Authorities in Shanghai began the mass slaughter of poultry at a market after the H7N9 bird flu virus, which has killed five people in China, was detected there, state media said Friday.

The discovery of the virus in samples of pigeon came as health officials said they were treating a person for flu-like symptoms who had been in close contact with one of the dead, Xinhua news agency reported. There had previously been no evidence of possible human-to-human transmission.

Two more fatalities on Thursday brought the death toll from the virus to five -- four of them in Shanghai -- with the number of confirmed infection cases climbing to 14.

China's Ministry of Agriculture said Thursday the virus had been detected in pigeon samples collected at Huhuai wholesale agricultural market in Shanghai, Xinhua reported.

After gene sequence analysis, the national avian flu reference laboratory found the strain to be "highly congenetic with those found on persons infected with H7N9 virus".

Officials ordered the safe disposal of the culled birds, their excrement and contaminated food, and full disinfection of the market and vehicles used to transport poultry, while attempting to discover where the infected birds had come from.

Meanwhile the live poultry trading areas of another two markets were closed after separate samples showed evidence of the virus.

Chinese authorities are currently trying to determine how the H7N9 virus infects people.

Shanghai health officials said Friday a patient who had been in contact with one of the victims of the virus had been quarantined late Thursday after developing a fever, runny nose and itchy throat.

The first two deaths from the virus, which had never before been seen in humans, occurred in February but were not reported by authorities until late March. Officials said the delay in announcing the results was because it took time to determine the cause of the illnesses.

A 48-year-old poultry transporter was one of two victims reported to have died Thursday, while the identity of the other person was not made public.

Authorities had earlier said none of the eight people whom the 48-year-old had close contact with had shown signs of infection.

The World Health Organisation on Wednesday had ruled out the possibility of a pandemic stating that there was no evidence H7N9 could be transmitted from human to human, unlike the more common H5N1 strain.

But health experts have emphasised the need to quickly identify the source of the virus and its mode of transmission to reduce human exposure.

The more common strain of bird flu, H5N1, killed more than 360 people globally from 2003 until March 12 this year, according to the WHO.

In another development, a man in the central province of Hunan died from H1N1 swine flu on Wednesday, Xinhua reported.

A 2009-2010 swine flu pandemic resulted in over 18,000 deaths worldwide, according to WHO estimates. But the strain, while highly contagious, is not thought to be more lethal than ordinary flu.