WHO: H7N9 virus 'one of the most lethal so far'

Hong Kong (CNN) -- As the death toll from China's bird flu outbreak rose to 22 with news of another victim in eastern Zhejiang Province, the World Health Organization warned the H7N9 virus was one of the most lethal that doctors and medical investigators had faced in recent years.

"This is an unusually dangerous virus for humans," Keiji Fukuda, WHO's assistant director-general for health, security and the environment told a news conference in Beijing Wednesday.

"We think this virus is more easily transmitted from poultry to humans than H5N1," he added, referring to the bird flu outbreak between 2004 and 2007 that claimed 332 lives.

"This is definitely one of the most lethal influenza viruses that we have seen so far."

As investigations continue into the possible sources of infection, Fukuda warned that authorities were still struggling to understand the virus. The WHO said China must brace for continued infections.

Fukuda's warning came as Taiwanese health authorities said they've confirmed the first human case of H7N9 in Taiwan -- one they said was imported from China.

A 53-year-old Taiwanese man who worked in eastern China was confirmed to have H7N9 on Wednesday, the Taiwanese Centers for Disease Control said. His condition was described to be severe.

He had been traveling back and forth regularly between China's Jingsu province and Taiwan, health officials said.

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