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Avian Influenza Infection

What is Avian Influenza?

Avian influenza, or 'bird flu', is a contagious disease caused by influenza viruses that normally infect only birds and less commonly, pigs. All bird species can be infected but, domestic poultry flocks are especially vulnerable. Various strains of influenza cause the infection and they are divided into low and high pathogenicity strains, based on the severity of infection in birds, not humans

Rarely humans become infected by ones of these avian influenza viruses. There are many different strains of influenza virus, but the ones that have caused most problems in humans are called H5N1 and H7N9.

Avian influenza infection in birds has a worldwide distribution. Human avian influenza virus infection may thus also occur worldwide with the greatest risk being where close contact between humans and potentially infected birds occur.  Egypt, Indonesia and Vietnam have reported the largest number of cases.

How are Humans Infected?

Birds shed influenza virus in their droppings, saliva and nasal secretions, spreading it onto their feathers.

Humans are usually infected through close contact with live infected birds or surfaces contaminated with their secretions (for example by visiting enclosures or wet markets where birds have been recently kept).

Very rarely infection has passed from an infected human to another through exposure to infectious body secretions.

The Illness in Humans

It usually only takes 3 - 5 days for symptoms to develop after exposure.

The severity of illness appears to vary. early symptoms are likely to be similar to normal influenza such as fever and cough

  • If you develop a fever, cough or breathlessness severe enough to need medical attention or become severely unwell, you should contact your General Practitioner if in the seven days before illness you:. 
    • Visited a country with an avian flu outbreak and had contact with live poultry or pigs or places that house them OR
    • Had close contact with someone known to have avian influenza.


Antiviral drugs, oseltamivir (Tamiflu) and zanamivir (Relenza) can be used for  treatment.

At present no vaccine is available against avian influenza in humans but in the event of a large outbreak a vaccine could be manufactured within months.


  • An advice sheet recommending ways of reducing the risk from avian influenza has been prepared for travellers to areas reporting human cases of avian influenza.
  • In special circumstances, antiviral drugs may be considered for those perceived to be at high risk.
  • The European Centre for Disease Prevention and Control has advised that 'It is not recommended that travellers take Oseltamivir (Tamiflu) with them'.

Further information

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