Cymet, Tyler - lecture avianflu3 16 09_Tyler.pdf · zFowl cholera, E. coli infection. Clinical...
Transcript of Cymet, Tyler - lecture avianflu3 16 09_Tyler.pdf · zFowl cholera, E. coli infection. Clinical...
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