by Dr Pandula Siribaddana

Created on: August 15, 2009   Last Updated: August 22, 2009

Influenza is mostly a respiratory related illness which is acute in nature caused by a virus family known as 'Orthomyxo viruses'.

Types of the Influenza virus:

There are three sub types that have been identified which is known as Type A, B and to a lesser extent C. These viruses can cause minor to severe illness in mainly temperate climates, usually in the winter season.

The different types of the virus is being designated and identified through the proteins that are present as internal antigens and external antigens.

Internal antigen: these are named as M1 and NP proteins and is the type specific antigen in identifying if the virus is either Type A,B or C.

External antigen: Identified as HA and NA, these will enable identifying sub types and various strains of the virus.

Spread and the site of infections:

These viruses spread via droplets and can remain dormant in an outside environment for nearly 24 hours. It usually enters through inhalation and attacks the lining epithelium of the airways in the lungs. The damage that caused to the lining of the airways can hider the expulsion of phlegm and the organisms within and lead to infections of the respiratory tract.

Symptoms and complications:

When the influenza viruses affect the body, several types of system related symptoms are noticeable depending on the nature of the illness:

Uncomplicated: These would be Fever, headache, myalgia ,tearing from the eyes, eye pain, dry cough, nasal discharge..etc.

Pulmonary complications: In these instances, specially children can develop croup which is known as acute laryngotrachebronchitis and will cause difficulty in breathing, stridor and a barking type cough. The influenza can then lead to an influenza pneumonia which will cause difficulty in breathing for the patient. The inhibition of the protective cilliary mechanism would allow fluid and other organisms to get collected in the lungs and cause a secondary bacterial infection as well.

Non pulmonary complications: Although these are rare, the influenza infection can lead to several severe, life threatening complications such as encephalopathy, Reys syndrome which affects the liver and the brain, Guillain barre syndrome, cardiac complications and myositis in children.

Recovery:

The recovery is usually thorough the antibody response within the body. But, treatment options are available to reduce the disease burden and duration of the illness although its effectiveness is still under investigations.

Chemotherapy and vaccines:

Vaccines are available for the influenza viruses but its effectiveness varies with each strain due to the fact that viruses changes its identify in a process called antigenic drift and antigenic shift.

Chemotherapy options have come up in recent times with outbreaks of avian and swine flue epidemics in the world. These drugs, if taken early, can reduce the durations of the illness and reduce the complications that can happen as well.

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