2. OBJECTIVES OF THIS SESSION…
INTRODUCTION
EPIDEMIOLOGY
EPIDEMIOLOGICAL DETERMINANTS
MODE OF TRANSMISSION
PATHOGENESIS
CLINICAL FEATURES
TREATMENT AND CHEMOPROPHYLAXIS
PREVENTION AND CONTROL
3. INTRODUCTION
Acute febrile illness.
Mainly affects the Respiratory system
Viral disease (RNA)
Characterized by sudden onset of fever, non specific
respiratory systems such as headache, myalgia and
malaise
Followed by post influenzal asthenia(weakness).
4. EPIDEMIOLOGY
3 PANDEMICS
FIRST PANDEMIC(1918-1919)
it was called SPANISH FLU, caused by
SWINE INFLUENZA VIRUS(H1N1 VIRUS).
50 Millions people affected
about 20 millions were killed(in INDIA 6
millions were killed)
5. SECOND PANDEMIC(1956-1957)
it was called ASIAN FLU, caused by H2N2
VIRUS.
1OOO Millions people affected
about 2.5 millions were affected in INDIA (hardly
767 death noted)
THIRD PANDEMIC(1968)
it was called HONG-KONG FLU, caused
by H3N2 VIRUS.
6.
7. FACTORS FAVORING THE PANDEMICS
Antigenic variation (antigenic shift)
Short incubation period
Droplet infection mode
Universal susceptibility
Immunocompromised individual
Lack of effective vaccine
Lack of knowledge about the fact of virus
during the interepidemic periods
8.
9. AGENT FACTORS
AGENT:
Belongs to group ORTHOMYXOVIRUS
3 forms: TYPE A, TYPE B, TYPE C
The type A and B have 2 antigens
Hemagglutinin(H) antigen
Neuraminidase(N) antigen
H antigen – causes agglutination of erythrocytes, attaches the virus to human
cell
N antigen- responsible for release of newly formed virus from parasitized host
cell
11. TYPES OF VIRUS
TYPE A
Antigenic structure unstable- antigenic variation
change in H antigen –H1,H2, H3 so on..
N antigen–N1, N2, N3 so on..
Cause severe epidemic and pandemic
TYPE B (Children)
No antigenic variation
Not associated with pandemics and epidemics
Localised outbreaks with irregular periodicity
TYPE C
Antigenic structure stable
Do not cause significant disease
12. RESERVOIR:
TYPE A-Man, birds, pigs, horses, water
fowls
TYPE B,C-Only man
INFECTIVE MATERIAL:
Respiratory secretions
PERIOD OF INFECTIVITY:
3-5 days
13. HOST FACTORS
AGE INCIDENCE
Common among children and elderly people
Spanish flu – adults
Asian flu - children
SEX INCIDENCE
Equal in both sexes
IMMUNITY
Antibodies to H antigen:
prevent the initiation of infection by neutralizing the virus
Antibodies to N antigen:
Modifies infection by preventing the release and spread of new virus
14. ENVIRONMENTAL FACTORS
Winter season
Overcrowding
MODE OF TRANSMISSION
Droplet infection
Man to man transmission
Bird to man transmission
(H5N1,H5N2,H7N1,H7N7)
(H5N1-Fatal)
15. PATHOGENESIS
Acute inflammatory reaction
With incubation period of 1-3 days
Resulting in necrosis and desquamation of epithelial cells
favours secondary bacterial infection –Pneumonia
rare complications: encephalitis, polyneuritis.
Rarely involves heart ,nerves ,muscles.
16. CLINICAL SYMPTOMS:
• Fever(101-104 degree celcius),
• Chills, Severe headache, myalgia
• Loss of appetite, sore throat, dry cough
• Nasal discharge, conjunctival
congestion, sleep disturbance
17.
18. TREATMENT AND
CHEMOPROPHYLAXIS
Absolute bed rest
Analgesics and antipyretics (symptomatic relief)
Antiviral drug –Amanatidine and Rimantidine
Amanatidine :Treatment- 100 mg BD, oral, for 3 to 5 days
Chemoprophylaxis-4 to 8 mg /kg/day(Close
contacts)
Rimantidine :60% effective(Russia)
19. PREVENTION AND CONTROL
Elimination of reservoirs
Concurrent disinfection of respiratory secretions, linen, utensils,etc.
Cover mouth with handkerchief while sneezing and coughing
IMMUNIZATION:
< Killed vaccine(Inactivated Influenza vaccine)
2 types:
Saline(Aqueous) vaccine
2 doses given with 4 weeks interval(subcutaneously)
each dose(0.5 ml with 15 microgram of H antigen)
immunity lasts for 6 months(revaccination everyyear)
prepared by growing in allontoic cavity of chick embryo
20. Oil adjuvant vaccine dose (0.2ml)
It is an oil emulsified preparation
Advantage:
more effective than saline vaccine
immunity lasts longer for 1 year
Disadvantage:
cause sterile absess due to oil content
painful nodule
Some brand names of killed vaccines of influenza virus are
Afluria, Fluvirin, Afluria Quadrivalent, Fluarix Quadrivalent, FluLaval
Quadrivalent
21. Live attenuated vaccines:
given intranasally by nose drops
induce both local(IgA) and humoral (IgG)
immunity.
Eg : Flumist Quadrivalent
Newer vaccines:
recombinant flu vaccine
genetic recombination is done between human
and avian strain
Eg : Flublok, Flublok Quadrivalent.
22. Hurdles in the control
Mass immunization to be given at least 2 month before the
expected pandemic
Sudden antigenic change and mutability of the virus
Short incubation period
Rapid spread by droplet infection
Universal susceptibility
