A Viruses

Emergence of Influenza A Viruses in HumansEmergence of Influenza A Viruses in Humans

H1H1

H1H1H3H3

H2H2

H7*H7*

H5*H5*

H9*H9*

19181918

Flu H1N1Flu H1N1

19571957

Flu H2N2Flu H2N2

1968 1968

Flu H3N2Flu H3N2

1980 1996 20021980 1996 2002

1997 2003-2006 1997 2003-2006

1915 1925 1935 1945 1955 1965 1975 1985 1995 2005 20061915 1925 1935 1945 1955 1965 1975 1985 1995 2005 2006

* Avian Flu* Avian Flu

2003 2004

2003 2004

1998 1999

2003

1998 1999

2003

19771977

Antigenic Change:A Key Feature of Influenza

Viruses

Antigenic Change:A Key Feature of Influenza

Viruses

•Change more than other respiratory viruses

•Minor changes occur constantly (“drift”)•Cumulative

•Reason why vaccine is updated each year

•Radical change occurs infrequently (“shift”)•New surface protein (no immunity among

people)

•Change more than other respiratory viruses

•Minor changes occur constantly (“drift”)•Cumulative

•Reason why vaccine is updated each year

•Radical change occurs infrequently (“shift”)•New surface protein (no immunity among

people)

The “Flu” The “Flu”

• Influenza is a viral illness that is easily confused with other infections, such as• Colds• Other viral infections

• Influenza usually is self-limited to about a week of illness

• Complications from influenza can contribute to serious secondary infections

• Influenza is a viral illness that is easily confused with other infections, such as• Colds• Other viral infections

• Influenza usually is self-limited to about a week of illness

• Complications from influenza can contribute to serious secondary infections

Usual Influenza SymptomsUsual Influenza Symptoms

- Fever - Headache- Fatigue - Dry cough- Body aches - Runny or stuffy nose

• Children also may have gastrointestinal symptoms – nausea, vomiting, or diarrhea

- Fever - Headache- Fatigue - Dry cough- Body aches - Runny or stuffy nose

• Children also may have gastrointestinal symptoms – nausea, vomiting, or diarrhea

How Influenza Viruses SpreadHow Influenza Viruses Spread

• Primarily through respiratory droplets

• Coughing

• Sneezing

• Touching respiratory droplets on self, another person, or an object, then touching mucus membranes (e.g., mouth, nose, eyes) without washing hands

• Primarily through respiratory droplets

• Coughing

• Sneezing

• Touching respiratory droplets on self, another person, or an object, then touching mucus membranes (e.g., mouth, nose, eyes) without washing hands

Average Seasonal Impact of Influenza in the United StatesAverage Seasonal Impact of

Influenza in the United States

• >200,000 hospitalizations / year

• about 36,000 deaths / year(>90% in elderly during regular seasons)

• Substantial economic impact • Lost work / school days• Estimated $37.5 billion cost

• >200,000 hospitalizations / year

• about 36,000 deaths / year(>90% in elderly during regular seasons)

• Substantial economic impact • Lost work / school days• Estimated $37.5 billion cost

Pandemic vs. Seasonal InfluenzaPandemic vs. Seasonal Influenza

Seasonal outbreaksCaused by subtypes of influenza viruses that already circulate among people

Pandemic outbreaksCaused by:

• New subtypes• Subtypes that have never circulated among people, or• Subtypes that have not circulated among people for a long time

Seasonal outbreaksCaused by subtypes of influenza viruses that already circulate among people

Pandemic outbreaksCaused by:

• New subtypes• Subtypes that have never circulated among people, or• Subtypes that have not circulated among people for a long time

Three Criteria for a PandemicThree Criteria for a Pandemic

An influenza pandemic is a global outbreak of disease that occurs when

• A new influenza A virus appears or “emerges” in the human population, and

• It causes serious illness in humans, and

• It spreads easily from person to person worldwide

An influenza pandemic is a global outbreak of disease that occurs when

• A new influenza A virus appears or “emerges” in the human population, and

• It causes serious illness in humans, and

• It spreads easily from person to person worldwide

Concerns about Pandemic Influenza

Concerns about Pandemic Influenza

• Rapid global spread (morbidity and mortality)

• Shortages and delays – vaccines and antiviral medications

• Increases burden on hospitals and outpatient care systems

• Simultaneous impacts that disrupt national and community infrastructures

• Rapid global spread (morbidity and mortality)

