Questions and answers on avian influenza
About avian influenza (bird flu)
- Q: What is avian influenza?
- A: Avian (bird) influenza (flu) is a contagious disease caused by viruses that normally infect only birds. All birds are thought to be susceptible to infection with avian influenza, though some species are more resistant to infection than others. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide.
Rarely, avian influenza can infect mammals like pigs, tigers, leopards and cats. Avian influenza viruses can also rarely infect humans. Since humans do not have natural immunity against the virus, it can cause severe illnesses and death.
- Q: What is the difference between ‘avian influenza' and human influenza?
- A: Human influenza and avian influenza are both caused by influenza viruses but there are many different types of influenza viruses and some prefer to infect humans and others birds. Certain influenza viruses routinely infect humans causing seasonal outbreaks of influenza. Avian influenza viruses do not usually infect humans.
- Q: How many forms of avian influenza are there?
- A: Avian influenza infection causes a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is known as “highly pathogenic avian influenza”. This form is characterized by sudden onset, severe illness, and rapid death, with a mortality that can approach 100%.
Influenza viruses can be classified using a system of two letters (H and N) and two numbers e.g. H5N1. Sixteen H subtypes of influenza virus are known to infect birds. To date, all outbreaks of the highly pathogenic form have been caused by influenza A viruses of subtypes H5 and H7.
- Q: How is avian influenza transmitted?
- A: The avian influenza virus is shed in the saliva, nasal secretions and droppings of infected birds. Some species of birds will appear sick when infected but other species, particularly wild waterfowl and domestic ducks, may not show any symptoms of infection but will still excrete the virus. Once excreted, the virus can survive in the environment for some time, even weeks in certain temperatures and conditions.
- Q: What is H5N1 avian influenza?
- A: H5N1 is one particular form of avian influenza that is of major concern at the moment because, since December 2004, it has caused more than 100 human cases and killed millions of birds throughout the world. Occasionally other animals, like tigers and civet cats, have also been infected and died.
The relationship to human health
- Q: How can humans be infected with avian influenza?
- A: It is believed that most avian influenza infection in humans have been caused through close contact with infected poultry or their excretions.
There is currently no evidence of efficient or easy transmission of avian influenza from person to person but intimate physical contact with a person infected with avian influenza may be a risk. There have been a small number of events where limited human-to-human transmission of avian influenza may have occurred through very close contact.
- Q: Who is at risk of avian influenza?
- A: Any person who is exposed to live or dead chickens infected with the virus or their environment is at risk of getting avian influenza. This includes farmers, butchers, people who sell live birds or poultry, people who sell raw poultry meat in the market, people who prepare food from poultry products, children who play in areas where poultry is raised in free range and people who come into very close contact with those who are infected with avian influenza.
- Q: What are the symptoms of avian influenza in humans?
- A: The symptoms of avian influenza in humans range from flu like symptoms like cough, sore throat, high fever, muscle aches, to eye infections, pneumonia, severe respiratory distress and other severe and life threatening complications.
The symptoms of illness probably develop 3-7 days after contracting infection with the virus. In some patients diarrhea or neurological symptoms may be seen.
- Q: Should people cook and eat chickens which have died in their backyard farms?
- A: People should NEVER eat poultry meat or other products like eggs from poultry which have died from an illness or are sick. The concerned authorities should immediately be informed about the unusual deaths of the poultry. The carcasses of these poultry should be appropriately disposed, in order to make sure that they do not cause further infection.
- Q: Should people continue to eat poultry and their products during the avian influenza outbreak?
- A: There is no scientific evidence that bird flu is food borne. Proper cooking will destroy the avian influenza virus. Provided it is properly cooked and prepared in a hygienic way, poultry products are safe to eat.
The consumption of raw poultry or eggs should be avoided, because apart from the uncertain risk of avian influenza, it could also lead to other food borne infections.
Food hygiene, which includes thorough and frequent washing of hands as well as prevention of cross contamination throughout the poultry handling and cooking process, can reduce the risk of infection.
- Q: Is there any medicine or vaccine that can prevent humans from avian influenza?
- A: Three antiviral drug are licensed in some countries for the prevention of influenza:
Oseltamivir, marketed as Tamiflu®; Amantadine; Rimantadine
Analysis of the viruses isolated from fatal human cases in Vietnam indicates that current H5N1 viruses are resistant to amantadine and rimantidine. The current H5N1 viruses do however appear to be sensitive to oseltamivir.
A vaccine for humans against avian influenza H5N1 is being developed but is still in the experimental stage.