They are extremely aggressive and to make matters worse they also spread rapidly from person to person.

Last month the UK had its first documented serious outbreak. A nurse and a patient at a west Midlands hospital died from the PVL form of MRSA, which also infected six other people.

A new study in Science shows just how formidable the bug can be, causing severe pneumonia, inflammation and tissue damage.

Early detection

Professor James said: "The results of this work highlight the urgent requirement for tests that can distinguish hospital acquired MRSA from community acquired MRSA.

"At the moment we have no screening for community acquired MRSA in the community, and no rapid detection of PVL and other toxins in hospital strains of S. aureus in the UK."

Although PVL MRSA is resistant to common antibiotics, other antibiotics are available to treat it, particularly when diagnosed early.

Professor James explained: "It is important to treat the patient with antibiotics that block expression of the PVL toxin as quickly as possible in order to reduce the lung damage."

He called for more funding to research the problem.

Dr Mark Enright, an expert in molecular epidemiology at Imperial College, warned: "PVL strains of MRSA are emerging as a major threat to healthy people of all ages around the world."

The Health Protection Agency has published information to enable GPs and clinicians to recognise potential cases early and to then ensure that laboratory confirmation is obtained, treatment started early and infection control and hygiene advice implemented.