• Shortages and delays – vaccines and antiviral medications

• Increases burden on hospitals and outpatient care systems

• Simultaneous impacts that disrupt national and community infrastructures

Emergence of Influenza A Viruses in HumansEmergence of Influenza A Viruses in Humans

H1H1

H1H1H3H3

H2H2

H7*H7*

H5*H5*

H9*H9*

19181918

Flu H1N1Flu H1N1

19571957

Flu H2N2Flu H2N2

1968 1968

Flu H3N2Flu H3N2

1980 1996 20021980 1996 2002

1997 2003-2006 1997 2003-2006

1915 1925 1935 1945 1955 1965 1975 1985 1995 2005 20061915 1925 1935 1945 1955 1965 1975 1985 1995 2005 2006

* Avian Flu* Avian Flu

2003 2004

2003 2004

1998 1999

2003

1998 1999

2003

19771977

Moderate (1957-like) Severe (1918-like)

Illness 90 million (30%) 90 million (30%)

Outpatient medical care 45 million (50%) 45 million (50%)

Hospitalization 865,000 9, 900,000

ICU care 128,750 1,485,000

Mechanical ventilation 64,875 745,500

Deaths 209,000 1,903,000

Estimates of Impact of an Influenza Pandemic

Estimates of Impact of an Influenza Pandemic

Avian Influenza A (H5N1):Why is Concern So High?Avian Influenza A (H5N1):Why is Concern So High?

•Lethal to poultry and other mammals

•Present in healthy waterfowl - shed in feces

•Has had (and could have greater) major economic impact

•Lethal to poultry and other mammals

•Present in healthy waterfowl - shed in feces

•Has had (and could have greater) major economic impact

Impact on Animals and EconomyImpact on Animals and Economy

Human Acquisition of H5N1

Human Acquisition of H5N1

Avian Influenza A (H5N1):Why is Concern So High?Avian Influenza A (H5N1):Why is Concern So High?

• Has caused severe disease in humans who have become infected

• Limited human-to-human transmission in Southeast Asia• Could evolve to become readily transmissible in humans• No human H5N1 vaccine commercially available• Limited supply of expensive antiviral medicines of

unknown value in managing pandemic

• Has caused severe disease in humans who have become infected

• Limited human-to-human transmission in Southeast Asia• Could evolve to become readily transmissible in humans• No human H5N1 vaccine commercially available• Limited supply of expensive antiviral medicines of

unknown value in managing pandemic

Direct Impact on HumansDirect Impact on Humans

Control and Prevention of Influenza in Individuals,

Households, and Workplaces

Control and Prevention of Influenza in Individuals,

Households, and Workplaces

•Vaccines

•Anti-virals

•Transmission Interventions (Infection Control)

•Contact Interventions (Social Distancing)

•Vaccines

•Anti-virals

•Transmission Interventions (Infection Control)

•Contact Interventions (Social Distancing)

Tools for Control and Prevention of InfluenzaTools for Control and

Prevention of Influenza

Influenza TransmissionInfluenza Transmission

Leave original hostLeave original host

Survive in transit Survive in transit

Delivered to a susceptible host Delivered to a susceptible host

Reach a susceptible part of the hostReach a susceptible part of the host

Escape host defensesEscape host defenses

Multiply and cause tissue damageMultiply and cause tissue damage

Viruses:Viruses:

Infection Control / Social Distancing Measures

Infection Control / Social Distancing Measures

• Transmission Interventions (Infection Control)

• Facemasks

• Cough etiquette

• Hand hygiene

• Isolation of ill, quarantine of exposed

• Contact Interventions (Social Distancing)

• School closure

• Cancellation of mass gatherings

• Alternatives to face-to-face contact at work

• Increasing distance, decreasing contacts

• Transmission Interventions (Infection Control)

• Facemasks

• Cough etiquette

• Hand hygiene

• Isolation of ill, quarantine of exposed

• Contact Interventions (Social Distancing)

• School closure

• Cancellation of mass gatherings

• Alternatives to face-to-face contact at work

• Increasing distance, decreasing contacts

Evidence for Benefits of Physical Separation

Evidence for Benefits of Physical Separation

• Proximity of less than 3 feet has been associated with increased risk for transmission of infections via respiratory droplets.

New Engl J Med

1982;307:1255-7

Am J Med

1948;4:690

• Proximity of less than 3 feet has been associated with increased risk for transmission of infections via respiratory droplets.

