Influenza
or "The Flu"Influenza is a viral disease of the respiratory
tract. It is very contagious and is particularly dangerous for people above 65
years of age and unimmunized infants. It leads to viral and bacterial pneumonia
and affects people with a weakened immune system such as patients with cardiac
problems, kidney problems, diabetes and other metabolic diseases, anemia or states
of immune depression (including cancer and AIDS). There are three major types
of influenza
viruses, type A, B and C. Type A and its subtypes is mostly responsible
for the big epidemics. The subtyping is done according to the surface glycoproteins
of the virus. The two types are called hemagglutinine (H) and neuraminidase (N).
One of the latest subtypes of influenza A would then be termed "influenza
type A/Sidney 97(H3N2)". This means it was first detected in Sidney in 1997
and was of he type H3N2.
As
the human influenza virus can be transmitted between species such as swine, humans,
wild and domestic fowl, there are constant minor genetic variations where bits
of genetic material is incorporated or modified in the influenza genome. This
leads to the world wide epidemics as people are suddenly unprotected against the
new genetic strains of influenza. For instance, the pandemic of 1968 was caused
by a human influenza virus containing segments of an avian influenza virus, which
at that time was unknown to the immune system of humans. This is the rationale
behind a world wide flu watch by the Center of Disease Control. When a genetic
shift has been detected, massive vaccination programs are launched to protect
the public from the spread of these new forms of influenza. Many people have now
taken the yearly flu injection. This is one way to always stay on top of the genetic
changes or the influenza virus as much as possible. It is similar to an anti-virus
computer program. You are a lot safer with such a program, but you can never be
100% covered as it will take some time to develop a remedy for the latest version. Symptoms: In
the beginning there is a high fever, headaches, painful muscles (myalgia), a sore
throat and a cough. The cough can be severe to the point where vomiting can occur.
Other symptoms will subside within 2 to 7 days, but the cough usually persists,
often 2 to 3 months. The severity of influenza can vary from that of a cold, to
croup, to bronchiolitis or viral pneumonia. It may be indistinguishable from other
viral respiratory illnesses. If ASA is used in children with type A or B influenza,
there is a 35-fold higher risk of these children developing Reye's syndrome, which
has a high death rate.
| Reye's
syndrome : | | This is
a combination of a severe encephalopathy (brain damage) and liver disease (fatty
infiltration), which has an average death rate of 20%! The key to remember from
this is that children below the age of 18 should avoid ASA and only use acetaminophen
(Tylenol) to control a fever or headache in order to prevent this. |
Treatment: Treatment
for influenza on an individual level is symptomatic therapy like for a cold. Fluids,
bed rest, inhalation and antibiotic therapy for the few cases of bacterial superinfection,
if it comes to bacterial superinfections of sinusitis, otitis media, tracheitis,
or pneumonia. On a community level it is important to do something about
prevention of transmission of the disease. This starts with staying at home on
the first 3 to 5 days where the fever is high and the virus sheds from the infected
lining of the airways (in children this infectious stage may last up to 7 days).
In this stage droplets of the patient contain lots of virus, which is easily transmitted
in crowded conditions such as school buses, factories, schools, government offices,
churches and other forms of gatherings. Vaccinations on a regular basis every
fall in the temperate zones of the planet, or before the rainy season in tropical
zones on a yearly basis is the solution to the changing genetic influenza pattern.
The vaccine manufacturers automatically change the composition of the vaccine
according to the latest epidemic influenza strains. Using the vaccine among the
high risk population of older than 65 year-olds has reduced the mortality rate
by 80% and the complication rate of pneumonia and heart failure by 50 to 60%.
If this is combined with immunization against pneumococcal pneumonia, the success
rate is even higher! (Ref. 1, p. 270). Patients who are allergic to egg protein
cannot take the flu vaccine (this is a minority of the population).
There
are two antiviral drugs that are effective against influenza A, amantadine and
rimantadine. They will interfere with the penetration and uncoating of the virus,
which blocks the infectious process. It has to be taken within 48 hours of the
start of influenza to be effective. It is useful to protect the unimmunized patient
and it is useful in preventing disease in family contacts. The dosage is 100 mg
twice per day for ages 15 to 65. In older patients amantadine is reduced to 100
mg as it is eliminated via the kidney and kidney function deteriorates with age.
Rimantadine does not have this limitation as it is eliminated via the liver metabolism.
Side effects with amantadine are considerable. They consist of CNS side effects
with lightheadedness, dizziness, ataxic gait, depression, lack of appetite and
slurred speech. Some of these side effects wear off with continued therapy. However,
long term use beyond 1 or 2 weeks is not recommended as resistance of the virus
strain against the influenza A virus develops fast. |
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