A man infected with H7N9 bird flu receives treatment at an intensive care unit in a hospital in Kaifeng, Henan province, on Sunday. Li Bo / Xinhua

Sustained transmission among humans is concern: WHO official

There is no evidence so far of sustained human-to-human transmission of H7N9 bird flu virus, World Health Organization representative to China Michael O'Leary said at a news briefing on Sunday in Beijing.

O'Leary's comment followed reports of a married couple in Shanghai being infected with the virus.

The 56-year-old man was diagnosed with H7N9 bird flu after his wife died from the infection.

It's difficult to determine whether the man got the virus from his wife or from the same source of infection his wife was exposed to, "but that's part of the very active investigation", said O'Leary.

If there are only very rare cases of human-to-human transmission, that is different from sustained person-to-person transmission, he said.

Sustained human-to-human transmission raises the risk of a pandemic, medical experts said.

"It's that easy and sustained transmission among humans that we are concerned about, and there is no evidence of that yet," O'Leary said.

With influenza, for example, 20 to 30 percent of a patient's family members could be expected to develop the illness, according to medical experts.

There was insufficient information to determine whether the man was infected by his wife, according to the Shanghai health authority.

Authorities were investigating cases of human infection with H7N9 within a family or involving people unexposed to birds, it said.

Other key information like the transmission dynamics, modes of transmission, the scope of the problem and the severity also needs to be clarified through investigation, said Feng Zijian, director of the emergency response department at the Chinese Center for Disease Control and Prevention.

Feng said that sporadic individual cases of human-to-human transmission would not necessarily mean the virus can be transmitted effectively among humans.

Surveillance of people who have close contact with patients, particularly family members and healthcare providers, will be enhanced to help determine whether human-to-human H7N9 transmission is efficient or sporadic, Feng said.

However, the gene sequences of the new variant on H7N9 that is infecting humans indicated it might be better adapted than other bird flu viruses to infecting mammals, according to an article on the New England Journal of Medicine website.

That article, Human Infection with a Novel Avian-Origin Influenza A (H7N9) Virus, by Chinese scientists, was published by the renowned medical journal online on Saturday, Beijing time.

It was a joint effort by China's public health department, hospitals, universities, and research institutes, China's CDC said in a statement.

The new reassortant avian-origin influenza A (H7N9) virus was found to be associated with severe and fatal respiratory disease in human patients, the article said.

The transmission spreading dynamics of the variant H7N9 strain couldn't be underestimated and the source of infections remains unknown, it said.

As of Sunday, 60 people had been reported infected with H7N9 in China and 13 had died, according to regional health authorities.

Beijing and Henan province reported their first H7N9 human cases over the weekend, showing the virus had traveled north.

All of the previous cases were East China, including Shanghai and the adjoining provinces of Jiangsu, Anhui, and Zhejiang.

Deng Ying, director of Beijing CDC, said a risk assessment shows the capital faces challenges in containing the spread of the virus, particularly from incoming travelers infected and infected migrant birds flying northward.

A notable difficulty is that the virus only causes mild illness in animals, according to Tom Frieden, director of the US CDC.

That makes it more difficult to intervene, he said.

"Sometimes when there are things like outbreaks of H5, you have a clue because there are bird die-offs or sick flocks," he said.

Contact the writers at shanjuan@chinadaily.com.cn and wangqingyun@chinadaily.com.cn

(China Daily 04/15/2013 page3)