InfluenzaInfluenza
facts Frequently
asked questions
More information Influenza
factsInfluenza or flu is an
acute respiratory disease caused by a virus. It is also one of the
most common diseases causing seasonal epidemics across the world
every year.
The Influenza virus
Influenza viruses causing
disease in humans are classified into two groups: Influenza A viruses are
further classified into subtypes by Haemagglutinin (HA) and Neuraminidase
(NA) proteins present on the surface of the virus particle. Symptoms Influenza infection is
characterized by fever, muscle aches and respiratory symptoms such
as cough, sore throat, sneezing and runny nose. Most people recover completely
within 1-2 weeks. However, Influenza may lead to severe complications
such as pneumonia in infants, the elderly and immuno-compromised
individuals. Diagnosis Respiratory symptoms
during the flu season are indicative of Influenza. A definitive
diagnosis requires laboratory confirmation. Virus variations Influenza viruses have
the ability to change their genetic make-up by changes in the surface
proteins by two different mechanisms.
Firstly, small changes, known as antigenic drift, occur frequently.
The population is no longer completely immune to the virus and seasonal
outbreaks of Influenza occur. These antigenic changes also require
the annual reformulation of Influenza vaccines.
Secondly, Influenza A viruses may undergo major genetic changes
known as antigenic shift. This results in a new influenza virus
to which the human population is completely susceptible; an influenza
pandemic may result.
Influenza vaccines Annual vaccination helps
to prevent Influenza infection. Back
to top Frequently
asked questions How does the
Influenza virus spread?
Influenza virus is found in the secretions of the respiratory tract.
It is passed from person to person when infected individuals cough
or sneeze. The Influenza virus enters through the nose and/or mouth.
Multiplication of the virus takes place in the respiratory tract.
Flu symptoms develop within 1-4 days after infection. For how long
is flu contagious?
An infected individual can spread the Influenza virus from the day
before they begin to feel ill until 3-7 days after the start of
flu symptoms. Children are able to transmit the virus for longer
than 7 days. Some people may be infected
with Influenza virus but have no symptoms. During this time, they
can still spread the virus to others. Who should be
vaccinated against Influenza? - Annual vaccination will reduce the chances of contracting flu.
- Only children older than 6 months may be vaccinated.
- Vaccination is strongly recommended for groups at high-risk
of Influenza-related complications e.g. people older than 65.
People in contact with these risk groups should also be vaccinated;
this reduces the chance of exposure to Influenza for these groups.
How do I know
if I have flu?
A sudden onset of fever, muscle aches and respiratory symptoms is
indicative of flu. In the Northern hemisphere the flu season is
November to April. Flu may however be contracted at any time of
the year. Doctors can carry out tests in the first few days of illness
to determine if you have flu. Why do I have
to be re-vaccinated annually?
The Influenza virus undergoes constant genetic changes. Each “flu
season” the circulating virus is slightly different and you
are no longer completely immune to it. The virus composition of
the vaccines is adjusted annually to include the most recent circulating
Influenza viruses. Back
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