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Thursday, February 23, 2006

Health news - Avian flu (bird flu)

20 February 2006 - written by BUPA's Health Information Team

Avian flu (bird flu) has been found in poultry flocks and/or wild birds in a number of Asian countries. It has also been found more recently in birds in a growing number of countries across the Middle East, Europe and also in Nigeria. In some Asian countries, along with Iraq and Turkey, a small number of people have caught the bird flu virus from infected poultry.

Scientists fear that the bird flu virus could merge with a human flu virus. This might result in a new, flu virus that could be passed rapidly from person to person triggering the next human flu pandemic with potentially devastating results.

To keep the outbreak of bird flu virus under control, many of the affected countries are culling their poultry stocks to prevent further spread of the virus.

What is bird flu?

'Avian' refers to birds and 'flu' is the common name for influenza. Avian flu is influenza that normally infects birds, including wild birds such as ducks and migratory birds and also domestic birds such as chickens. Avian flu is caused by influenza virus type A. There are 16 H subtypes of influenza A. The subtypes H5 and H7 are known to cause the highly pathogenic form of the disease. These bird viruses are referred to as being "highly pathogenic" as they produce a severe disease in birds and are rapidly fatal, leading to bird flu epidemics. The H5N1 subtype is the virus causing concern across the world at present.

Why are we so concerned about bird flu?

Flu viruses are known to change constantly. The bird flu virus can occasionally jump between species and infect people who have been in close contact with infected birds.1

In the current outbreaks involving the H5N1 virus, some of the people who have been in close contact with birds have become very ill or have died. To date, 170 people have been infected and 92 of these people have died.2

How is bird flu virus passed from birds to people?

When a bird is infected with bird flu, it sheds the flu virus in its faeces, saliva and mucus. Other birds become infected by eating or inhaling the virus10. The virus can infect people who are in close contact with infected birds.1

The UK Food Standards Agency and European Food Safety Agency have advised that there is no evidence that people can catch bird flu from eating cooked chickens. In areas free from the disease, poultry and poultry products (including eggs), can be prepared and eaten as usual following everyday hygiene advice.3

Can bird flu be passed from person to person?

The ability of bird flu viruses to infect humans throws up this worrying possibility.

A bird flu virus could merge with a human flu virus to create a new virus. This new virus could then be passed between humans. There would be very little immunity among humans against this virus. It could therefore be passed rapidly between people.

What is a flu pandemic?

The new virus could spread rapidly around the world with the potential for widespread loss of life. Pandemics occur sporadically - there were three in the last decade. One example is the Spanish flu pandemic of 1918-1919 which caused an estimated 20-40 million deaths worldwide. The symptoms of pandemic flu are similar to ordinary flu but are usually more severe.4

How can a pandemic human flu virus develop?

There are two ways in which a bird flu virus could merge with a human flu virus, creating a new virus that can be easily passed between humans:

Reassortment - when an animal or human becomes infected with a human and animal flu virus at the same time resulting in an exchange of genetic material and producing a new virus capable of causing a pandemic in humans.5

Adaptive Mutation - this is a more gradual process where the virus becomes capable of binding to human cells acquiring the ability to pass easily from person to person.6

Has bird flu been passed between people?

So far there's no firm evidence that it can do so in a sustained and efficient way. However, there are instances where this has happened, to a very limited degree, between close family members, but the virus has not spread beyond that. The World Health Organisation says this is not a cause for alarm.6

Does this mean the human and bird flu viruses have merged?

No. Scientists have not discovered an influenza type a (H5N1) virus that contains both human and bird virus genes. This means that the bird flu virus has not merged with the human flu virus.6

These isolated cases of person-to-person transmission may have been caused by the basic bird virus being passed on due to very close contact.

What are the symptoms of human flu?

Human flu symptoms are:

  • fever
  • cough
  • headache
  • severe weakness and fatigue
  • sore throat
  • aching muscles and joints
  • runny nose

Cases of bird flu are more likely to cause more severe symptoms in many people and in some people, breathing problems and pneumonia. In human cases, to date, around half have been fatal.

Are there any treatments available for bird flu?

Antiviral medication used to treat human flu viruses may be effective at treating bird flu. The antiviral drugs called oseltamivir (Tamiflu) and zanamivir (Relenza) can reduce the severity and duration of ordinary flu (if given within 48 hours of symptoms starting). Experts expect the drugs to be effective against the H5N1 virus. However, in a pandemic, they cannot be sure until a new virus emerges. It is possible, though that the virus could develop resistance to the drugs6. The UK government is stockpiling supplies of oseltamivir and is constantly reviewing its strategy. The WHO advises that for now, oseltamivir remains the drug of first choice.6

Is there a vaccine to stop people getting bird flu?

There is currently no vaccine to prevent bird flu in humans. Although a vaccine against the H5N1 strain of the virus is under development, until a pandemic starts and a new pandemic virus emerges, it will not be possible to produce an effective vaccine.6

What is the current advice for travellers to countries affected by bird flu?

As of 20 February 2006, countries affected by bird flu in poultry and/or wild birds include: Austria, Azerbaijan, Bulgaria, Cambodia, China, Croatia, Egypt, France, Germany, Greece, Hong Kong, Indonesia, Iraq, Iran, Italy, Japan, Kazakhstan, Korea (North and South), Laos, Malaysia, Mongolia, Nigeria, Romania, Russia, Slovenia, Thailand, Turkey, Ukraine and Vietnam.8

There are no current restrictions on travel. The advice for travellers to countries affected by bird flu is to avoid places where live poultry are raised or kept, such as poultry farms and bird markets, and to avoid contact with sick or dead poultry. Travellers should also avoid any under-cooked poultry or eggs. Travellers should not attempt to bring any live birds or poultry back into the UK.9

What can be done to contain the spread of bird flu?

In the countries that have been affected by bird flu, governments, along with the World Health Organisation, are attempting to contain the virus by culling affected poultry stocks. However, the World Health Organisation says it is increasingly doubtful that the virus can be eliminated in birds in the near future. Countries such as the UK have drawn up detailed plans to deal with and contain a possible pandemic.11

Further information


  1. Avian Influenza, February 20 2006
  2. Cumulative Number of Confirmed Human Cases of Avian Influenza A/(H5N1) Reported to WHO, February 20 2006
  3. Bird Flu Update, Food Standards Agency, January 5 2006
  4. Pandemic Flu: important information for you and your family, Department of Health, October 19 2005
  5. Explaining Pandemic Flu, Department of Health, October 19 2005
  6. Avian Influenza, Frequently Asked Questions, World Health Organisation, December 5 2005
  7. Avian Influenza - situation in Turkey - update 4: sequencing of human virus, WHO, January 12 2006
  8. Update on Avian Influenza in animals, OIE - World Organisation for Animal Health, 20 February 2006
  9. Foreign & Commonwealth Office information and WHO recommendations relating to travellers coming from and going to countries experiencing outbreaks of highly pathogenic H5N1 avian influenza
  10. Bird flu and pandemic influenza: what are the risks? Department of Health, January 16 2006