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Influenza (The flu)
Presented by:
PoorMontaseri Z, DM
Infectious Diseases and
Tropical Medicine
Fasa University of Medical
Science
Influenza, commonly known as “the flu”, is a
highly contagious infection of the airways caused
by influenza viruses.
 In temperate climates, seasonal
epidemics occur mainly during winter
 In tropical regions, may occur throughout
the year, causing outbreaks more
irregularly.
‫درپاندمي هاي سالهاي‪ )Asian flu ( 1957‬و‬
‫‪ )Hong kong flu( 1968‬نيزبه ترتيب‬
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‫سطح جهان کشته شدهاند‬
The first cases of human infection with
novel H1N1 influenza virus were detected
in April 2009 in San Diego and Imperial
County, California and in Guadalupe County,
Texas.
 The virus has spread rapidly.

Distribution of pandemic H1N1
Distribution of Influenza in Iran
Iran reported an increase in influenza
detections from previous weeks.
 Influenza A(H1N1) viruses were
predominant with some A(H3N2) and B
detections reported.

The Influenza Virus

RNA viruses/ Subfamily: Orthomyxoviridae.

enveloped viruses that may exist in spherical or
filamentous forms of 80 to 120 nm
 Antigenic drift?
◦ Minor change
 Antigenic shift?
◦ Major change
Antigenic
Drift
Point Mutation of Hemagglutinin
and Neuraminidase gene
Antigenic Shift
Human H2N2
Generation of new Human Virus (H3N2)
Possessing Hemagglutinin from Avian Virus (H3N8)
Human H3N2
Genetic Reassortment
Antigenic Shift
Avian H3N8
Survival of Influenza viruses in
Enviroment

Plastic and steels stuffs: more than 24 h

Cloths and papers: 8-12 h

Viable on hands: <5 minutes only at high viral
titers
 In virus classification influenza viruses
are :
 A
Three known A subtypes of influenza viruses
currently circulating among humans (H1N1,
H1N2, and H3N2).



B
C
Type
Host
Humans,
birds,
(seasonal,
horses,
Avian, Swine) other
mammals
A
Clinical
Importa
nce
Pattern of
Subtypes Epidemiology
Occurrence
Moderate
to severe
disease
Sporadic,
epidemics,
pandemics
Yes
H1-H16
Moderate
to severe
disease
Sporadic,
epidemics
No
B (seasonal)
Humans
C
Humans
Mild
and swine disease
Sporadic,
localized
outbreaks
Antigenic shift
/drift
N1-N9
No
Antigenic drift
Antigenic drift
Bridges et al. 2008.
Avian Influenza

Avian influenza is an infectious disease of birds
caused by type A strains of the influenza virus.

Avian influenza transmitted by birds usually through
feces or saliva.

H5N1; the strain of avian flu,
◦ Most cases of avian influenza infection in humans have
resulted from contact with infected poultry
◦ The spread of avian influenza viruses from one ill person to
another person has been reported very rarely
Swine Flu
 Swine influenza (swine flu) is a respiratory disease of
pigs caused by type A influenza virus.
 The main swine influenza viruses circulating in U.S.
pigs in recent years are: H1N1 influenza virus, H3N2
virus, H1N2 virus.
 Disease was more severe among people younger than 65
years of age than in non-pandemic influenza seasons.
 With significantly higher pediatric mortality, and higher
rates of hospitalizations in children and young adults.
H1N1/H5N1
high morbidity
but low
mortality rates
(1%-4%).
The estimated incubation period is unknown
and could range from 1-7 days, and more likely
1-4 days.
Transmission and
Evolution




Influenza virus is transmitted easily from person to person
when speaking, by sneezing or coughing and can be
confused with other severe Influenza illnesses caused by
different viruses.
Adults may be contagious from one day prior to the
commencement of symptoms to up to 7 days after
becoming sick.
Children may be contagious for a period of up to 14 days
after the appearance of symptoms.
Immuno-suppressed more than others.
Relationship between mortality and
involvement age
Attack rates are generally highest in the
young, (children aged 5--14 years)
 whereas mortality is generally highest
among older adults

Symptoms
Flu
Cold
Fever
Usually 80%
Rare
Aches
Severe aches and pains
Occasion slight body aches
Chills
Fairly common (60%)
Uncommon
Tiredness
Moderate to severe
Mild
Sudden symptoms
Sudden often within 3-6h(chills
/aches)
Not sudden develop over a few
days
Cough
Non-productive, dry cough (80%)
Hacking, productive cough
Sneezing
Not commonly present
Commonly present
Stuffy nose
Not commonly present
Common but resolves within 1
week
Sore throat
Can be present
Common due to inflammation
Chest discomfort
Severe, felt along front of body,
neck to abdomen
Mild to moderate
Headache
Very common (80%)
Fairy uncommon
Complication
Pneumonia, can be life threatening
Sinus /ear infection
Complications of Influenza
Pulmonary Complications

◦ primary influenza viral pneumonia and secondary bacterial
infection (Streptococcus pneumoniae and Staphylococcus
aureus)

Other Pulmonary Complications
◦
◦
◦
◦
Bronchiolitis
Croup
Acute exacerbation of chronic bronchitis
Exacerbations of asthma and worsening pulmonary
function in children with cystic fibrosis

Nonpulmonary Complications
◦ Myositis
◦ Cardiac Complications (myocarditis and
pericarditis , myocardial infarction)
◦ Toxic Shock Syndrome
◦ Central Nervous Complications (Guillain-Barré
syndrome, Reye Syndrome)
Diagnosis
Clinical Diagnosis
 Rapid Influenza Diagnostic Tests
 Molecular Diagnostic Tests (nucleic acid

hybridization and PCR)

Serology (complement fixation and hemagglutination
inhibition)

Virus Isolation
Influenza
Type A Influenza Can not be Eradicated

Continous emergence of new virus variant
Prevention:
1.Primary
2.Secondary
Prevention in the Health
Care Setting
Patients with seasonal influenza can generally be managed under droplet
precautions, except when undergoing aerosol-generating procedures,
such as bronchoscopy, sputum induction, elective intubation and
extubation, and autopsies, during which management requires airborne
precautions.
Primary prevention
Vaccination
Flu shot
Inactivated vaccine
Killed virus
Nasal spray flu
vaccine
Live
attenuated
virus vaccine
(LAIV)
www.fightflu.com
Vaccination/ Common side effects include:
 Local reactions at the injection site (soreness, swelling,
redness).
 Possibly some systemic reactions (fever, headache,
muscle or joint aches). these symptoms are mild, self-limited
and last 1-2 days.
 Guillian-Barre syndrome (1/1000000)
Secondary prevention
Watch for emergency warning
signs
Most people should be able to recover at home, but watch for emergency
warning signs that mean you should seek immediate medical care.
In adults:






Difficulty breathing or shortness of breath
Pain or pressure in the chest or abdomen
Sudden dizziness
Confusion
Severe or persistent vomiting
Flu-like symptoms improve but then return with fever and
worse cough
Secondary prevention
Emergency warning signs in
children
If a child gets sick and experiences any of these warning
signs, seek emergency medical care.
In children:
 Fast breathing or trouble breathing
 Bluish or gray skin color
 Not drinking enough fluids
 Severe or persistent vomiting
 Not waking up or not interacting
 Irritable, the child does not want to be held
 Flu-like symptoms improve but then return with fever
and worse
Thanks for
your
attention