Influenza is an acute respiratory infection caused by influenza viruses types A, B, and C. Type A strains have caused all known pandemics. The virus is highly contagious and spreads rapidly through droplets. It commonly causes epidemics every 2-3 years for influenza A and 4-7 years for influenza B. While most cases are mild, influenza can lead to complications like pneumonia. Vaccination and antiviral drugs can help prevent and treat the disease. Good hygiene and avoiding crowded areas during outbreaks are also recommended.

1. INFLUENZA
L.CHANDANA
2K4-BATCH G.M.C

2.  An acute respiratory
tract infection.
 Caused by the. influenza
virus 3 types A. B. C.
 All known pandemics
caused by Type A strain.

3. EPIDEMIOLOGY
 Truly an international disease.
 For every 10 to 15 years pandemic
occur due to antigenic variation.
 1918 - Spanish influenza.
 1957 - Asian Influenza
 1968 - Hong Kong

4.  21 million people died worldwide
mostly due to secondary bacterial
pneumonia.
Epidemics occur between pandemics
at intervals.
2 - 3 years - Influenza A
4 - 7 years - Influenza B

5. UNIQUE FEATURES OF
INFLUENZA EPIDEMIC
 Large number of subclinical cases.
 High proportion of susceptible
population.
 Short duration of immunity.
• Suddeness
• speed and ease which they spread.
• short incubation period.

6. GRAPH

7. • All contribute to its rapid spread.
• At present 3 types are circulating in
the world A(H1,N1) A(H2,N2) B virus.
• WHO global surveillance identified
human infection with a new influenza virus
called A (H5,N1) in Hong Kong in mid 1957

8. AVAIN INFLUANZA
 It refers to the large group of different
influenza virus that primarily affect birds.
 Majority dont infect humans.
 However avaian H5,N1 is a strain with
pandemic potential,since it might
ultimately adapt into a strain which is
contagious among humans.

9. • In HongKong H5 N1 strain infected
human causing 18 cases including 6 deaths.
• In mid 2003 virus caused largest and
most severe out breaks in poultry on record.
• Since there over 100 cases have been
laboratory conformed in 4 Asian countries
named, Indonesia, Thailand, Cambodia,
Vietnam more than half people died.

10. Avian Influenza Incidence Tracking Map,
February 27th, 2006: 45 Countries Have Bird Flu.

11. 2005 TRACKING MAP

13. • Most cases are previously healthy children
and young adults.
• The virus is spreading rapidly reaching all
continents less than 3 months due to the
speed of international air travel today.

14. Death rates are determined by four
factors :
1. The number of people who become
infected.
2. The virulence of virus.
3. The underlying characteristics and
vulnerability of effected population.
4. Effectiveness of preventive measures.

15. EPIDEMIOLOGICAL DETERMINANTS
AGENT FACTORS
AGENT:
Family Orthomyxoviridae
There are 3 types :
Type A
Type B
Type C
•Antigenically distinct
•No cross immunity.

16. Current
classification
Old designation 1971classification Reference strains
H1 N1
H2 N2
H3 N3
A swine
A0
A1
A2
A2(Hong kong
Hsw N1
H0 N1
H1 N1
H2 N2
H3 N2
A/Swine/Wisconsin/15/30
A/PR/8/34
A/FM/1/47
A/Singa pore/1/57
A/Hong kong/1/68

17. • Both A&B virus have 2 distinct surface
antigens.
• Haemagglutinin (H)
• Neuraminidase (N).
H antigen initiates infection
N antigen release of virus from infected cell.

18. • Influenza A virus unique.
• Subjected to antigenic variation.
• A sudden complete or major change.
- Shift
Antigenic change is gradual over a
period of time - drift

19. DATE Antigenic sub type Remarks
1889-1900
1900-1910
1918-1933
1933-1946
1946-1957
1957-1968
1968
To the
present time
1977
To the
present time
H2 N8?
H3 N8
H1 N1(former Hsw
N1)
H1 N1(former H0w
N1)
H2 N2
H3 N2
H3 N2
H1 N1
Pandemic and epidemics
Extensive epidemics
‘Spanish flu'. the most severe pandemic
recorded:
Heavy mortality
Discovery of influenza viruses
(WS strain-1933):epidemics of ‘A0’straines
Epidemics of a1 stranges
E
Expensive pandemics of ‘Asian flu’formerly
Called a2(AIAN) strain, low mortality
Moderate pandemic of ‘Hong Kong flu’
Formerly called A2 timer (Hong Kong)
strains very low mortality.
Re-emergence of former A1 strains. first
appeared in Russia and china (red flu); mild
pandemic very low mortality

20. (B)RESERVOIR OF INFECTION:
• Mainly - Animals & Birds
• Some include H and N antigens
related to humans
• New strains by recombination influenza
virus between man animals birds.

