- What is “bird flu”?
- How is the disease spread?
- Where have there been outbreaks of the highly pathogenic disease?
- Can we stop it spreading throughout Europe?
- What would happen if there were an outbreak of avian influenza in the UK?
- Can I catch “bird flu”?
- Does avian influenza affect humans?
- Can people catch H5N1 avian influenza from other people?
- Why is there so much concern about the current outbreaks?
- What is a Pandemic?
- Can my doctor give me a vaccine against the H5N1 flu strain?
- What are Governments doing to control the H5N1 virus?
Q: What is “bird flu”?
A: Like humans and other animal species, birds are susceptible to influenza viruses. There are many different strains of Avian Influenza causing a range of symptoms in birds from mild sneezing to severe respiratory distress and death. The most contagious strains, which usually cause very high mortality in domestic poultry, are of the H5 and H7 type. The strain currently causing widespread disease in the poultry industry of SE Asia, and causing worldwide concern, is the H5N1 strain. This is classified as a highly pathogenic avian influenza (HPAI) strain.
Q: How is the disease spread?
A: Avian influenza can be spread in many ways. Wildfowl, particularly ducks and geese, are natural carriers of the viruses though they are relatively resistant to the disease and usually only develop mild symptoms. Infected birds pass the virus in nasal secretions and in their droppings. It may spread from farm to farm, for example, on people’s shoes, clothes or vehicle tyres.
Q: Where have there been outbreaks of the highly pathogenic disease?
A: Outbreaks of HPAI have been reported for well over 100 years in Europe, USA and SE Asia. The H5N1 strain was first isolated from a farmed goose in China in 1996. It has steadily spread and has become endemic in poultry in SE Asia over the last 12-18 months. Recently, there have been reports of disease in wildfowl and domestic poultry in SE Russia, Mongolia, Kazakhstan, Turkey, Croatia and Romania. The H5N1 strain of avian influenza has been confirmed in all these outbreaks.
Q: Can we stop it spreading throughout Europe?
A: Because migratory birds carry the virus, there is no way to stop it spreading from country-to-country. Many veterinary experts believe that it is only a matter of time before the disease spreads across Europe and will eventually cause outbreaks on UK poultry farms.
However, most poultry farms operate high levels of biosecurity to protect their birds, not just from avian influenza, but from other serious avian diseases. This includes various measures such as restricting visitors and vehicles from entering farms, using dedicated clothing and using disinfectant footbaths at the entrance to each poultry house. These measures are likely to be increased with this current scare.
Q: What would happen if there were an outbreak of avian influenza in the UK?
A: The Department for Environment, Food and Rural Affairs (Defra) has already published a contingency plan setting out the measures that would be taken in the event of a suspected case being notified.
The control measures would involve confirmation of the disease strain, culling of all infected birds and their contacts, imposing movement restrictions in an area around the infected premises, close monitoring of other farms in the area and recommendations for a heightened level of biosecurity/hygiene measures to be taken on poultry farms. Free-range poultry would be likely to be kept indoors.
They will also make available personal protective equipment (PPE) and antiviral drugs, if required, to veterinary surgeons, farm workers and contractors who are exposed to the virus while taking these disease control measures.
Q: Can I catch “bird flu”?
:A: You are extremely unlikely to catch bird flu unless you are in close contact with live birds infected with a highly pathogenic avian influenza virus.
Q: Does avian influenza affect humans?
A: Although outbreaks of avian influenza have been noted for over 100 years, it is only quite recently that severe respiratory disease caused by avian influenza viruses has been reported in humans. The strains implicated have been of the highly pathogenic H5 and H7 types.
The first report of human death from infection with the H5N1 virus was in Hong Kong in early 1997. Later that year in Hong Kong, a further 18 people were hospitalised and 6 of them died. Investigations suggested that they had been in close contact with live, infected poultry. This led to the slaughter of all poultry in Hong Kong. Since then the H5N1 virus has spread throughout SE Asia.
The virus is now reported to be endemic in poultry in that region. Around 120 human cases have been confirmed with over 60 deaths. Over 40 of those deaths have occurred in Vietnam. These cases have predominantly been shown to involve people in direct contact with infected, live birds.