New Engl J Med

1982;307:1255-7

Am J Med

1948;4:690

Distance between chairs

Percentage of carriers or cases

<102 cm 27% (20/73)*

>102 cm 7% (5/71)**P=0.0001 for the difference

Prevention of Contact Transmission

Prevention of Contact Transmission

Influenza viruses are enveloped.

Effectively inactivated by:•Detergents

•Alcohol products

•Bleach

•Household disinfectants

Influenza viruses are enveloped.

Effectively inactivated by:•Detergents

•Alcohol products

•Bleach

•Household disinfectants

Evidence for Benefits of Hand Hygiene

Evidence for Benefits of Hand Hygiene

• Hand hygiene reduces the respiratory infections in healthcare and community settings.

Among Navy recruitsAm J Prev Med 2001;21:79-83

• Handwashing program implemented at a Navy training center.

• 45% reduction in outpatient visits for respiratory illness.• Frequent hand washers had fewer respiratory illnesses.

• Hand hygiene reduces the respiratory infections in healthcare and community settings.

Among Navy recruitsAm J Prev Med 2001;21:79-83

• Handwashing program implemented at a Navy training center.

• 45% reduction in outpatient visits for respiratory illness.• Frequent hand washers had fewer respiratory illnesses.

Among students in residence hallsAJIC 2003;31:364-70Among students in residence hallsAJIC 2003;31:364-70

• College dorms were randomized to having alcohol hand rubs in various locations vs. not.

• Hand rub groups had:

• 14.8%-39.9% reduction in respiratory illnesses

• 43% fewer sick days

• College dorms were randomized to having alcohol hand rubs in various locations vs. not.

• Hand rub groups had:

• 14.8%-39.9% reduction in respiratory illnesses

• 43% fewer sick days

Evidence for Benefits of Hand Hygiene

Evidence for Benefits of Hand Hygiene

Protecting the WorkplaceProtecting the Workplace

Exclude sources of infection.

•Screen and exclude individuals with fever or respiratory symptoms.

•Exclude individuals with ill household members.

Prevent transmission within the workplace.

•Optimize hand hygiene.

•Facilitate respiratory etiquette.

•Maintain environmental hygiene.

Exclude sources of infection.

•Screen and exclude individuals with fever or respiratory symptoms.

•Exclude individuals with ill household members.

Prevent transmission within the workplace.

•Optimize hand hygiene.

•Facilitate respiratory etiquette.

•Maintain environmental hygiene.

Control of Pandemic Influenza in Communities

Control of Pandemic Influenza in Communities

• Failed containment may still delay international spread by 1 month

• Severe travel restrictions may delay U.S. cases by 1-4 weeks

• Border screening difficult because persons may transmit infection for up to a day before they develop illness

• Failed containment may still delay international spread by 1 month

• Severe travel restrictions may delay U.S. cases by 1-4 weeks

• Border screening difficult because persons may transmit infection for up to a day before they develop illness

Without intervention, expect international spread in 1 month and U.S. cases in 1 to 2 months.

Without intervention, expect international spread in 1 month and U.S. cases in 1 to 2 months.

Containment May Be PossibleContainment May Be Possible

A 1918 Pandemic Today Would Exact a Horrible Toll

A 1918 Pandemic Today Would Exact a Horrible Toll

Severe Pandemic (1918-like)

Illness 90 million (30%)

Outpatient medical care 45 million (50%)

Hospitalization 9, 900,000

ICU care 1,485,000

Mechanical ventilation 745,500

Deaths 1,903,000

• 50% or more of those who become ill will seek medical care• 50% or more of those who become ill will seek medical care

HHS Pandemic Influenza Doctrine: Saving Lives

HHS Pandemic Influenza Doctrine: Saving Lives

•Prevent or at least delay introduction into the United States

•May involve travel advisories, exit or entry screening

•For first cases, may involve isolation / short-term quarantine of arriving passengers

•Prevent or at least delay introduction into the United States

•May involve travel advisories, exit or entry screening

•For first cases, may involve isolation / short-term quarantine of arriving passengers

HHS Pandemic Influenza Doctrine: Saving Lives

HHS Pandemic Influenza Doctrine: Saving Lives

• Slow spread, decrease illness and death, buy time• Antiviral treatment and isolation for people with

illness• Quarantine for those exposed• Social distancing• Vaccine when available• Local decisions

