A new strain of bird flu has spread beyond China’s eastern region as reports of human cases reached 60 over the weekend, authorities said.

Two new cases were reported in central Henan province on Sunday morning, while a 7-year-old girl in Beijing was diagnosed with the virus on Saturday, bringing the total number of human infections of H7N9 to 60 people, according to the official Xinhua news agency.

Two more people infected with the avian flu virus died over the weekend in Shanghai where it was first detected. The reported death toll now stands at 13.

The World Health Organization said there was no evidence yet of “sustained human-to-human transmission” of the rare strain of of bird flu. Most of the human cases involved people who had come into contact with poultry.

The agency said it would continue to look for the source of the infection.

“Until the source of infection has been identified, it is expected that there will be no further cases of human infection with the virus in China,” WHO said in an announcement Saturday.

Meanwhile, the strain has hit poultry farmers and restaurants. Fastfood chain KFC said reports of the spread of the virus have had “a significant, negative impact” on its sales in China.