bird flu by dr nayak

7/31/2019 Bird Flu by Dr Nayak

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COLLEGE OF VETERINARY & ANIMAL SCIENCES,BIKANER DEPARTMENT OF VETERINARY PUBLIC HEALTH

Bird fluSUBMITTED TO :-

Dr. (Mrs) Rajani Joshi By:-ME

What is influenza?An acute illness resulting from infection by an influenza virusHighly infectiousCan spread rapidly from person to personSome strains cause more severe illness than others

Bird flu (also called avian influenza, avian flu, bird influenza, or grippe of the birds)Virology

Influenza Types Hosts

Type A Humans, birds, pigs and horses

Type B Humans only

Type C Humans only

Influenza A (H5N1)Children and young adultsAbdominal symptoms commonDiarrhoeaVomitingAbdominal painPneumoniaLymphopenia

Deranged LFTs


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Classification of influenza virusesHaemagglutinin (H) glycoprotein enables virus to attach to host cell15 exist in natureH1, H2 and H3 most commonly associated with human infection

Neuraminidase (N) glycoprotein enzyme essential for virus replicationenables new virion to be released from host cellN1 and N2 most commonly associated with human infection

ChangeInfluenza A viruses undergo frequent changes in their surface antigens or proteinsMinor changes - antigenic drift EpidemicsMajor changes - antigenic shift Pandemics

Antigenic driftOccurs among influenza A viruses resulting in emergence of new variants of prevailing strains everyyearNew variants result in seasonal flu each winterSome years are worse than others partly related to degree of drift

Antigenic shiftMajor changes in surface antigens of influenza A virusesBy mutation or by reassortment between viruses Changes more significant than driftCreating a virus that is markedly different from recently circulating strainsPandemic potential

Antigenic shiftOccurs in two ways: Sudden adaptive change during replication of a normal virus OR From an exchange of genes between human strain of an influenza A virus and an animal strain


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Antigenic shiftGenetic exchange or re -assortment produces a new virus capable of causing a pandemic in humansCan occur when an animal becomes infected with human and animal flu virus at the same time

Antigenic shiftPopulation will have little or no immunity to new virus:Lack of immunity allows virus to spread more rapidly and more widely than ordinary flu viruses

Antigenic drift and shift Drift - 2003 From Influenza A (H3N2), Panama strainTo Influenza A (H3N2), Fujian strainShift - 1957From Influenza A (H1N1) variantsTo Influenza A (H2N2) Asian flu


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SYMPTOMSMild bird flu symptoms

Ruffled feathersReduced egg productionMinor respiratory disease

Severe bird flu symptomsSerious respiratory diseaseAttacks multiple organs and tissuesMassive internal haemorrhaging

Uncomplicated influenzaIncubation 2-4 daysAbrupt onset fever38-40CPeak within 24 hours

3 day durationDry coughResolves in 7 daysCough, weakness, fatigue may persist for weeks

Range of symptomsCough (~85%)Malaise (~80%)Chills (~70%)Headache (~65%)Anorexia (~60%)Coryzal symptoms (~60%)

Myalgia (~53%)Sore throat (~50%)

Complications of influenzaWorsening of existing medical conditionInfluenza-related pneumoniaPrimary viralSecondary bacterialMixed viral-bacterial pneumoniaECG changesMyositisCNS

PREVENTION & CONTROL


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VaccineNot yet

Antivirals (Tamiflu)RocheCapacityGeneric licenceCipla1million 10-capsule courses per month by July

Vaccine 1Potential vaccine since 2004Problem of productionPredicted 900 million doses in 6 months15 micrograms (normal flu dose)However would need at least 2 dosesTrial in 2004

2 x 90 microgram dosesSo, 75 million only

Vaccine 2Vaccine boostingAdjuvantVaccine against relatives of H5Adjuvant2 x 1.9 microgramsVaccine companies not determining the lowest dose acceptably immunogenic

PUBLIC HEALTH IMPORTANCEUnderstanding pandemic

Epidemic : serious outbreak in a single community, population or regionPandemic : epidemic spreading around the world affecting hundreds of thousands of people,across many countries

History of Influenza412 BC - first mentioned by Hippocrates1580 - first pandemic described1580 - 1900 - 28 pandemics

What is a flu pandemic?Flu pandemics are global epidemics of a newly emerged strain of flu (a new influenza A subtype)1918-9 more lives lost than during the First World War


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Circulating Influenza strains

Prerequisites for a pandemicNovel virus subtypeImmunological naivety

Replicate and cause diseaseTransmission between humansH5N1 fails this test, BUTMutationReassortment could do the trick

Who is at risk?Everyone is at riskCertain groups may be at greater riskUntil the virus starts circulating we will not know for sure who is at most risk

Lessons from past pandemicsUnpredictable, not always in winterGreat variations in mortality, severity, pattern of illness or age affectedRapid surge in number of cases over brief period of time, often measured in weeksTend to occur in waves

Key lesson - unpredictability

Pandemic wavesPast experience teaches us that following

the emergence of a new pandemic virus:More than one wave of influenza is likelyGaps between the waves may be weeks or monthsSubsequent wave could be worse than the first

Impact of a pandemic25% population may be affectedHospital admissionsAcute respiratory infectionsAdmissions increase by 50%, at least20,000 new admissions per week, at peak25% of the workforce will take 5-8 working days off

Absenteeism

bird flu by dr nayak

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