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MIC1IEP
Topic 12 Influenza
26th May 2016
ANNA MORRIS
ROOM 310
THOMAS CHERRY BUILDING
PH: 9479 1501
Influenza : Orthomyxoviruses
Respiratory Tract Infection
Systemic rather than localised infection of
the respiratory tract and lungs
Transmission via droplets or fomites
Seasonal more common in winter
months & also in spring
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Influenza Virus
WHO: Annual epidemics cause 250,000
500,000 deaths worldwide
Vaccine preventable disease (Aust Govt -NNDSS)
71,528 cases Australia wide in 2015 ytd
67,757 cases in 2014
ad
campaigns
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Notifiable disease
Communicable disease
Required by law to be reported to the Health
Authorities
Infectious disease that is transmitted
readily from one individual to another
usually in normal everyday activities
Symptoms of Influenza
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How far do your droplets travel
in a sneeze?Brock Biology of microorganisms
100mph
30 feet = 9 metres
Myth busters
17 and 13 feet 4 5 metres
Either way, its a long way!!
Influenza types
Influenza type A
Humans, birds, animals
Epidemics and pandemics
Influenza type B
Humans
epidemics
Influenza type C
Mild respiratory infection
Not assoc with epidemics or pandemics
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Influenza A virusIcosahedral
Enveloped
Negative sense
ssRNA
~ 500 spikes or
projections
Hemagglutinin (HA) 4 x more than NA
Neuraminidase (NA)
Envelope carries Hemagglutinin and NeuraminidaseHemagglutinin assists with attachment
Neuraminidase assists in liberation of mature viruses from host cells
Influenza Envelope
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Replication cycle of Influenza A
virus
Influenza type A
Only A is subtyped
Typed according to surface glycoprotein
antigens
Hemagglutinin
Neuraminidase
18 H and 11 N recognized & named
accordingly
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The 2015 Southern Hemisphere influenza
season vaccine strains
A/California/7/2009 (H1N1)pdm09 - like virus
A/Switzerland/9715293/2013 (H3N2) - like virus
B/Phuket/3073/2013 like virus (Yamagata
lineage)
The Australian Influenza Vaccine Committee
(AIVC) selected influenza viruses for the
composition of the trivalent influenza vaccines. Therapeutic Goods Administration accepted the
recommendations of the AIVC.
Glycoproteins Haemagglutinin and
Neuraminidase
Type of H or N depending on which type of
each expresses
A/California/7/2009 (H1N1)pdm09 - like
virus
A/Switzerland/9715293/2013 (H3N2) - like
virus
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Resistance to reinfection??
Infected individuals will produce antibodies
to both H and N antigens
Lack of resistance to Flu from season to
season is due to mutation in surface
antigens
Mutation due to antigenic shift and drift Drift: small and constant
Shift: sudden and major
Only seen in Influenza type A
Results in pandemics due to new strain
Influenza : Five major pandemics
Spanish flu
1918
(H1N1)
20 50 million deaths
Asian FluH2N2
1957
2 million deaths
Hong Kong Flu
H3N2
1968
1 million deaths
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Influenza : Five major pandemics
Russian flu
1977
(H1N1)
17,000 deaths
Swine Flu
2009
H1N1
18,500 deathsSwine origin
Pandemic lasted until August 2010
Transmission
Droplet transmission
Inhalation
Fomites
Virus survival is high (many hours) outside
the body
Surfaces
Cloths, tissues
Infective period immediately prior to
signs and symptoms for up to 7 days after
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Infectious Droplets & Droplet
Nuclei Travel Lengths
Duck for cover!!
PathogenesisEntry via respiratory tract
Attachment to respiratory epithelial cells H spikes
Asymptomatic infection common
Mild infection possible
Cold-like infectionSymptoms appear 1 3 days following infection
Fever, chills, malaise, muscle pain
Due to release of cytokines from damaged cells & infiltrating leukocytes
Virus spread
Runny nose
Sore throat
Dry cough
Infection may increase in severity
Results in bronchitis or pneumonia
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PathogenesisRecovery
1 3 weeks
Unless progresses to more severe infection
Infective period starts before symptoms appear
Shedding of virus from this stage for a week
Death most common in:
elderly
Immunocompromised
2 0 bacterial infection most likely cause
Eg Pneumonia
Exacerbation of pre-existing chronic cardiac or respiratory illness
Predisposing factors
Impaired Immunity
Immunocompromised individuals
Age
< 5 - >65 years of agePregnancy
Aborigines & Torres Strait Islanders > 15
years
Medical condition
Heart disease, chronic lung disease
asthma, emphysema,
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Predisposing factors
Homelessness
Nursing home or long term care residents
Pre-existing chronic condition
Obesity, diabetes, alcoholism, kidney disease
Asthma patients who have frequent hospital
visits
Downs syndrome
Vaccination is recommended for high risk individuals
Universal influenza vaccine
Research being conducted into universal
vaccine
Aim is for vaccine to trigger immune
responses against conserved antigens These are viral protein targets that mutate
only slowly
And are also similar among many strains of
influenza viruses
Therefore can generate immune responses
that cross-react among virus strains
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Do I have a cold or the Flu??Flu is not the common cold!!
