Hong Kong (CNN) -- Swarms of aggressive hornets, in their fall mating season, are inflicting a deadly toll in a central Chinese province.
Hornets have killed 42 people and injured 1,675 people in three cities in Shaanxi province since July, according to the local government. Thirty-seven patients remain in critical or serious condition.
Over the summer and early fall, hornets have invaded schools full of children and descended upon unsuspecting farm workers in China.
One of them is Mu Conghui, a woman who was attacked in Ankang City while looking after her millet crop.
"The hornets were horrifying," she told Xinhua, the Chinese state-run news agency. "They hit right at my head and covered my legs. All of a sudden I was stung and I couldn't move.
"Even now, my legs are covered with sting holes."Killer hornets sting nearly 600 people Two months, 13 dialysis treatments and 200 stitches later, Mu still remains hospitalized and unable to move her legs.
The influx of venom to the human body can cause allergic reactions and multiple organ failure leading to death. Patients like Mu have been receiving dialysis to remove the toxins from her body. In photos, patients bore deep dark craters scattered across their limbs, the size of bullet wounds.Government authorities say these attacks are from a particularly venomous species, the world's largest hornet, known as the Asian giant hornet or vespa mandarinia.The giant hornet extends about 3.5 to 3.9 centimeters in length, roughly the size of a human thumb. It has an orange head with a black tooth used for burrowing, according to an animal database at the University of Michigan.Dr. Wang Xue, director of the intensive care unit at First Affiliated Hospital of Xi'an Jiaotong University and an expert of the provincial hornet sting treatment guidance unit, warned in a Shaanxi government release that hornets tend to be aggressive and more active during September and October -- their breeding season. The hornets do not go into hibernation until December, according to local government authorities.
Local authorities have deployed thousands of police officers and locals to destroy the hives. So far, about 710 hives have been removed and at least 7 million yuan (about $1.1 million U.S.) sent to areas affected by hornets, according to a government press release.The spate of attacks could be caused by the unusually dry weather in the area, authorities say. The arid environment makes it easier for hornets to breed. Urbanization could also be a contributing factor, as humans move into hornets' habitats. Some experts cited in Xinhua stated additional factors such as increased vegetation and a decrease in the hornets' enemies, such as spiders and birds because of ecological changes.Humans can inadvertently irritate the hornet hives, as most are tucked away in secluded places, such as tree hollows or even underground.
About 30 to 50 deaths are reported each year in Japan from such attacks, according to Japanese studies. Most of the deaths are due to allergies to the venom, said Shunichi Makino, director general of the Hokkaido Research Center for Forestry and Forest Products Research Institute."It's very difficult to prevent the attacks because hornet nests are usually in hidden sites," he said.
Makino, who specializes in entomology, warned that the sting from an Asian giant hornet was severe compared with those of other insects.
"The venom of an Asian giant hornet is very special compared with other hornets or yellow jackets," he said. "The neurotoxin -- especially to mammals including humans -- it's a special brand of venom."
The giant hornets are also destructive to western honey bees. Research in Japan suggests tens of thousands of honey bee hives are damaged by the giant hornets each year. The species feed their young with the larvae of other insects and use their mandibles to sever the limbs and heads of their prey. The hornet's venom sting is a neurotoxin so powerful that it dissolves human tissue, according to the Guinness Book of World Records.The giant hornets are attracted to human sweat, alcohol and sweet flavors and smells. They are especially sensitive to when animals or people run, according to Xinhua.
One victim told local media earlier this month that "the more you run, the more they want to chase you." Some victims described being chased about 200 meters (656 feet) by a swarm.
Every breeding season, the giant hornets produce an average of 10,000 offspring. They feast on other insects such as wasps and bees, launching coordinated attacks on the hives of their prey.