According to Chinese officials another outbreak of the H5N1 avian flu virus in birds has been found in the northwestern region of the country.

The Chinese Agriculture Ministry says the National Bird Flu Reference Laboratory has identified the virus in samples taken from the town of Xuanhe in Ningxia’s Zhongwei city.

Officials say measures have been taken to prevent the outbreak from spreading, but have not said whether the virus has been found in domestic or wild birds, or how many birds had died.

The last outbreak in the northern province of Shanxi led to the culling of about 1.5 million birds.

Since 2003 the virus has spread among birds across Asia, Europe and Africa and has killed at least 130 people worldwide.

The highest death toll to date is in Vietnam, where 42 people have died.

At present the virus can only be contacted by humans from close contact with sick birds, but there has always been the nagging worry that the virus will mutate into a strain that can spread easily between humans, triggering a worldwide pandemic.

To date China has reported about 40 outbreaks of bird flu in birds across a dozen provinces over the past year, and since November, 12 people are known to have died from the H5N1 strain while six have survived.

The latest human case of bird flu was confirmed on June 15 in the southern town of Shenzhen, near the Hong Kong border, bringing the country’s total human infections to 19.

Meanwhile experts are still attempting to determine whether a Chinese man died of the disease in 2003, two years before the country reported any human cases.

The man was initially said to have died from severe acute respiratory syndrome, (SARS), two years prior to China’s first reported human cases of bird flu in 2005.

Questions have repeatedly been raised about China’s transparency when it comes to informing international health bodies about emerging infections.

The 24-year-old man’s case was given prominence by the disclosure of the cause of his death in a letter to the New England Journal of Medicine by a group of eight Chinese scientists.

Many health experts believe the failure on the part of China to immediately release information about SARS, which appeared in the country’s south in late 2002 contributed to the disease’s spread and cost many lives as a result.

SARS, which has very similar symptoms to bird flu, ultimately killed 774 people worldwide.

The scientists’ letter confirmed that genetic sequencing revealed the death was caused by a mixed virus, with genes similar to two distinct types of bird flu seen in northern and southern China, and raises the possibility that other cases attributed to SARS may in fact have been H5N1 infections.