Page updated 30 April 2007
Influenza
Introduction
There is much confusion between "bird flu", endemic and pandemic "flu".
Avian or Bird Influenza
Avian influenza curculates naturally in wild waterfowl such as ducks and geese, often without symptoms. Outbreaks in other species may be associated with high bird mortality. In January 2004, avian influenza associated with high mortality in poultry appeared in Vietnam. Subsequently, there have been very substantial outbreaks of this highly pathogenic avian influenza (HPAI) in domestic fowl in various countries in central, south and south east Asia. These outbreaks are caused by the H5N1 subtype of influenza A virus.
Rarely, avian influenza viruses are transmissible to humans in close contact with flocks causing sever respiratory illness with a high fatality rate. Several countries have reported human cases of H5N1 following close contact with infected birds. The avian virus does not readily transmit from human to human, but the potential for mutation of avian H5N1 into a form that spreads easily from person to person is a great concern for world health, as this could trigger a human pandemic.
Avian Flu - Links
United Kingdom
- Health Protection Agency Situation Update
- Health Protection Agency Avian Influenza Algorithm
- Avian Flu Information (BUPA Health Information Team)
International
- World Health Organisation Avian Influenza Infection Control Guidelines
- CDC Avian Influenza Information
Endemic Influenza
Influenza-like illnesses always increase in the winter months. For many years this has not been particularly noticeable in the United Kingdom. It is likely that most infections are asymptomatic. With other respiratory virus infections, influenza contributes to much minor disease in the winter leading to "winter pressures" in running our hospitals. This is not particularly because there are many patients who need admission but more because of the illness in carers and their families. Immunisation with a killed egg-derived vaccine including three of the most common strains seen in recent years is advisable to reduce the risk of illness in the elderly, infirm or in healthcare workers. This vaccine cannot protect against new strains.
Pandemic Influenza
The fear of pandemic influenza has been raised in parallel with the observations about "bird flu". If two strains from, say, a human and an animal infect one host at the same time, then a completely new mutant virus might be generated. This is how new strains emerge. Current vaccines will then not protect. Occasionally such a strain will be virulent, and successful in man. It is most likely that such strains will arise in southeast Asia where people live in very close proximity to their animals. There is surveillance to detect such new strains. When they have arisen in the past, it has taken several seasons for them to move accross the world. In other words, we should have advanced warning of such an event. So far, there is no evidence of a new strain in the offing! It is likely that a vaccine will not be immediately available when a new strain hits.
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