21. (C) SOURCE OF INFECTION:
• Usually case are subclicinal case
Nasal secretions are infective.
• During epidemics,large number of
mild and Asympomatic occurs play
an important role in spread of infection.

22. (D) PERIOD OF INFECTIVITY:
• Nasopharynx
• 1 to 2 days before and
1-2 days after onset of symptoms.

23. HOST FACTORS
(A) Age and Sex:
All ages and both sexes
Highest mortality rate amount certain high
risks groups.
Example: Old people children under 18
months diabetes, or CHD.
(B) Human Mobility :
Important factors in spread of
infection.

24. (C) Immunity :
Subtype specific
Antibodies against HA AND NA
Antibodies appear about 7 days
after the attack and reach maximum level in
about 2 weeks after 8 to 12 months,level
drops to pre infection level.

25. ENVIRONMENT FACTORS
(A) Season –
In winter Northern Hemisphere.
Winter or Rainy Seasons in Southern
Hemisphere.
(B) Over Crowding :
Enhances transmission
E.g Schools,institutions,ships etc...

26. MODE OF TRANSMISSION :
Persons to persons by droplet infection or
nuclei created by sneezing, coughing,
talking.
The portal of entry of virus is respiratory
tract.
INCUBATION PERIOD :
18 to 72 hours

27.  PATHOGENESIS :
 Inflammation and necrosis of superficial
epithelium followed by secondary bacterial
invasion.
 No viraemia.

28. Clinical Features :
Fever,chills,aches,and pains coughing
and generalized weekness
fever lasts1 to 5 days.
Complications :
Pneumonia
Guillain Barre syndrome
Reye Syndrome
Fatty liver.

29. LABORATORY DIAGNOSIS
(A) Virus isolation :
Nasopharyngeal secretions.
Use secondary baboon kidney cells or
mardin darby canine kidneys (MDCK)
cells.
(i) Nonspecific CPE certain days
(ii) Haemadsorption before CPE.

30. (iii) Haemagglutination
(iv) Specific identification
by direct fluorescent antibody technique.

31. (B) Paired sera :
Essential to examine paired acute
convalscent sera to demonstrate a 4 fold or
greater increase.
In india,facilities for isolation of influenza
available at

32. A) Govt. of India. influenza virus centre,
Pasteur institute Coonoor, South India
(B) Haffkine institute, Mumbai
(C) School of tropical Medicine (Kolkotha)
(D) AIIMS (New Delhi)
(E) Vallabhai Patel Chest institute (Delhi)
(F) Armed Forces Medical College (Poona)

33. Prevention :
 Sensible precautions
 Good ventilation of public
buildings.
 Avoidance of crowded places
during epidemics.
 Encouraging suffers to cover their
faces.
 7 stays at home at the sign of
influenza.

34. A number of field trials have shown vaccines
are highly effective (10 - 90) administered at
least 2 weeks, before onset of epidemic.
Influenza vaccines recommended only in
selected population.
e.g. : In industry to reduce absenteeism in
public servants.

35. HIV infected, can be safely vaccinated.
vaccination less effective when CD4 count
< 100 / mcl.
Hygienic practices during handling of
poultry products including:
hand washing,
prevention of cross contamination and
thorough cooking to > 70 ' c of poultry
products.

36. Influenza Vaccines :
 Killed vaccines –
 Most vaccination programmes use.
 Grown in allantoic cavity of chick embryos
 Purified and killed by formalin or beta
propiolactone
 One dose of vaccine contains 15 micro
grams of HA
 Administrated Subcutaneously

37. • 0.5ml - Adult and children over 3 years
• 0.25 ml - 6-36 months of age
• Unprimed individuals - 2 doses
• Vaccine separated by 3-4 weeks
• Immunity lasts only 3-6 months
• Revaccination on a annual basis
recommended.

40. Disadvantages :
Fever, local inflammation rarely GB syndrome
signs of hypersensitivity.
LIVE ATTENDED VACCINES
Based on temperature sensitive mutants
used in USSR
Administrated as "nose drops"
Stimulate local and systemic immunity.
Frequent antigenic mutations cause
difficulty in production of effective
vaccines.

41. (c) Newer vaccines :
(i) SPLIT VIRUS VACCINES :
• Subvirion vaccine.
• Highly purified vaccine.
• Few side effects.
• Several injections due to its lower
antigenicity.
• Recommended for children

42. (ii) Neuraminidase specific vaccine :
Sub unit vaccine, containing N antigen
(iii) Recombinant vaccine :
ANTIVIRAL DRUGS :
Amantadine or Rimantidine in prophylasis
and therapy of influenza a virus infections.
Shortens duration of symptoms.
A dose of Amantadine or Rimantidine
100 mg twice a day for 3-5 days.

43. These drugs also modify severity
of influenza, if started within 24-48 hours of
onset of illness.
These drugs are not used as a
public health measure for wide spread
control of influenza.

44. THANK YOU