The Irish Examiner has learned there has been nine new cases among injecting addicts in the city so far this year, compared to almost no cases in the same period last year.
The HSE said they are still investigating the scale of the increase, but had identified 13 new cases since June 2014.
While the cause of the rise is not clear, it may be linked to the injection of the former head shop drug mephedrone, and abuse of tranquillisers called benzodiazepines.
GPs and drugs workers believe this may be contributing to a chaotic lifestyle, resulting in the sharing of injecting equipment and unsafe sex, the primary routes for transmission.
A HSE alert, seen by the Irish Examiner, states: “The Department of Public Health HSE East is investigating an increase in the number of new cases of recently acquired HIV in Persons who inject drugs (PWID) in Dublin in 2015.”
It said a multidisciplinary incident team had been set up, to “investigate and respond to this increase”.
Dr Austin O’Carroll, a city GP and HSE team member, said: “There has definitely been an increase in the detection of HIV cases in homeless people using drugs.”
He said there were indications the problem may be confined to a group of linked people. He said it was well known the causes were the sharing of injecting equipment and unsafe sex.
Dr O’Carroll said possible reasons could be the intravenous use of mephedrone, also known as snow blow.
He said this made users “agitated” which could lead to unsafe practices. The trend of users taking “high doses of benzos” could also be a factor , as well as the homeless crisis, with more people on the streets.
Tony Duffin of the Ana Liffey Drug Project said that the figures were “really worrying”. He suspected the rise was among a group of chaotic users who were injecting mephedrone.
“If you have a particularly bad mephedrone habit you can inject up to every two hours,” he said. “That means more injecting, more blood and more opportunity for sharing equipment. There also appears to be heightened sexual activity.”
A HSE spokeswoman said the team was identifying risk factors and control measures.
Drugs/HIV Helpline 1800 459 459