Asian giant hornets  can grow up to two-inches in length
Asian giant hornets can grow up to two-inches in length (Flickr)  (Flickr)

A rare spate of giant hornet attacks across northwest China has left 42 people dead and more than 1,600 injured, state officials have said.

The wave of attacks broke out in Shaanxi province in July and is still going on.

More than 200 people were being treated in hospital after being stung by the hornets. Many of the victims went into anaphylactic shock and suffered renal failure.

Biologists said Asian giant hornet, which can grow up to 5cm (2ins) in length and has a 5mm long sting, was most likely the culprit.

Most of the attacks occurred in the cities of Shangluo, Hanzhong and Ankkang.

Attacks in rural areas have been blamed by environmentalists on rapid industrialisation of the countryside, which has destroyed the hornets' natural habitat and makes them more aggressive.

Local officials said the dry, warmer weather could also be a factor as it may have led to a sharp rise in the hornet population. During September and October, the hornets naturally become more aggressive when they mate and migrate.

Hua Baozhen, a professor of entomology at Northwest Agriculture and Forestry University, said that the main cause of the upsurge in insect attacks was a decrease in the number of the hornets' natural enemies, such as spiders and birds because of the urbanisation of rural areas, according the Chinese news agency Xinhua.

Local firefighters and police have been given special protective equipment and clothing during the effort to destroy hornet nests.