Avian Flu

Avian FluTyler Cymet, DOAssociate Vice President for Medical EducationAmerican Association of Colleges of Osteopathic Medicine

Outline

History of Avian InfluenzaThe hype The reality todayThe sciencePublic Health IssuesConclusion

The Story of Influenza

Flu strains are typically found in many mammals

Birds and swine are common hosts for what ultimately become human flu virusesFlu thrives in winter but virtually disappears in summer

The Story of Influenza

Influenza mutates and moves around the globe.Flu hosts usually develop an immunity to the virus after infection.

The virus thrives!

Flu survives by overcoming seasonal influences and mutating to overcome the immunity in its target population.Individuals who routinely get an annual flu vaccine typically have a higher resistance to emerging flu strains than someone who does not.

Viral Mutation

Minor mutation in flu virus is referred to as “drift”.A much bigger immunologic change (mutation) is referred to as a “shift”.

Viral MutationWhen there is a “Major” shift in the immunologic structure it may result in a pandemic. (occurring every 50-70 years)Pandemic – an infectious disease occurring over a wide geographic area targeting a high percentage of the population

Avian Flu - 2006The current strain of avian flu, H5N1, represents a major shift.When a major shift occurs 50-75 years after the last exposure:

The target population has little or no residual immunityThe entire population is a ripe target allowing a large percentage of the population to be infected in the same year

Avian Influenza

Pathogenicity based on genetic features and/or severity of disease in poultry

Low pathogenic AI (LPAI)H1 to H15 subtypes

Highly pathogenic AI (HPAI)Some H5 or H7 subtypesLPAI H5 or H7 subtypes can mutate into HPAI

The “Spanish Flu” of 1918

60 million people died worldwide500,000 deaths in USA

“Spanish Flu” of 1918 – Pandemic

Young adults did poorlyDeaths were mostly directly due to the viral infection, not due to secondary bacterial infection

“Surge” Hospital - 1918

Mass vaccination facility – 1918

History

1878: First identified case in Italy1924-25: First U.S. casesLow pathogenic avian influenza first identified mid-twentieth century1970’s: Migratory waterfowl carriersOutbreaks in mink, seals and whales

Avian Flu

The “usual” evolutionary path for most human flu strains

Birds usually acquire the influenza virus firstThe virus then will typically mutate to swine herdsUltimately the virus may then mutate into a form transmissible between humans.

Most new human strains arise in areas with dense human and swine populations, with a lot of human-swine contactThe swine version usually makes the disease a little more “mellow” for the next (human) host

Evolutionary path (cont.)

The transition through swine usually confers “typical” infection characteristics creating:

a self limiting disease, withMortality limited to the younger and older populationsMost deaths due to secondary bacterial infection

Avian Flu Medications

Currently there is no current vaccine. One company has reported some recent success in developing a vaccineCurrent antivirals have shown some effectiveness

Zanamivir and oseltamivir both act by preventing new viruses from emerging from host cells

Resistance has been seen

Traits of the Current Avian Flu (H5N1 virus)

There has been no passage to the swine population.

Traits of the Current Avian Flu (H5N1 virus)

Passage directly to humans from birds creates a fear that it will result in a high mortality rate:

Target healthy adults – the atypical victim group (19-49 years of age)Current mortality rate of > 50%

This may be an overestimateCurrently it has not mutated to a strain that passes from human to humanIn rare circumstances it has passed from bird to human

Need close and prolonged contact

Avian Flu Dynamics

Migratory Birds like ducks carry the virus from place to placeChicken farms act as multipliers- more cases in a small space with lots of contact with humans

Morbidity/Mortality

Approaches 100%in commercialpoultry flocks

Deaths within 2 to 12 days after first signs of illness

Survivors inpoor condition

The Game PlanDetect “bad” flu early

Surveillance is currently being done by the World Health Organization, Center for Disease Control, and various public health agencies.

Stopping the spread of the virus will be critical and is achieved by restricting travel, cancelling public events, engaging in social distancing and keeping people at home.

The Game PlanForm a ring around every patient by limiting contact and treating everyone who came in contact with the patient.De-populate local poultry flocks“Buy” time, vaccinate if available

Avian Influenza Pandemic(Dr. Donald A Henderson)� A moderate disruption for 16 weeks� Maximum of 15% of people ill at any onetime� No advantage to quarantine or “sociallyisolate” people� No need to close universities� Not enough ventilators, hospital beds, ormedical personnel for everyone who mightneed care

The Hype

“We are overdue”“We are unprepared”“Avian flu pandemic is inevitable”“We are helpless”“Oseltamivir (antiviral) is the solution”

Are we overdue?

There is no strict time coursePandemics occur once or twice a century but not with predictabilityMany scares have failed to materialize

Is pandemic inevitable?

