The flu is
a respiratory illness caused by the influenza virus. The flu is not the same as
a cold,
although they share many of the same symptoms. The cold is caused by a
different virus, and it tends to have milder symptoms than the flu. Colds are
also less likely to cause serious complications.
When
the influenza virus gets into the body, it moves into the respiratory tract.
Once there, it binds to the surface of cells.
The virus then opens and releases its genetic information (RNA) into the cell's
nucleus. The nucleus is where the cell's genetic information (DNA and RNA) is
stored. The virus replicates, or copies itself, and takes over the functions of
the cell. The copies of the virus move to the cell membrane until the cell
finally dies and releases them out into the body, where they go on to infect
other cells.
The
respiratory tissues swell up and become inflamed (the inflammation usually
heals within a few weeks). As the virus moves through the respiratory tract and
into the bloodstream,
the first symptoms begin to emerge. The replication process continues for up to
several days, until the body's immune system begins
to fight the virus off.
Flu
symptoms can include any or all of the following:
·
Coughing
·
Sneezing
·
Fever
·
Body aches
·
Runny nose and/or congestion
·
Tiredness
These
symptoms, although uncomfortable, are generally not dangerous. But the flu also
weakens the immune system, leaving it vulnerable to more serious infections.
High-risk individuals in particular are susceptible to serious complications,
such as:
·
Bacterial pneumonia
·
Dehydration
·
Sinus problems and ear infections (primarily in children)
·
Worsening of preexisting conditions, such as asthma or diabetes
Source : http://health.howstuffworks.com
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