2. • Contents 1. History 2. About the disease and types 3. Epidemiological trends
4. Prevention and Control. 5. Pandemic Influenza(h1n1) 2009 6. Special-
avian Influenza(outbreaks). 7. Newer vaccines and strains.
3. • History of influenza • 412 BC -
first mentioned by Hippocrates •
1580 - first pandemic described •
1580-1900 - 28 pandemics 3
Discovery of Influenza Virus •
First isolated from a pig in 1931
(swine flu) • Isolated from human
in 1933
4. • WHAT IS INFLUENZA? (ALSO KNOWN AS THE
FLU) • The flu is a contagious respiratory illness • It is
caused by influenza viruses • It can cause mild to severe
illness and at times can lead to death • It can be
prevented by getting the flu vaccination each year
Influenza: A Viral infection • Acute respiratory infection
caused by Influenza virus – Three types A, B and C. •
Currently viruses circulating in human population –
Influenza A (H3N2), A (H1N1) and B Strains. • All
known pandemics (global outbreaks) were caused by
Influenza A. • Animal influenza viruses may affect
humans in special circumstances – Bird Flu: A (H5N1).
5. • Naming influenza viruses A/Hong
Kong/156/97 (H5N1) Strain ID Type
Hemagglutinin Neuraminidase Origin
Year isolated 16 9 7 Influenza types Type
A Potentially severe illness Epidemics and
pandemics Rapidly changing Type B
Usually less severe illness Epidemics More
uniform Type C Usually mild or
asymptomatic illness Minimal public
health impact
6. Classification of Influenza virus • Classified on the basis of
hemagglutinin (HA) and neuraminidase (NA). • 16 subtypes of HA
and 9 subtypes of NA are known to exist in animals (HA 1-16, NA
1-9). • 3 subtypes of HA (1-3) and 2 subtypes of NA (1- 2) are
human influenza viruses. HA 5, 7, 9 and NA 7 can also infect
humans