• Slow spread, decrease illness and death, buy time• Antiviral treatment and isolation for people with

illness• Quarantine for those exposed• Social distancing• Vaccine when available• Local decisions

WeeksWeeks

ImpactImpact PreparedPrepared

UnpreparedUnprepared

Potential Tools in Our ToolboxPotential Tools in Our Toolbox

•Our best countermeasure – vaccine – will probably be unavailable during the first wave of a pandemic

•The supply of antiviral medications is limited

• Infection control and social distancing measures

•Our best countermeasure – vaccine – will probably be unavailable during the first wave of a pandemic

•The supply of antiviral medications is limited

• Infection control and social distancing measures

The WaveThe Wave1. Delay disease transmission and outbreak peak2. Decompress peak burden on infrastructure3. Diminish overall cases and health impacts

1. Delay disease transmission and outbreak peak2. Decompress peak burden on infrastructure3. Diminish overall cases and health impacts

DailyCasesDailyCases

#1#1

#2#2

#3

Days since First CaseDays since First Case

Pandemic outbreak:No interventionPandemic outbreak:No intervention

Pandemic outbreak:With interventionPandemic outbreak:With intervention

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%

Children/Teenagers 29%

Adults 59%

Seniors 12%

DemographicsDemographics

Glass, RJ, et al. Local mitigation strategies for pandemic influenza. NISAC, SAND Number: 2005-7955JGlass, RJ, et al. Local mitigation strategies for pandemic influenza. NISAC, SAND Number: 2005-7955J

SchoolSchool

HouseholdHousehold

WorkplaceWorkplace

Likely sites of transmissionLikely sites of transmission

Who Infects Whom?Who Infects Whom?

Example: How we might minimize impact of a severe pandemic

Example: How we might minimize impact of a severe pandemic

• Closing schools• Keeping kids and teens at home• Social distancing at work and in the community• Isolating ill individuals and voluntary home

quarantine of household contacts• Treating the ill and providing targeted antiviral

prophylaxis to household contacts• Implementing measures in a uniform way as

early as possible during community outbreaks

• Closing schools• Keeping kids and teens at home• Social distancing at work and in the community• Isolating ill individuals and voluntary home

quarantine of household contacts• Treating the ill and providing targeted antiviral

prophylaxis to household contacts• Implementing measures in a uniform way as

early as possible during community outbreaks

Longini: Social Distancing, Close Schools, Treat the Ill, Treat Close Friends and

Families of the Ill

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

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

Date

Death

s R

ate

s /

100,0

00 P

op

ula

tio

n

(An

nu

al

Basis

)Philadelphia

St. Louis

Liberty Loan Parade

Sept 28, 1918

St. LouisSt. Louis

St. Louis

0

2000

4000

6000

8000

10000

12000

14000

Date

De

ath

Ra

te / 1

00

,00

0 P

op

ula

tio

n

(An

nu

al B

as

is) Mayor closes “theaters, moving picture shows,

schools, pool and billiard halls, Sunday schools, cabarets, lodges, societies, public funerals, open air meetings, dance halls and conventions until further notice”

Closing order withdrawn

Estimated attack rate before interventions:

2.2%

Pandemic Influenza Checklists

Pandemic Influenza Checklists

• Provide framework for action

• Move from uncertainty to measured, informed action

• Identify roles and responsibilities of multiple sectors

• Provide framework for action

• Move from uncertainty to measured, informed action

• Identify roles and responsibilities of multiple sectors

Pandemic Influenza ToolkitsPandemic Influenza Toolkits

•Detail “how to” information for actions

•Continuity planning

•Infection control

•Risk communication

•Put information in one place for easy access

•Build on CDC’s science and information

•Detail “how to” information for actions

•Continuity planning

•Infection control

•Risk communication

•Put information in one place for easy access

•Build on CDC’s science and information

E & S Loss Control Executive Forum

An Introduction toSeasonal, Avian andPandemic Influenza

Toby L Merlin, MD

Director, Division of Partnerships and Strategic Alliances

National Center for Health Marketing/CCHIS

November 15, 2006

E & S Loss Control Executive Forum

An Introduction toSeasonal, Avian andPandemic Influenza

Toby L Merlin, MD

Director, Division of Partnerships and Strategic Alliances

National Center for Health Marketing/CCHIS

November 15, 2006