Despite repeated medical tests and reassurances from the relevant health authorities, people suffering HIV/AIDS-like symptoms insist they are ill and have been infected with an undetected virus.

Since 2009, there have been thousands of cases in six provinces and municipalities, according to media reports. Victims have complained of HIV/AIDS symptoms despite repeatedly testing negative for the virus.

A leading expert at the Institut Pasteur of Shanghai also backed their claims.

It was unlikely "psychological factors" caused the symptoms, Mo Xiaowei told the Beijing News.

Her institute had conducted blood tests for five sufferers in 2009 and detected "the same unknown virus," Mo said.

Mo's institute, under the Chinese Academy of Sciences, was "unqualified" to conduct such research, the Ministry of Health said.

"I don't agree my symptoms were caused by an AIDS phobia," one man told the Global Times Thursday.

"I was tested negative, but I still have the symptoms. I don't know what I have"

Symptoms include swollen lymph nodes and bleeding under the skin.

The sufferers are fine and most of their symptoms were "exaggerated," Zeng Guang, chief epidemiologist at the Center for Disease Control and Prevention in Beijing, reiterated in a press conference on Wednesday.

His center has done two epidemiological studies and sent blood samples to the US for further testing.

All were found to be HIV negative, and their CD4 cell ratio in the blood - an indicator of the immune system - was found to be normal.

HIV phobia most likely caused the HIV suspicions, said Ministry of Health spokesman Deng Haihua.

The sufferers remained unconvinced.

"I didn't start seeking out doctors until after I discovered the physical symptoms," one sufferer told the Beijing News.