They say the botulism bug found in the wound of the injecting user in Plymouth could have come from a contaminated supply of heroin.

Health officials are trying to trace the source, and heroin addicts across the South West are being warned that the bug can be fatal in some cases.

Early symptoms include blurred vision and difficulty swallowing and speaking.

Four cases of the potentially-fatal infection were found in users in the Strathclyde and Grampian areas last October.

In 2000, 23 drug users in Scotland were killed by a bug, which blackens the skin and causes liver and kidney failure because of contaminated heroin.