A deadly stomach bug that has killed thousands in North America and Europe is in Melbourne, the Herald Sun reported Wednesday.

A private Melbourne hospital confirmed Tuesday that three elderly patients had been infected with the killer strain and it was likely to be more widespread.

Epworth Hospital executive medical director Megan Robertson said this hypervirulent strain of Clostridium difficile had not been previously detected in Australia.

"But having said that the testing in Australia is very limited,'' Dr Robertson said.

"The hypervirulent strain is quite difficult to get tested in Australia, and in fact we had to send our specimens to a laboratory in Western Australia.''

She said the three patients to test positive were potentially just the tip of the iceberg across the country.

It was a cause for concern because the virus was increasing in virulence and highly infectious, she said.

The bug has been noted extensively through North America, Europe and the U.K. for at least the last two years.

It is also known as the Quebec strain after it killed 1,270 people in the Canadian province in 2003, and caused 8,324 deaths in Britain in 2007.