Scientists in Hong Kong have claimed a key breakthrough against a virulent form of pneumonia which is claiming more victims around the world.

The researchers have identified the mystery respiratory illness at the heart of a global health scare as a virus from the paramyxoviridae family.

More work is needed to establish whether the virus is a new strain and whether it is curable, according to the doctors from the Chinese University of Hong Kong and Prince of Wales Hospital.

But a university spokeswoman told BBC News Online that the discovery indicated that the treatment being given to patients suffering from the atypical pneumonia in Hong Kong - the hardest-hit area - was the right kind.

Earlier, a spokesman for the World Health Organisation said the longer the virus went unidentified, the more likely it was a new illness.

The body described the illness as a “worldwide health threat” and issued a rare emergency warning after cases were reported on three continents, with more suspected in other parts of the world.

Death toll fears

The latest possible victim of the illness - dubbed Severe Acute Respiratory Syndrome (Sars) - was a doctor in Vietnam who died on Wednesday.

The Frenchman had been involved in the treatment of an American businessman believed to have been suffering from the illness.

A nurse who also cared for the American in Hanoi died earlier.

Authorities in Hong Kong are investigating the death of an elderly man apparently suffering from the atypical pneumonia, the symptoms of which include a high fever, chills, a cough and breathing problems.

If confirmed, the new cases would add to at least 10 deaths believed to have been caused by the outbreak in Asia and Canada.

There are also possible cases in China, where the disease may have originated, and in Germany and Britain among other countries.

The WHO has now recorded 219 people falling ill with the virus, 123 of them in Hong Kong.

If the virus does come from the paramyxoviridae family, researchers could be closer to identifying the best treatment.

“It is an important finding showing the antiviral treatment is the right choice,” said Sydney Chung Sheung-chee, dean of the Chinese University’s faculty of medicine, quoted by the South China Morning Post.