The health authority in Fujian is investigating the cause of HIV in a five-year-old girl who her parents insisted was infected during an operation four years ago.

Maomao, who has congenital heart disease, was found to carry the deadly virus during a physical examination in September 2014.

After her parents were cleared of HIV infection, the one and only evidence they could think of pointed to an operation Maomao had when she was eight months old.

The operation performed by the Fuzhou Xiehe Hospital in 2010 was declared to be a success at the time. But the parents said Maomao has been weak and prone to illness.

Her conditions worsened in Aug 2014 and she caught a very high fever. She was then diagnosed with the HIV infection in Sept.

An employee with the hospital told Chinese Business that the hospital bears no responsibility because the blood was provided by the Fujian Blood Center which is supposed to meet national standards.

The Center insisted the blood for Maomao’s operation was qualified. But it can’t rule out the possibility of a blood donor was in a “window period”, which refers to the time from infection until a test can detect any change.

The provincial health authority has traced down all of the eight blood donors involved in Maomao’s operation. The results showed one of them did have HIV.

“It doesn’t mean there is necessarily a connection. All we can say right now is that the possibility is very high,” according to an insider.

Ms Zeng, Maomao’s mother, said the family has become debt-ridden since the medical fees have piled up to more than 300,000 yuan.

“I only want my child to be healthy,” she said.