Flu, medically called “influenza” is a viral disease of the respiratory tract. There are various influenza viruses that cause flus.
The flu 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 sub-typing 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 the 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.
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 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 once a day 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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