The flu

1. SOMBIR SINGH
RESEARCH SCHOLAR
MD UNIVERSITY ROHTAK
SOMBIRKUMAR9195@GMAIL.COM
Influenza (The flu)Influenza (The flu)

2.  Influenza (the flu) is a contagious respiratory illnessInfluenza (the flu) is a contagious respiratory illness
caused by influenza viruses. It can cause mild tocaused by influenza viruses. It can cause mild to
severe illness, and at times can lead to deathsevere illness, and at times can lead to death..
 In virus classification influenza viruses are RNA
viruses/ Subfamily: Orthomyxoviridae.
 Influenza virus A
 Influenza virus B
 Influenza virus C
Influenza (The flu)Influenza (The flu)

3. the most virulent human pathogens among the
three influenza types.
 capable of infecting human as well as animals
(ducks, chickens, pigs, whales, horses and seals).
Wild aquatic birds are the natural hosts for a large
variety of influenza A.
 subtypes e.g., (H1N1), (H5N1),….
Influenza A virus

4. Influenza B virus
 it almost exclusively infects humans.
 less common than influenza A.
 are not divided into subtypes, but can be further
broken down into different strains.
I mutates at a rate 2–3 times lower than type A. This
reduced rate of antigenic change, combined with its
limited host range ensures that pandemics of influenza
B do not occur.

5. Influenza C virus
 infects humans as well as pig.
Uses to hemagluttinin esterase-fusion protein
enter or exit the cell
 less common than the other types and least
likely to mutate
usually only causes mild disease in children.

6. Virus Structure
The viral particles of all influenza Viruses are similar
in composition. These are made of a viral envelope
containing two main types of glycoproteins, wrapped
around a central core.
The central core contains the viral RNA genome and
other viral proteins that package and protect this RNA.

7. Virus Structure
Envelope
Helical nucleocapsid
Segmented, single stranded RNA of negative
polarity/must be copied into positive-sense
molecules in order to direct the production of
proteins.

8. Virus Structure

9. Hemagglutinin and Neuraminidase
There are 16 H and 9 N subtypes known, but only H 1,
2 and 3, and N 1 and 2 are commonly found in humans.
Hemagglutinin (HA) is a lectin that mediates binding
of the virus to target cells and entry of the viral genome
into the target cell.
Neuraminidase (NA) is involved in the release of
progeny virus from infected cells, by cleaving sugars
that bind the mature viral particles.
These proteins are targets for antiviral drugs.

10. Antigenic Variation
Influenza viruses tend to undergo changes from
time to time. There are two types of changes: (1)
antigenic shift, (2) antigenic drift. These changes
in the antigenic characteristics of influenza
viruses determine the extent and severity of
influenza epidemics

11. Antigenic Shift
• This term denotes MAJOR changes in hemagglutinin and
neuraminidase resulting from reassortment of gene
segments involving two different influenza viruses.
• When this occurs, worldwide epidemics may be the
consequence since the entire population is susceptible to
the virus.

13. Antigenic Drift
• This term denotes MINOR changes in hemagglutinin and
neuraminidase of influenza virus.
• This results from mutation in the RNA segments coding
for either the HA or NA
• This involves no change in serotype; there is merely an
alteration in amino acid sequence of HA or NA leading to
change in antigenicity.

14. Mode of Transmission In Human
• The virus is spread
from person- to-
person through
respiratory secretions
either as droplets
(close contact) or as
airborne infection by
droplet nuclei
suspended in the air.
• Incubation period 1-3
days

15. Clinical Manifestations
• Influenza is an acute
respiratory illness
characterized by
fever, headache,
myalgia, coryza, sore
throat and cough.
Cough is frequently
severe and
protracted.
• Duration of illness is
usually 2-7 days.

16. Infection Control

17. Vaccination
www.fightflu.com
1) Trivalent inactivated influenza vaccine: killed virus
injected into muscles
2) Live attenuated influenza vaccine: weakened virus
sprayed into nose
trivalent:
three strains predicted to dominate the coming
season
based on previous season

18. Antiviral Drugs
• Amantadine, rimantadine. Effective for prevention and
treatment of flu A only.
• Zanamivir, oseltamivir are approved for treatment of
uncomplicated flu A & B; oseltamivir also approved for
prophylaxis.
• Prophylaxis must be continued throughout the epidemic;
treatment must begin within 24 hrs of onset of illness.