China is reporting a high incidence of a bone disorder among patients who suffered Severe Acute Respiratory Syndrome. Previously Hong Kong researchers found that SARS patients are at risk of developing avascular necrosis. The new data could signal the problem is more common than first thought.

China's state-owned media reported Wednesday that between 33 to 50 percent of SARS patients could develop a degenerative bone disorder known as avascular necrosis.

Doctors at Beijing's Dongzhimen Hospital say they studied a sample of recovered SARS patients - mostly medical staff who contracted the disease at work.

The World Health Organization says they are looking into reports of the high incidence of the bone disorder.

"Doctors are concerned enough about this? this won't go ignored neither by WHO or other physicians around the world," said Bob Dietz, the agency's spokesman in Beijing. The bone disorder is often found in patients who are treated with heavy doses of steroids. Many SARS patients received steroids to try to control swelling in their lungs. Most SARS patients suffered a severe form of pneumonia.

KY Yeun, a microbiology professor at Hong Kong University, recently said that roughly 10 percent of recovered SARS patients in the city developed avascular necrosis.

He said this figure was almost double the incidence of the disorder in other patients treated with similar steroid doses.

The Beijing research, however, indicates that SARS patients are three to four times more likely to develop avascular bone necrosis than other patients taking steroids.

Professor Yeun in Hong Kong speculates this is because SARS patients' bones were weakened by a lack of oxygen and the steroids only added to the damage.

Eight thousand SARS cases were reported worldwide, two-thirds of them in China and Hong Kong. Globally, about 700 people died before the outbreak faded out in the middle of the year.

On Wednesday, Hong Kong health authorities reported that a man suspected of having SARS had tested negative. It was the first suspected case in the city in more than two months.