Influenza, commonly known as "the flu", is an infectious disease caused by an influenza virus. Symptoms can be mild to severe. The most common symptoms include: high fever, runny nose, sore throat, muscle and joint pain, headache, coughing, and feeling tired.

1. Lecturer
Dept of swasthavritta
GAAC, Ahmedabad
Vd Rakesh Shukla, GAAC, Ahmedabad

2. O Influenza occurs worldwide. Influenza can occur
in Pandemics.
O Influenza virus undergoes antigenic variation
from time to time.
O It is an acute respiratory tract infection caused by
influenza virus, of which there are 3 types – A, B
and C. all known pandemics were caused due to
influenza A strains.
O The disease is characterized by sudden onset of
chills, malaise, fever, muscular pains and cough.
Vd Rakesh Shukla, GAAC, Ahmedabad

3. Agent factors
O A) Agent : Family – Orthomyxoviridae
O There are 3 subtypes Influenza virus A, B and C.
O Both A and B viruses has 2 surface antigens – the
haemagglutinin (H) and the nuraminidase (N). The H antigen
initiates infection following attachment of the virus to the
susceptible cell. The N antigen is responsible for the release of
the virus from the infected cell.
O The antigens of Influenza A virus frequently change.
O If the change is sudden and major change it is called antigenic
‘shift’ (can lead to pandemic).
O If the change is gradual and minor it is called antigenic ‘drift’.
Vd Rakesh Shukla, GAAC, Ahmedabad

4. b) Reservoir of infection: exists in animals and
birds
c) Source of infection: usually case or sub clinical
case.
d) Period on infectivity: present in the naso
pharynx from 1- 2 days before and 1 – 2 days
after the onset of symptoms.
Vd Rakesh Shukla, GAAC, Ahmedabad

5. Host factors
O Age and sex: all ages and both sexes.
O Human mobility: important factor in the spread
in of infection.
O Immunity: specific immunity.
Incubation period
18 – 72 hrs.
Vd Rakesh Shukla, GAAC, Ahmedabad

6. Environmental factors
O Season – epidemics usually occur in winter
months and in rainy seasons. But in india at
summer seasons.
O Over crowding – enhances transmission.
Modes of transmission
O Person to person by droplet infection or droplet
nuclei created by sneezing, coughing or talking.
The portal entry of the virus the respiratory tract.
Vd Rakesh Shukla, GAAC, Ahmedabad

7. Pathogenesis and clinical features:
O The virus enters the respiratory tract and causes
inflammation and necrosis of the superficial
epithelium of the tracheal and bronchial mucosa,
followed by secondary bacterial invasion.
O There is no viraemia. Fever chills, aches, pain,
coughing and generalized weakness.
O The most dreaded complication is Pneumonia,
which should be suspected if fever persists beyond
4-5 days or recurs abruptly after convalescence.
Vd Rakesh Shukla, GAAC, Ahmedabad

8. Laboratory diagnosis
a) Virus isolation – through nasopharyngeal
secretion obtained by indirect fluorescent
antibody technique
b) Paired sera – serum taken as early as
possible in acute phase of the disease(not
later than 5th day) and another taken 10-14
days after the onset i.e. convalescent stage
of the illness.
Vd Rakesh Shukla, GAAC, Ahmedabad

9. Prevention of influenza
O Good ventilation of building,
O Avoidance of crowded places during
epidemics, encouraging suffers to cover their
faces with handkerchief when coughing and
sneezing.
O To stay at home at the first sign of influenza
are all sensible precautions.
Vd Rakesh Shukla, GAAC, Ahmedabad

10. Prevention and control of Influenza
O Primary prevention
O Influenza vaccination
O Avoid close contact with patients
O Due to genetic changes occurring in the virus
vaccine have to prepared from latest strains
every year.
Vd Rakesh Shukla, GAAC, Ahmedabad

11. Secondary prevention
O Early diagnosis and treatment
O Since antiviral drugs are not available give
symptomatic treatment to prevent complications
and death
Vd Rakesh Shukla, GAAC, Ahmedabad

12. Influenza vaccines
O A) Killed vaccines administered by the subcutaneous or
intramuscular route.
O A single inoculation : 0.5ml for adults and children over 3
years and 0.25 ml for children from 6 months to 36 months
of age
O A killed vaccines can produce fever, local inflammation at
the site of infection and very rarely Gullian Barre syndrome
( an ascending paralysis). Since the vaccines strains are
grown in eggs, persons allergy to eggs may develop signs
of hypersensitivity.
Vd Rakesh Shukla, GAAC, Ahmedabad

13. b) Live attenuated vaccines
May be administered as nose drops into the respiratory
tract . They stimulate local as well as systemic
immunity.
c) Newer vaccines –
i) Split vaccines - known as sub-virion vaccine. A
highly purified vaccines, producing fewer side
effects the whole virus vaccines
ii) Neuraminidase – Specific vaccines – it includes N
antigen of the prevailing influenza virus.
iii) Recombinant vaccines – by recombinant technique.
Vd Rakesh Shukla, GAAC, Ahmedabad

14. Public health importance
O Because of change in the antigen of the virus
immunity will not be effective against the new virus
O A new vaccine has to be created each time an
antigenic change occurs in the virus
O People have to be given a new vaccine when the
virus changes
O Creating a new vaccine in a short time is difficult
Vd Rakesh Shukla, GAAC, Ahmedabad

15. Influenza virus
Vd Rakesh Shukla, GAAC, Ahmedabad

16. Thank you
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Vd Rakesh Shukla, GAAC, Ahmedabad