Influenza

What is Influenza?

Influenza, also called the flu, is a contagious viral infection of the nose, throat and lungs caused by the influenza virus. Outbreaks of flu occur almost every year, usually in the colder months.

What is the cause?

The influenza virus causes more severe symptoms and complications than other respiratory viruses, such as the viruses that cause the common cold. It is caused by three types of viruses - Influenza A, B and C. Type A is usually responsible for the large outbreaks and is a constantly changing virus. New strains of Type A virus develop regularly and cause new epidemics every few years. Type B causes smaller outbreaks, and type C usually causes mild illness.

Influenza can affect individuals of all ages and is generally more frequent during the colder months of the year. People with chronic medical problems, the elderly and with compromised immune systems are particularly at risk for more severe flu symptoms or complications. The infection is transmitted from one person to another through respiratory secretions during coughing and sneezing. The droplets released into the air by coughing or sneezing can carry the virus. It can also be spread by the hands of infected individuals if they touch their nose or mouth.

What are the symptoms?

Influenza tends to start suddenly. The usual initial symptoms include high fever, chills, sweating, muscle aches and headache. Subsequent symptoms may include a runny nose, cough, sore throat and eyes sensitive to light. These acute symptoms usually last 3 to 5 days and often start improving gradually after the first 48 hours.

Infection with the flu virus may lead to other superadded infections. Ear, sinus, and bronchial infections are examples of such infections. Pneumonia can also occur as a result of the flu. It can be caused by the influenza virus itself or by bacteria causing a secondary infection. The symptoms include:

• High grade fever (38(C to 40(C) with chills
  
• headache
  
• muscle aches and stiffness
  
• nasal discharge
  
• cough
  
• shortness of breath
  
• chills
  
• fatigue
  
• sweating
  
• loss of appetite
  
• stuffy, congested nose
  
• sore throat

How is the diagnosis made?

Diagnosis of Influenza can usually be diagnosed from the symptoms. The evaluation of an individual with symptoms of influenza should include a thorough physical examination and in cases where pneumonia is suspected, a chest X-ray. Also a complete blood count, blood cultures and sputum cultures are done. If available, it may be diagnosed by antigen detection tests, which are done on nose and throat (nasopharyngeal) secretions by swabbing these areas with a swab and then sending a sample to the virology laboratory for testing. The results of these tests can be available rapidly, and can help decide if specific treatment is appropriate.

What is the treatment?

For mild illness in people who are not at high-risk, - the treatment of influenza is frequently just supportive and includes bed rest, analgesics (pain killers) for muscle aches and pains, and increased intake of fluids. If influenza is diagnosed within 48 hours of the onset of symptoms, especially in high-risk groups (immunosuppressed, elderly, chronic heart, lung or kidney conditions) antiviral medications are available, which may shorten the duration of symptoms. Treatment is usually not necessary for children, but if the illness is diagnosed early and the patient is at risk of progression to more severe disease, it can be started.

It is very important to drink a lot of liquids like water, juice, and other fluids. Having enough fluids also helps the mucus in the sinuses and lungs to stay thin and easy to clear from the body.

Over the counter fever-lowering medicines like paracetamol are recommended to lower fever. Some doctors feel that because fever is part of the immune system's reaction to infection, it is better to let fever run its course than to try to lower it. Letting the fever run its course, however, can be dangerous in children and the elderly. Also, most healthy adults feel much better if the fever is decreased by 1 or 2 degrees. If the nose or sinuses become congested, decongestants may help one feel better and may possibly help prevent ear or sinus infections. Cough suppressants may also be used for a cough. Antihistamines have a very drying effect and may cause the mucus in the nose and throat and lungs to become thick and dry. However, antihistamines can be helpful if a runny nose is making it hard to sleep.

Aspirin is contraindicated in children because of an unusual complication of flu known as the Reye’s syndrome, which usually occurs in children and adolescents and rarely occurs in adults. Reye’s syndrome is not well understood but it involves failure of the liver and brain swelling, which together can lead to coma and sometimes death. A link has been shown between the use of aspirin during influenza illness and the development of Reye’s syndrome.

There are anti-viral medicines that can make flu symptoms less severe. These include amantadine, rimantadine, zanamivir and oseltamivir, and are available as tablets or nasal sprays. They may also help the symptoms not last as long. They must be started within the first 48 hours of illness to be effective. The simplest, oldest method of avoiding spread of infection is frequent hand washing, preferably with an antibacterial soap.

What is the prognosis?

In most individuals who are otherwise healthy, influenza resolves fully within 7 to 10 days. Among individuals in high-risk groups (elderly, immunosuppressed, chronic heart, lung or kidney conditions) influenza may be quite severe and can lead to complications.