BEIJING, Nov. 10(Xinhuanet)-- China's Ministry of Agriculture on Thursday informed the country's 800 million rural residents of the ways to prevent and control bird flu through the issuance of an open letter.

In the letter posted on the official website of the ministry, it said in simple language that the epidemic avian flu has hit 15 countries and regions since September, and is yet to be brought under control.

Four provincial areas in China, including the Inner Mongolia Autonomous Region in north China, Anhui Province in east China, Liaoning Province in northwest China and Hunan Province in centralChina, have been hit by the epidemic, according to the letter.

The ministry said the prevention and control of the disease in China faces a"very grave situation," and advised the farmers to enhance their awareness of the disease, improve their capability to prevent the further spread of the epidemic, and take action to prevent any human infection of the bird flu virus.

In the letter, the ministry tells chicken farmers how to keep their henhouses clean, and introduces the basic symptoms of chickens already catching the bird flu.

Farmers were also urged to have their chickens vaccinated and not to buy fake vaccines, and be quick in reporting suspected cases to local vet stations or government departments in charge ofpoultry husbandry.

To date, China has reported four cases of H5N1 bird flu outbreak. Health authorities fear that the more the H5N1 virus spreads, the greater chance it has to mutate-- picking up genes from ordinary flu that could make it highly contagious among humans. Enditem