A total of 11 people have tested positive for anthrax
Health officials believe contaminated heroin - thought to be responsible for cases of anthrax in Glasgow - may be circulating elsewhere in Scotland.
It comes after the death of two more drug users with the infection in Glasgow and Tayside.
A total of 11 cases have now been confirmed in Tayside, Glasgow and Lanarkshire with five fatalities.
Test results are being awaited from a female patient in Fife who is currently under investigation for anthrax.
The 11 confirmed cases of anthrax occurred in a male patient in NHS Tayside, three male patients in NHS Lanarkshire and four men and three women in NHS Greater Glasgow & Clyde.
Health officials believe that contaminated heroin or a contaminated cutting agent mixed with the heroin may be responsible for the infections.
Dr Colin Ramsay, consultant epidemiologist at Health Protection Scotland, said: "Evidence now suggests that potentially contaminated heroin may be in circulation in other parts of Scotland, not just the Glasgow area.
"All heroin users need to be aware of the risks contaminated heroin is potentially dangerous taken by any route, not just injection.
"I would advise heroin users to stop using heroin and seek advice from local harm reduction and drug services for support."