Image copyright SPL Image caption In both cases to date, the infection was acquired in the Middle East

A new respiratory illness - from the same family as the Sars virus - appears not to spread easily, experts at the World Health Organization (WHO) say.

A Qatari man, 49, with the virus is being treated in London. The first person known to have had it, in Saudi Arabia, died.

The WHO said on Friday that it appeared the new virus "cannot be easily transmitted from person to person."

The Sars virus, which emerged in China in 2002, killed hundreds of people.

Both Sars (severe acute respiratory syndrome) and the new, un-named, virus - as well as the common cold virus - belong to the coronavirus family

But this new virus is different from any coronaviruses previously identified in humans.

Both of the patients known to have had the virus experienced kidney failure.

Zoonotic

The WHO said it would continue to monitor the situation but was not recommending any travel restrictions for Saudi Arabia or Qatar.

However it said it was working closely with Saudi authorities in advance of the forthcoming Hajj, the annual Muslim pilgrimage to Mecca.

The WHO also announced diagnostic tests were being developed by scientists around the world as quickly as possible.

The European Centre for Disease Prevention and Control (ECDC), which monitors disease in the European Union, said initial findings suggested the virus may have originated in animals - diseases known as zoonotic.

Writing in the journal Eurosurveillance, they said: "It is quite probably of zoonotic origin and different in behaviour to Sars."