Authorities in Shanghai said on Thursday two more people in the city had died from the rare H7N9 avian flu, bringing the death toll from the littel known virus to five.

At least 14 people have now been found to have been infected with the flu, which has never before been reported in humans and has no known vaccine for its treatment.

The Municipal Health and Family Planning Commission in Shanghai, where two people were reported to have died earlier this week, said two deaths were reported on Thursday, and two cases of infections, Xinhua reported.

One of the deaths was of a four-year-old. The other was a 48-year-old poultry transporter. Authorities had said that eight people who had been in contact with the transporter had shown no symptoms, reiterating that so far, there was no evidence of human-to-human transmission amid rising public concerns.

Earlier this week, four cases were reported in as many cities in the neighbouring province of Jiangsu. On Thursday, a third case was also reported in Zhejiang province, which also borders Shanghai, bringing the number of cases to 14, with six cases in Shanghai and one in neighbouring Anhui province.

With all the cases reported so far in Shanghai and neighbouring provinces, officials said on Thursday health authorities and hospitals in surrounding regions were placed on “high alert” to brace for spreading infections.

Five hospitals in Jiangxi province, which borders Zhejiang, had been ordered to be ready to treat patients, while facilities in the Guangxi Zhuang autonomous region had put in place medical supplies and respirators.

With five deaths out of 14 reported cases — and the remaining patients all said to be in critical condition — the virulent flu has appeared difficult to treat. Authorities, as yet, have not established the cause of the outbreak.

Agricultural authorities said Thursday the H7N9 flu had been detected in pigeon samples in Shanghai, suggesting they may have been carriers.

The government has called on the public to refrain from slaughtering poultry to minimise exposure. Thursday was a national holiday in China — marked as “tomb sweeping day” – during which many Chinese, particularly in rural areas, offer poultry to remember their ancestors.

In China, memories of the SARS outbreak from a decade ago — which left at least 350 people dead in China and a further 299 deaths in Hong Kong — and more recent health safety issues have left the public wary of an official response that is often seen as downplaying concerns and delaying the release of information.