Bird flu has been identified at a poultry farm in Zoeterwoude, in Zuid Holland province. It is the first case in almost a week and takes the total number of affected farms since the outbreak began to five.

All 28,000 chickens on the farm will be destroyed and tests carried out on the four other poultry farms within a 10 kilometre radius of the affected company. The farm is 20 kilometres from Ter Aar, where avian flu was found a week ago.

Junior economic affairs minister Sharon Dijksma said the new outbreak is a ‘bitter blow’ given the strict measures which have been brought in to control the disease.

It is as yet unclear how the disease reached the five farms, all of which kept their birds inside. Investigations into the origins of the outbreak, including tests on hundreds of wild birds, are continuing.

There is no evidence that intensive poultry rearing is responsible, Dijksma said, referring to an outbreak of avian flu in small scale duck farms in South Korea. In addition, efforts are being made to increase the resistance of factory farmed livestock to disease, the minister told a television current affairs show Buitenhof.

Eric Hubers, chairman of the poultry division at Dutch farm lobby group LTO also said the new case is a major blow. ‘It hurts all the more because we thought we were in a phase where we could begin relaxing the rules,’ news agency ANP quoted him as saying.

Poultry and egg production is a major industry in the Netherlands. Every year over half a billion chickens are slaughtered and at any one time the country is home to 100 million chickens. Most poultry farms are located in Gelderland, Overijssel and Limburg.