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Flu is an acute respiratory illness caused by the A and B flu viruses that appears during the winter months. An outbreak of flu can sometimes become a pandemic. It is an illness that may present a wide range of clinical symptoms; from asymptomatic infections to respiratory conditions that may result in complications and end up affecting the entire body.


What is flu?

The flu virus multiplies in the respiratory epithelium and from there is spread through saliva. The incubation period ranges between one and four days. It is highly contagious for the first three or four days of the illness, although in some cases this may be longer.  

Most patients recover in one or two weeks without requiring medication.

Flu can cause complications needing specific attention in very young children, the elderly, those with serious conditions and people with various chronic illnesses.



The range of flu symptoms is very broad, but the main ones are:

  • sudden high fever
  • headache  
  • general tiredness
  • muscle pain  
  • respiratory symptoms such as a cough and sore throat


Who does flu affect?

Flu epidemics occur in seasonal outbreaks of varying intensity during the coldest months of the year as a result of the A and B virus antigens.

In closed institutions (nurseries, schools, care homes, barracks) most people may be affected. In addition to epidemics, flu pandemics can be caused by new subtypes of the type A flu virus.



Flu is diagnosed via respiratory tests (nasopharyngeal swab or aspirate) There are currently tests available that give a result in under an hour that are highly specific and sensitive.


Typical treatment

A family of antivirals called neuraminidase inhibitors are available and are very effective against the flu virus. However, these are only recommended for high risk patients.

Antibiotics are not advisable to treat flu except in cases where there is also a bacterial infection. These should always be taken according to medical prescription. For cases with no complications, treatment for flu consists of reducing symptoms with antipyretics and analgesics such as paracetamol.



The best way to prevent flu is through vaccination and good hygiene practices.

The immunity acquired following vaccination or suffering a bout of flu is long-lasting and specific to the subtype contracted (vaccinal). However the virus’ genetic variation does limit this period.

Vaccination is annual and is particularly recommended for people at high risk of suffering complications if they contract flu. 

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