The Health Protection Agency has confirmed that another person has been diagnosed with anthrax after injecting heroin.
The user, from Oxford, is currently recovering from the infection, and is the fifth person in the UK to be diagnosed with anthrax during the current outbreak.
Two people died from the infection in Blackpool in August and September.
Anthrax is a very rare but serious bacterial infection. Drug users are at risk of being infected when heroin is contaminated with anthrax spores.
Symptoms may include swelling, redness, an abscess or an ulcer around the injection site, as well as septicaemia and meningitis.
There is currently a pan-European outbreak of anthrax among drug users who inject. The source of infection is thought to be contaminated heroin.
Dr Fortune Ncube, a HPA expert in infections among users who inject drugs, said: "Anthrax can be cured with antibiotics, if treatment is started early. It is therefore important for medical professionals to be alert to the possibly of anthrax infection in heroin users presenting with signs and symptoms - which include severe soft tissue infections or blood poisoning - to prevent any delays in providing treatment.
"It is possible that further cases may be seen in people who inject heroin. People who use drugs may become infected with anthrax when the heroin they use is contaminated with anthrax spores.
"This could be a source of infection if injected, smoked or snorted - There is no safe route for consuming heroin or other drugs that may be contaminated with anthrax spores."
Dr Eamonn O'Moore, director of the HPA's Thames Valley Health Protection Unit, said that local drug and alcohol teams have been advised to inform users who inject drugs about the risk of anthrax.
"Injecting drug users often experience skin infection but we strongly advise them not to ignore signs such as redness or excessive swelling around injection sites, or other symptoms of general illness such a high temperature, chills, severe headaches or breathing difficulties," he said.
"They should seek medical advice quickly in such circumstances generally, but particularly now because we have concerns that some batches of heroin in circulation in Oxfordshire and the wider Thames Valley may be contaminated with anthrax. Early treatment with antibiotics is essential for a successful recovery."
On 30 October, the HPA was awarded a £4 million contract by the US government to develop a new vaccine for anthrax. While it is extremely rare in humans, attempts have been made the weaponise the infection.
In 2001, letters containing anthrax spores were sent through the US postal system and resulted in 22 human cases. As a result, governments across the globe have invested significant resources to ensure they are prepared for the deliberate release of anthrax.