Scientists believe more cases of the potentially disease will emerge over the coming days.
The Food Standards Agency has said that bird flu does not pose a food safety risk for United Kingdom consumers.
Public Health England said the risk to the public is very low.
The disease is highly contagious among birds and bird owners and farmers have been warned to be vigilant and maintain good biosecurity.
Defra has now declared a prevention zone around the affected area, which is close to the village of Abbotsbury. This means wild birds carrying the disease can infect domestic poultry, so the best way to reduce the risk of your poultry catching bird flu is to minimise chances for them to come into contact with wild birds or their droppings by practising good biosecurity.
Anyone inside the zone who keeps captive birds has been told to feed and water their animals inside and disinfect their footwear when moving in and out of enclosures.
Any unexplained deaths or sickness in their birds should also be reported to a vet immediately.
The ministry said the current strain is different to that which affected people in China past year.
Poultry farmers in the South Dorset area of the United Kingdom have been put on high alert for bird flu.
The virus, which is also known as avian flu, is a type of influenza that mainly affects birds but can sometimes pose a threat to humans. The strain, however, is the European strain, as opposed to the Asian strain, which is not associated with humans.
Last year, The World Health Organisation confirmed that 840 people had been infected by the H6N1 virus worldwide by May 2015 and 447 of the cases were fatal.
Different strains of bird flu can spread to people when they have direct contact with the infection.
Symptoms of bird flu include high temperature, aching muscles, headache, respiratory problems, diarrhoea and vomiting, abdominal pain, chest pain and nose and gum bleeding.