Dr. Md. Salequr Rahman
Dep. Of Community
• Acute Respiratory Tract infection caused by
influenza virus, A, B and C.
• Known pandemic caused by A.
• Sudden onset of
chills, malaise, fever, muscular pain and
• Truly an international disease. May occur in
pandemics every 10-15 years due to major
antigenic changes. In between
pandemics, epidemic may occur at intervals
of 2-3 years.
• At present 3 types of influenza viruses are
circulating in the world: A(H1N1), A(H1N2)
• Large group of different influenza viruses that
primarily affect birds. H5N1 virus is a strain of
pandemic potential. First infected human in
1997 in Hongkong.
• Agent: Type A, type B and type C.
• The influenza virus is unique among the viruses
because it is frequently subject to antigenic
variation. When there is a sudden complete or
major change, it is called a “shift”.
• When the antigenic change is gradual over a
period of time, it is called a “drift”.
• Reservoir of infection:
Animals and birdsswine, horses, dogs, cats, do
mestic poultry, wild birds
• Source of infection: Case
or subclinical case. Usually
• Period of infectivity: 1-2
days before and 1-2 days
after the onset of symptoms.
• Age and sex
• Environmental factorsseason, overcrowding
• Good ventilation at public
buildings, avoidance of crowded
places during epidemics, cover
the face with handkerchief, to
stay at home at first sign of
• Vaccination- effective if
administered two weeks before
• Vaccines recommended for certain
groups of people- in industry, for
public services, elderly, persons
with chronic diseases, HIV infected.
• Killed vaccine (immunity lasts for
3-6 months), annual revaccination
is necessary/ live attenuated