It has been known for some time that a wide range of influenza viruses circulate in wild birds.However, only two types have ever been known to infect humans. These are two subtypes of the influenza A virus known as (H5N1) and (H9N2). The first human case of the disease was reported in Hong Kong in mid-May .
The outbreak - of the H5N1 sub-type - went on to kill six people and infect 12 others in a small but densely populated area. Nine cases were children under the age of 10.Both viruses were known to be circulating among chickens in Hong Kong, and some of the cases were known to have had contact with poultry before they became ill.
Although it was not possible to establish how every case became infected, it is most likely that the individuals who contracted avian flu did so directly through exposure to chickens.However, there was no evidence of wider spread and no evidence of human-to-human transmission with either strain.
The symptoms of A (H5N1) are very similar to other influenza viruses, typically with fever, malaise, myalgia, sore throat and cough. Conjunctivitis is seen in some patients. Although six of the patients with illness found to be due to influenza A (H5N1) infection died, there is insufficient information to be able to say how severe the illness might have been in the population if it had spread.
Causes were due to:-
1.Poor sanitation of the wholesale markets for poultry and the chicken stalls in the retailed outlets .
2.Chicken stalls and markets in close proximity to the living and playing areas of a great majority of the housing estates
3.No central slaughtering facility for chickens, and the practice of slaughtering chickens at the retailed outlets is highly unsatisfactory.