It may happenWe can’t say no it won’t happen

What Should We Do?

There is much we can do to slow a pandemic

Clinical Signs

Incubation period: 3-14 days Birds found deadDrop in egg productionNeurological signsDepression, anorexia, ruffled feathersCombs swollen, cyanoticConjunctivitis and respiratory signs

Diagnosis

Clinically indistinguishable from virulent Newcastle DiseaseSuspect with:

Sudden deathDrop in egg productionFacial edema, cyanotic combs and wattlesPetechial hemorrhages

Virology and serology necessary for definitive diagnoses

Diagnosis

Laboratory TestsHP AI is usually diagnosed by virus isolation

Presence of virus confirmed byAGIDELISART-PCR

Serology may be helpful

Differential Diagnosis

Virulent Newcastle diseaseAvian pneumovirusInfectious laryngotracheitisInfectious bronchitisChlamydiaMycoplasmaAcute bacterial diseases

Fowl cholera, E. coli infection

Clinical Signs in Humans

1997: Hong Kong (H5N1)Fever, respiratory, vomiting, diarrhea, pain Fatal cases: severe bilateral pneumonia, liver dysfunction, renal failure, septic shock

1979: MP AI in harbor seals (H7N7)Conjunctivitis in humans in contact

Clinical Signs in Humans

2003: Netherlands (H7N7)ConjunctivitisMild influenza or respiratory symptoms Fatal case: acute respiratory distress syndrome

2004-2005: S.E. Asia, EurAsia

Avian Influenza Vaccine

Traditional killed vaccines are effectiveVaccines will protect only against other avian influenza viruses withthe same hemagglutinin (H) type.

Economic Impact

1983: U.S. outbreak (H5N2) $65 million in lossesDestruction of 17 million birds30% increase in egg prices

1999-2000: Italy outbreak (H7N1)$100 million in compensation to farmers18 million birds destroyedIndirect losses of $500 million

Economic Impact

1997: Hong Kong outbreak (H5N1)$13 million for depopulation and indemnities1.4 million birds

2001: Hong Kong outbreak (H5N1)

1.2 million birds$3.8 million

Economic Impact

2003: European outbreak (H7N7)Over 33 million birds destroyed¼ of Netherlands’ poultry stockCost?

2003-2004: SE Asia (H5N1)8 countries>100 million birds destroyedCost?

2004-2005: SE Asia and EurasiaSpread to Eurasia by migratory birds

Is oseltamivir the solution?

No, it will also take a concerted public health effort

Federal Planning

The federal government has created a federal response plan as of 11/1/2005.

The most recent federal proposal provides money for

Better surveillanceExpanded vaccine and medication suppliesSpecialized Pandemic Plans

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Steps “YOU” can take

Practice good personal hygiene:Avoid hand contact with your mouth, eyes, and nose;Wash hands regularly and often with soap and water;Carry a supply of hand sanitizing gel – use it regularly after visiting a public restroom;Use paper towels to turn off the faucet and open the restroom doors;Cover your mouth when you cough;

Steps “YOU” can take (cont.)

Get a flu shot when offeredWhen flu season arrives avoid contact with infected persons, limit social interactionsBe cognizant in public of potentially infected surfaces;Disinfect commonly used surfaces regularly including phones, desktops, keyboards, countertops, etc. Aerosol sanitizers are available.Don’t loan your phone or laptop to others

Steps “YOU” can take (cont.)

Consider the wearing of an N95 respirator and/or disposable gloves when going out in public;Set aside a supply of food to limit your need to eat in public;Maintain a supply of electrolyte drinks such as Gatorade to combat dehydration should you get the fluStay informed – information on the status of avian flu is available on a number of websites

Steps “YOU” can take (cont.)

When you are in public be aware of potential health issues such as the glass of water that is served but the server has their fingers on the inside or rim of the glass.Avoid the use of public pay phones and be alert to other surfaces in public which may be contaminated – check out counters, door knobs, handshakes.Commons sense will go a long way to eliminating many of the potential sources for you to get the flu.

In Conclusion

Avian flu is currently a bird diseaseWith a lot of potential

There is no need to panicBut it is worthy of more planning

Internet Resources

World Organization for Animal Health (OIE)

www.oie.intUSAHA Foreign Animal Diseases – “The Gray Book”

www.vet.uga.edu/vpp/gray_book/indexWorld Health Organization

www.who.int

Additional Resources

CDC – Centers for Disease Control and Prevention

Avian influenza (bird flu) home pagewww.cdc.gov/flu/avian

U.S. Department of AgricultureBiosecurity for the birds

www.aphis.usda.gov/vs/birdbiosecurityAvian influenza

www.aphis.usda.gov/vs/birdbiosecurity/hpai.html