Part of complete coverage on
Scientist: Poultry trade may be spreading deadly bird flu
May 6, 2013 -- Updated 0835 GMT (1635 HKT)
Evidence suggests that poultry markets like this one could be the primary source of human infection with H7N9, an expert says.
- Virologist says poultry trade may be spreading deadly bird flu virus
- Evidence that wet markets selling live poultry are primary source of infection
- 127 cases have been detected in 10 provinces and 24 people have died
- Poultry markets closed in Shanghai and six other provinces
Hong Kong (CNN) -- Poultry workers moving to and from wet markets and farms may be responsible for the spread of the deadly H7N9 virus in China, says a virologist who's working with the World Health Organisation to investigate the outbreak.
University of Hong Kong clinical virologist Malik Peiris told CNN the closure of Shanghai's poultry markets on April 6 had resulted in a sharp drop in the number of human cases in the city.
"That is clear evidence that the poultry markets are the primary source of human infection," he said.
Peiris, who visited regions hit by the virus as part of a joint WHO mission last month, added that studies of earlier H5N1 bird flu outbreaks in Hong Kong had shown that the virus can move between live poultry markets and clean farms through contaminated cages and other exposed items, and this was a likely explanation of how the virus was being transmitted around China.
"That's how this infection can keep on zigzagging in this way," he said.
READ: Hong Kong tightens bird flu defenses
Virologist: Bird flu 'cause for concern'
New bird flu spreads outside China
WHO: Bird flu outbreak especially lethal
Since H7N9 was first identified in March, 128 cases have been detected in 10 provinces and 26 people have died, according to figures released on May 2 by the WHO.
In addition to markets in Shanghai, China has also temporarily closed live poultry wholesale markets in Jiangsu, Fujian, Jiangxi, Anhui, Guangdong and Zhejiang provinces.
Health authorities are still investigating the possible sources of infection and Peiris said there was still much work to be done on how the virus had jumped to humans and how it was being spread.
WHO assistant director general Keiji Fukada said in a press conference in Beijing on April 24 that H7N9 was one of the most lethal influenza viruses seen so far and unusually dangerous for humans.
The international health body has stressed there is no evidence of sustained human-to-human transmission of the virus, but Peiris said that it was difficult to ascertain whether clusters of cases within the same family were the result of "limited human-to-human transmission or whether these people have been exposed to the same source" -- such as by visiting the same live poultry market.
READ: Bird flu: 5 things to know
A large-scale study of blood samples being conducted in China would shed light on whether there had been milder or undiagnosed cases of H7N9 in the wider population -- a key factor in determining the mortality rate, said Peiris, who played a key role in identifying the virus that caused SARS.
"Even if there is limited human-to-human transmission, that doesn't necessarily have any dire consequences because limited human-to-human transmission has been reported for a long time with H5N1."
The visible impact of the virus could also reduce as the hot summer weather approaches but it was unlikely to die out and might re-emerge in winter, Peiris added.
CNN's Fang Ke and Zhang Dayu contributed to this report from Beijing
Part of complete coverage on
August 19, 2014 -- Updated 0513 GMT (1313 HKT)
Chinese are turning to overseas personal shoppers to get their hands on luxury goods at lower prices.
August 15, 2014 -- Updated 0908 GMT (1708 HKT)
Experts say rapidly rising numbers of Christians are making it harder for authorities to control the religion's spread.
August 11, 2014 -- Updated 0452 GMT (1252 HKT)
"I'm proud of their moral standing," says Harvey Humphrey. His parents are accused of corporate crimes in China.
August 6, 2014 -- Updated 1942 GMT (0342 HKT)
A TV confession detailing a life of illegal gambling and paid-for sex has capped the dramatic fall of one of China's most high-profile social media celebrities.
July 31, 2014 -- Updated 0410 GMT (1210 HKT)
President Xi Jinping's campaign to punish corrupt Chinese officials has snared its biggest target -- where can the campaign go from here?
July 30, 2014 -- Updated 0712 GMT (1512 HKT)
All you need to know about the tainted meat produce that affects fast food restaurants across China, Hong Kong, and Japan.
July 18, 2014 -- Updated 0230 GMT (1030 HKT)
Some savvy individuals in China are claiming naming rights to valuable foreign brands. Here's how companies can combat them.
July 16, 2014 -- Updated 0911 GMT (1711 HKT)
Is the Chinese president a true reformist or merely a "dictator" in disguise? CNN's Beijing bureau chief Jaime FlorCruz dissects the leader's policies
July 8, 2014 -- Updated 0344 GMT (1144 HKT)
With a population of 1.3 billion, you'd think that there would be 11 people in China who are good enough to put up a fight on the football pitch.
July 4, 2014 -- Updated 0631 GMT (1431 HKT)
26-year-old Ji Cheng is the first rider from China to compete for competitive cycling's highest honor.
July 7, 2014 -- Updated 1124 GMT (1924 HKT)
China's richest man, Wang Jianlin, may not yet be a household name outside of China, but that could be about to change.
July 3, 2014 -- Updated 2357 GMT (0757 HKT)
When President Xi Jinping arrives in Seoul this week, the Chinese leader will have passed over North Korea in favor of its arch rival.
July 1, 2014 -- Updated 0656 GMT (1456 HKT)
The push for democratic reform in Hong Kong is testing China's "one country, two systems" model.
June 30, 2014 -- Updated 1156 GMT (1956 HKT)
Along a winding Chinese mountain road dotted with inns and restaurants is Jinan Orphanage, a place of refuge and site for troubled parents to dump unwanted children.
June 26, 2014 -- Updated 0836 GMT (1636 HKT)
CNN's Kristie Lu Stout invites Isaac Mao, Han Dongfang, and James Miles to discuss the rise of civil society in China and social media's crucial role.
June 26, 2014 -- Updated 0334 GMT (1134 HKT)
Chen Guangbiao wants rich people to give more to charity and he'll do anything to get their attention, including buying lunch for poor New Yorkers.
June 26, 2014 -- Updated 1144 GMT (1944 HKT)
Architects are planning to build the future world's tallest towers in China. They're going to come in pretty colors.
Today's five most popular stories