1. E & S Loss Control Executive Forum
An Introduction to
Seasonal, Avian and
Pandemic Influenza
Toby L Merlin, MD
Director, Division of Partnerships and Strategic Alliances
November 15, 2006
[Presenters: Please note current slide date on title slide to be sure you are using the most up-to-date slide set. The slide set was developed by the Influenza Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention. This slide set is current as of ]

2. Introduction to Influenza
Seasonal, avian, and pandemic
Control measures for individuals, households, and workplaces
Control measures for communities

3. Definition 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
To begin, it’s important to be clear about the definition and symptoms of influenza. Influenza is a contagious disease caused by an RNA virus. It poses both a global infectious disease threat and an annual public health problem. Influenza primarily infects the respiratory tract (nose, throat, and lungs). The disease can cause severe illness and lead to life-threatening complications, such as pneumonia, in many people.

4. Influenza A Viruses Subtyped based on surface glycoproteins
16 hemagglutinins (HA) and 9 neuraminidases (NA)
Current human subtypes: H1N1, H3N2
Segmented genome HA
Influenza A viruses contain surface proteins called hemagglutinins (or HA) and neuraminidases (or NA). Scientists have identified subtypes of influenza viruses based on the genetic arrangement of these HA and NA proteins, as well as other factors. Although the 16 HA and 9 NA proteins may combine in many ways, only 2 subtypes currently spread among humans: H1N1 and H3N2. Technically, other subtypes can infect humans, but they don’t spread from person to person regularly. NA

5. 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
Influenza viruses infect a number of animal species, including birds and mammals. People usually are infected only by specific human influenza viruses that circulate globally throughout the year. People can be infected by influenza A and influenza B viruses. A combination of influenza A and B viruses therefore is included in the annual influenza vaccine people can receive. Influenza A viruses, of particular interest in this presentation, circulate in wild birds and infect both wild and domesticated birds. Wild birds are a primary source for influenza A viruses that infect other species.

6. Avian Influenza A Viruses
Human Influenza
A Viruses
H1 – H16
H1 – H3
Some types of influenza A viruses infect and spread among birds and are called avian viruses. These have demonstrated a capacity to recombine or to change in other ways that enhance their capacity to infect species other than birds, including humans. This will be important to remember we are considering viruses that gain the potential for evolving into a pandemic.

7. Emergence of Influenza A Viruses in Humans
2003
H5*
H7* H1 H3 H2 H1
Many avian influenza viruses that circulate globally could evolve into a strain that could cause a pandemic. There were 3 influenza pandemics during the past century, each with its own characteristics and impacts. Scientists expect influenza pandemics to continue periodically. They can begin anywhere in the world.
1977
1918
Flu H1N1
1957
Flu H2N2
1968
Flu H3N2
* Avian Flu

8. 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)
It’s important to understand that influenza viruses change often. Minor changes, also called “antigenic drift,” occur constantly. That’s why it’s important to be vaccinated annually; scientists try to match the components of each year’s vaccine with predicted circulating strains by using knowledge gained through domestic and global surveillance networks. Sometimes, more radical genetic changes, also called “antigenic shift,” occur, which can result in the emergence of a novel influenza virus in the human population.

9. 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
It is easy to mistake influenza for other infections, such as colds and other viral infections. Although seasonal influenza usually lasts only about a week for many people, it can last longer and can contribute to serious secondary infections, such as pneumonia. People sometimes confuse influenza with “stomach flu” because of the use of “flu” in both terms. “Stomach flu” actually is a general term for gastroenteritis, which results in vomiting and diarrhea – symptoms not usually seen in typical cases of seasonal influenza.

10. Usual Influenza Symptoms
- Fever - Headache
- Fatigue - Dry cough
- Body aches - Runny or stuffy nose
Children also may have gastrointestinal symptoms – nausea, vomiting, or diarrhea
Usual symptoms of seasonal influenza include fever, headache, fatigue, dry cough, body aches, and a runny or stuffy nose. Children also may have gastrointestinal symptoms, such as nausea, vomiting, or diarrhea.

11. How 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
It is thought that the main way influenza viruses are spread from person to person is through transmission of respiratory droplets during coughing and sneezing. Close contact (about 3 feet or less) usually is necessary for this type of spread. Influenza viruses also can spread by touching respiratory droplets on yourself, others, or an object, then touching mucus membranes, such as the mouth, nose, or eyes, without washing contaminated hands.

12. Average 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
In the United States each year, illness from influenza has a major impact on the people’s health and the nation’s economy.

13. Pandemic vs. Seasonal Influenza
Seasonal outbreaks
Caused by subtypes of influenza viruses that already circulate among people
Pandemic outbreaks
Caused by:
New subtypes
Subtypes that have never circulated among people, or
Subtypes that have not circulated among people for a long time
It’s important to understand the differences between seasonal and pandemic influenza. Seasonal influenza outbreaks are caused by influenza virus subtypes that already circulate among people. In contrast, pandemic outbreaks are caused by new subtypes, by subtypes that have never circulated among people, or by subtypes that have not circulated among people for a long time.

14. Three 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
Now, let’s turn to pandemic influenza, which is markedly different from influenza that circulates each year. Three factors are necessary for an influenza pandemic to occur: 1) a new influenza A virus must emerge in the human population; 2) the virus must cause serious illness in humans; and 3) the virus must spread easily from person to person.

15. 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
Although seasonal influenza is a serious disease that causes many illnesses and deaths each year, an influenza pandemic can have both immediate and long-term consequences to people in the United States and around the world.

