Influenza is a
highly contagious acute respiratory
disease caused by an RNA virus of the
orthomyxoviridae family. The name
influenza comes from the old medical
belief in unfavourable astrological
influences as the cause of the disease.
Influenza is a major cause of illness and
causes suffering in all age groups.
Epidemics of
influenza typically occur during the
winter months in temperate regions. In
annual influenza epidemics, according to
the World Health Organization, 5-15
percent of the population is affected with
upper respiratory tract infections. Every
year there are 3-5 million cases of severe
illness and between 250,000 and 500,000
deaths around the world due to influenza.
In the Northern Hemisphere, 100 million
people are infected with the influenza
virus each year and most of these patients
are debilitated in some way.
Influenza has been
responsible for an average of
approximately 36,000 deaths/year in the
United States during 1990 - 1999. In the
UK about 6,000 excess deaths occurred at
the time of influenza outbreaks during the
years 1987 - 1995. The attack rate for
influenza is highest among children aged
5-9 years, reaching 30% of this segment of
the population. Although the illness
burden in children is very high, the
mortality due to influenza generally
affects adults of 65 years or older.
Every 20 years or
so, there is a major change in an
influenza virus strain. When this major
change occurs a worldwide epidemic, called
a pandemic, almost inevitably follows
because influenza spreads very quickly,
especially with modern transportation
methods. Pandemic influenza
can produce an enormous increase in the
annual death toll; the 1918 pandemic may
have caused in excess of 40 million deaths
worldwide.
The following
persons are increased risk for
complications from influenza:
persons aged >65
years;
adults and
children who have chronic disorders of
the pulmonary or cardiovascular
systems, including asthma;
adults and
children who have required regular
medical follow-up or hospitalization
during the preceding year because of
chronic metabolic diseases (including
diabetes mellitus), renal dysfunction,
hemoglobinopathies, or
immunosuppression (including
immunosuppression caused by
medications or by human
immunodeficiency virus [HIV]);
children and
adolescents (aged 6 months – 18 years)
who are receiving long-term aspirin
therapy and, therefore, might be at
risk for experiencing Reye syndrome
after influenza infection;
women who will be
pregnant during the influenza season;
and
children aged 0 –
23 months.
ABOUT VACCINATION:
Currently licensed
inactivated influenza virus vaccines have
an excellent safety profile and are highly
effective in preventing acute illness and
serious complications. In addition to
providing substantial health benefits,
vaccination is also associated with
significant economic benefits, not only
among the elderly but also among healthy
working adults and even children. Hundreds
of millions of doses of theses
vaccinations are used each year.
Although
antiviral
drugs
can
be
used
as
a
prophylaxis
against
influenza,
vaccination
is
the
first
line
of
defense
in
the
prevention
of
influenza.
However,
if
vaccination
is
not
performed
during
an
epidemic,
or
if
vaccinated
subjects
remain
unprotected
during
an
influenza
outbreak,
for
instance
because
of
a
mismatch
between
a
circulating
influenza
strain
and
the
strains
in
the
vaccine,
the
use
of
antiviral
drugs
can
be
considered.
Also
for
patients
with
a
known
hypersensitivity
to
influenza
vaccine
the
use
of
antiviral
drug
is
indicated.
If
the
new
generation
of
antiviral
drugs
are
administered
within
24
to
48
hours
after
the
onset
of
symptoms
they
can
reduce
the
duration
of
uncomplicated
influenza
A
and
B
illness
by
approximately
1
day.
WHEN
IS THE BEST
TIME TO GET
THE FLU
VACCINE?
The
optimal time
to get
vaccinated
is March
through to
May.
