Beijing has taken measures to combat any possible cases of the new strain of avian flu H7N9 in the city, including closing down pigeon markets and banning sales of birds in some pet markets.

Beijing health authorities also gave a public warning Wednesday that all unnecessary touching of wild birds should be avoided. So far, six people have died and 18 have been infected with H7N9 in Shanghai, Anhui, Jiangsu and Zhejiang provinces.

A pigeon salesman surnamed He, who has around 100 birds, said Sunday that pigeon sales were halted and the birds were banned from flying since Friday. Pigeons in a market in Shanghai tested positive for the virus, the Xinhua News Agency reported Thursday.

"I'm not worried about infection, but if I'm ordered to cull my pigeons in the future for public safety, then I will be happy to do so," he said.   

Ma Yanming, media officer of the Beijing Municipal Health Bureau, said that although there are at present no cases of H7N9 in Beijing, they have taken every possible precaution.

"Hospitals should send samples from  patients who have a high fever to one of the 55 laboratories that are capable of doing the testing," he said, noting that all hospitals should inform the corresponding health authorities less than two hours after they find a suspicious case. 

He Quanying, a doctor of respiratory medicine at the Peking University People's Hospital, said that given that H7N9 is a new strain, it is still unknown how it is transmitted.

"We can be sure that this infectious disease comes from birds," he said, noting that pigeon is the only species that is confirmed to be related, but a connection to poultry has not been proven.

Some residents have posted on Sina microblogs that tourists should not get close to birds at Beijing Zoo, but on Sunday, most visitors at the zoo's lake said they were not very concerned.

A tourist surnamed Zhao said that there is no way to prevent infection.

"The disease is spread via birds, which means that whether you are in the zoo or on the street you are at a certain risk of infection," he said, "besides, you can't lock the birds in cages here since it won't be interesting to feed them."

Beijing Centers of Diseases Control and Prevention warned residents Wednesday to always wash hands and keep the indoor air quality fresh. They should reduce contact with birds and ensure meat is fully cooked before eating.

There have as yet been no cases of human-to-human transmission of the virus, Xinhua reported Sunday.