16. Emergence of Influenza A Viruses in Humans
2003
H5*
H7* H1 H3 H2 H1
Many avian influenza viruses that circulate globally could evolve into a strain that could cause a pandemic. There were 3 influenza pandemics during the past century, each with its own characteristics and impacts. Scientists expect influenza pandemics to continue periodically. They can begin anywhere in the world.
1977
1918
Flu H1N1
1957
Flu H2N2
1968
Flu H3N2
* Avian Flu

17. Estimates of Impact of an Influenza Pandemic
Moderate (1957-like)
Severe (1918-like)
Illness
90 million (30%)
Outpatient medical care
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

18. Avian Influenza A (H5N1): Why is Concern So High?
Impact on Animals and Economy
Lethal to poultry and other mammals
Present in healthy waterfowl - shed in feces
Has had (and could have greater) major economic impact
Avian influenza A (H5N1) strains currently circulating in many countries and Asia and spreading into Europe have a number of factors that are causing growing concern among scientists. Influenza H5N1 is having a major impact on animals and on the economies of affected countries.

19. Human Acquisition of H5N1

20. Avian Influenza A (H5N1): Why is Concern So High?
Direct Impact on Humans
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
Avian influenza A (H5N1) strains also have caused severe disease in some humans, primarily through close or direct contact with poultry or other domesticated. The potential for the strains to mutate (reassort) through combination with other human influenza strains is a great concern, because such a change could produce a virus that would be both highly pathogenic and easily transmissible among humans.

22. Control and Prevention of Influenza in Individuals, Households, and Workplaces
[Presenters: Please note current slide date on title slide to be sure you are using the most up-to-date slide set. The slide set was developed by the Influenza Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention. This slide set is current as of ]

23. Tools for Control and Prevention of Influenza
Vaccines
Anti-virals
Transmission Interventions (Infection Control)
Contact Interventions (Social Distancing)

24. Influenza Transmission
Viruses:
Leave original host
Survive in transit
Delivered to a susceptible host
Reach a susceptible part of the host
Escape host defenses
Multiply and cause tissue damage

25. 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

26. 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
Distance between chairs
Percentage of carriers or cases
<102 cm
27% (20/73)*
>102 cm
7% (5/71)*
*P= for the difference

27. Prevention of Contact Transmission
Influenza viruses are enveloped.
Effectively inactivated by:
Detergents
Alcohol products
Bleach
Household disinfectants

28. Evidence for Benefits of Hand Hygiene
Hand hygiene reduces the respiratory infections in healthcare and community settings.
Among Navy recruits
Am 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.

29. Among students in residence halls AJIC 2003;31:364-70
Evidence for Benefits of Hand Hygiene
Among students in residence halls AJIC 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

30. Protecting 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.

31. Control of Pandemic Influenza in Communities

32. Containment May Be Possible
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
Border screening difficult because persons may transmit infection for up to a day before they develop illness

33. Would Exact a Horrible Toll Severe Pandemic (1918-like)
A 1918 Pandemic Today
Would Exact a Horrible Toll
50% or more of those who become ill will seek medical care
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

34. 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 Slow Down Introduction in the United States
Right now there are two primary goals for public health systems:
To prevent or delay entry of a novel virus with pandemic potential by
imposing travel advisories and possibly some travel restrictions;
establishing medical screening at points of departure from foreign ports and points of arrival in the United States;
isolating ill passengers who appear to be infected with the novel virus
quarantining, on a short-term basis, other passengers who may have been exposed to such ill travelers
Preparedness has to occur in locally. All communities should be involved.

35. 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
Unprepared
2. To slow the spread of infection within the United States by quickly identifying cases and instituting pharmaceutical and non-pharmaceutical interventions, including
Isolation procedures for the sick (stay home, school closures, other social measures)
Proper utilization of medical resources
Use of current antivirals for treatment, not prevention
Vaccine production to prevent illness
In addition to these two public health system goals, the Federal Government has identified a third goal to:  
sustain infrastructure and mitigate impact to the economy and the functioning of society
Impact
Prepared
Weeks

36. Potential 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

37. The Wave 1. Delay disease transmission and outbreak peak
2. Decompress peak burden on infrastructure
3. Diminish overall cases and health impacts
Daily
Cases #1 #2 #3
Days since First Case
Pandemic outbreak:
No intervention
With intervention

38. Who Infects Whom? Likely sites of transmission Children/Teenagers 29%
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
Likely sites of transmission
Children/Teenagers %
Adults %
Seniors %
School
Household
Workplace
Demographics
Glass, RJ, et al. Local mitigation strategies for pandemic influenza. NISAC, SAND Number: J

39. 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

40. Longini: Social Distancing, Close Schools, Treat the Ill, Treat Close Friends and Families of the Ill

41. Weekly mortality data provided by Marc Lipsitch (personal communication)

42. Liberty Loan Parade Sept 28, 1918

43. St. Louis 2.2% Estimated attack rate before interventions:
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

44. Pandemic Influenza Checklists
Provide framework for action
Move from uncertainty to measured, informed action
Identify roles and responsibilities of multiple sectors

46. Pandemic 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
We continue to talk with people from business, education, healthcare, faith- and community-based organizations to refine our understanding of their particular assets and challenges.
The Tool Kit will be Web-based so that we can update information and resources as we continually learn more about pandemic influenza. In addition, this format enables us to provide interactive support such as Webinars, on-line chats, and a venue for users to submit best practices and lessons learned.

48. E & S Loss Control Executive Forum
An Introduction to
Seasonal, Avian and
Pandemic Influenza
Toby L Merlin, MD
Director, Division of Partnerships and Strategic Alliances
National Center for Health Marketing/CCHIS
November 15, 2006
[Presenters: Please note current slide date on title slide to be sure you are using the most up-to-date slide set. The slide set was developed by the Influenza Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention. This slide set is current as of ]