An outbreak of H7N7 avian influenza occurred in the Netherlands, Belgium and Germany in early 2003. There were over 80 confirmed human cases, the vast majority of whom only suffered from mild conjunctivitis. There was one death attributed to infection with the H7N7 strain, in a Dutch veterinary surgeon that had visited an affected farm.
Q: Can people catch H5N1 avian influenza from other people?
A: To date, there is apparently some doubt over the ability of an H5N1 infection to spread from person to person. In three instances, it is possible that a very limited spread has occurred to those caring for close family members with serious respiratory illness and to a hospital worker. The disease did appear to be milder in those contacts and there is no evidence that the virus has adapted to spread easily in humans.
Q: Why is there so much concern about the current outbreaks?
A: Influenza viruses have some clever ways of outwitting the body’s immune defences. Firstly, they are not very good at copying their genetic material.
Errors in replication cause mutations that can lead to the formation slightly different strains. Because the virus is continually changing, production of an effective vaccine becomes a much more difficult process.
Secondly, they are able to “swap” genetic material with other influenza viruses. This can lead to the formation of a “new” type of influenza virus.
The big concern in the present situation is that the H5N1 avian strain will mutate or pick up part of a human influenza virus genetic material and form a new strain. A “new” highly pathogenic virus that could spread easily from person-to-person would constitute a real threat of a worldwide epidemic – a pandemic. It is possible that people throughout the world could have little or no immunity to this new strain and with the freedom to travel that we have these days, disease could be spread rapidly.
During the 1968/69 “Hong Kong flu” pandemic, the disease spread from Asia to UK in around 6 months.
Q:What is a Pandemic?
A: Influenza is a common respiratory illness that occurs all over the world and is responsible for considerable sickness and mortality each year. In the UK, influenza usually occurs during the winter months and up to 15% of the population may develop some symptoms, usually only mild, in any one year. Most years, around 30,000 – 120,000 cases are reported to doctors and up to 4,000 deaths are directly attributed to influenza.
From time to time the number of cases will be higher. In 1999/2000, 150,000 cases of illness were reported and, in 1989/90 – the last epidemic year - the figure was 325,000 cases with nearly 30,000 deaths.
To be classed as an epidemic, more than 400 cases must be reported per 100,000 of the population. For the UK, this equates to about 225,000 cases.
A pandemic is simply a worldwide epidemic.
Pandemics are caused by pathogenic strains of influenza viruses to which most people have no immunity. They spread very quickly worldwide and cause serious illness in very many people and can cause many millions of deaths. In the 20th century there were at least three major pandemics, 1918/19 (Spanish flu), 1957/58 (Asian flu) and 1968/69 (Hong Kong flu). The strains involved in these outbreaks were probably all derived from avian influenza viruses.
There have been no pandemics since 1969, but experts do believe that it is only a matter of time before another one occurs. The H5N1 virus is thought to represent the most likely candidate for many years to evolve into a “pandemic” strain.
Q: Can my doctor give me a vaccine against the H5N1 flu strain?
A: No. The currently available vaccine does not protect against the H5N1 virus. The vaccine available this year is designed to give protection against the most common pathogenic strains that are causing human disease, at this moment.
Because influenza viruses are constantly changing, several strains of the virus are circulating worldwide, and the predominant strains change from year-to-year. The World Health Organisation (WHO) constantly monitors the situation and publishes annual recommendations on the strains that should be included in influenza vaccines for the following winter. In the northern hemisphere, vaccines are manufactured from late spring and through the summer, so that stocks are available in the autumn to protect people from influenza.
However, many pharmaceutical companies are already working on vaccines against the H5N1 strain and, should the WHO recommend it, will be well prepared to include the strain in future vaccines.
Q: What are Governments doing to control the H5N1 virus?
A: Governments around the world are monitoring the spread of influenza and, in particular, the H5N1strain. When outbreaks in wild birds or poultry are discovered, measures are taken to control the spread, predominantly by culling the birds involved and any on surrounding farms.
Like other governments, the UK is also monitoring wild bird migrations and investigating any unusual patterns of deaths in wild birds, as a means of providing early warnings of the arrival of the disease.
Governments and NGOs, such as the World Health Organisation, are also monitoring and investigating cases of human disease.
The hope is that outbreaks of “bird flu” can be contained rapidly thus reducing the risk of the formation of a virus that could spread easily in humans.
In the EU, strong laws have been put in place to enable swift action in avian or human disease situations