Flu is more severe
Cold symptoms last from two to a few days
flu lasts up to a week
Flu - high fever
Cold : usually only mild fever
Flu - Muscular pains and shivering attacks
flu usually starts with a dry sensation in the nose andthroat
Colds - runny nose
Flu symptoms onset rapid
Cold symptom onset gradual
ComplicationsMost common in immucompromised
Increases chances of complications and
risk of death
Primary Influenza pneumonia
Difficult breathing, cyanosis
20 bacterial pneumonia
Shortness of breath, green or yellow phlegm, chest
pains, fever
Inflammation of brain or heart
Often assoc with recovery process
Reyes syndrome
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Prevention
Annual immunization
Good personal hygiene
Cover nose and mouth when coughing or
sneezing
Dispose of tissue appropriately
Wash hands after cough or sneeze
Soap & water
Alcohol based hand sanitizer
Avoid touching eyes, nose & mouth
Stay home from work and school
Treatment
Bed & rest until body temp is in normal
range for 48 hours
Drink fluids to maintain normal urine
output
Paracetamol (+/or aspirin in adults) to
control fever, aches & pains
Antiviral treatment to reduce severity &
length of illness
Avoid further damage or challenge of
respiratory tract
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Mucocilliary escalator
Antiviral drugs
Relenza Zanamivir
Tamiflu oseltamivir
Used against both Types A & B Influenza
Act by inhibiting viral neuraminidase
Blocks release of new virus particles being
released from infected host cells
Recommended under severe infection or
in high risk individuals
Effective if treatment commences within
48 hours of symptoms appearing
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Identification/DiagnosisReverse transcription polymerase chain
reaction (RT-PCR) (1 6 hours)
RIDT Rapid Influenza Diagnostic test
Used for Influenza types A & B although not
can distinguish (
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Influenza vaccine manufacture
Avian Flu Influenza type A
Bird Flu
Human infection after virus crosses
species barrier
Usually results after contact with infected
poultry or environments
Human to human contact is rare but does
occur
Different types have been isolated
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H5NI (HPAI Highly pathogenic avian
influenza)
H5N1 causes infection in man and
animals other than poultry, eg domestic
cats and dogs
Highly pathogenic
high incidence of disease & death
wild birds and domestic poultry
HPAI H5N1
first isolated in 1996
farmed goose
Guandong province, China
H5NI (HPAI Highly
pathogenic avian influenza)Followed by outbreaks in 1997
poultry farms & live animal markets
18 humans infected & 6 deaths
Increasingly assoc with infection in
chickens
Culling of commercial poultry flocks
Hong Kong
Effective
Outbreaks in 2003 resulted in infection in over
60 countries
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H5NI (HPAI Highly pathogenic avian
influenza)
Re-emerged in 2003 in birds
Death of 100s of millions of birds
Disease
culling
Re-emerged in humans
630 cases
375 deaths
By June 2013
Infection is with direct contact with birds
rather than human to human transmission
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ReferencesMicrobiology and Infection Control for Health
Professionals. Chapter 19, 6th Ed, Lee &
Bishop.
Chapter 8, Brock Biology of Microorganisms,
14th Ed, 2015
Microbiology and Infection control for Health
professionals. Chapter 19 , Lee & Bishop.
http://www.fda.gov/BiologicsBloodVaccines/ScienceResearch/ucm353397.htm
http://www.medical-supplies-equipment-
company.com/flu-transmission-and-flu-
prevention-576.htm
References
http://www.rapidreferenceinfluenza.com/ch
apter/B978-0-7234-3433-7.50009-
8/aim/influenza-virus-structure
http://www.virology.ws/2009/04/30/structure-of-influenza-virus/
http://www.betterhealth.vic.gov.au/bhcv2/b
hcarticles.nsf/pages/Flu_influenza
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Learning ObjectivesAt completion of this lecture students should
be familiar with:
Some of the basic characteristics & clinicalfeatures of the Influenza virus and the Fludisease
The mode of transmission, pathogenesis,symptoms, treatment and prevention ofInfluenza