`People are terrified." Susan Collins summed up the mood among heroin-users, their families and those working with addicts, at the end of a week which saw the number of young addicts in the Dublin area dying from a "mystery illness" rise to eight.

This is on top of seven other confirmed cases of the illness. It begins with small skin sores and, if left untreated, kills within about 10 days.

Ms Collins is the co-ordinator of Addiction Response Crumlin (ARC), a drug-treatment centre serving the area from which three of the eight people dead came, including the most recent confirmed death, a young woman called Rosemary who died in Beaumont Hospital on Wednesday. "We are worn out with it," says Ms Collins. "Everyone is worn out."

Anna Quigley, co-ordinator of the Citywide Campaign Against Drugs, echoes her sentiments. She describes an overriding sense of "intense anxiety", particularly among the families of users.

Are drug-users behaving differently because of the danger? "Well, perhaps people are being more cautious about where they inject, trying not to inject into muscle. But if their veins have collapsed, addicts are going to inject anyway. There's no point telling a heroin addict not to inject. If it were that easy, we wouldn't have a heroin problem."

This latest crisis among heroin-users first came to the authorities' attention here on May 9th. That Tuesday afternoon the Greater Glasgow Health Board reported an "unusual severe illness" among the city's heroin injectors. Ten days later the board issued a European Infection Warning System, describing the illness and calling on health authorities throughout the EU to seek out similar cases in their areas.

Within days, the Eastern Regional Health Authority, having alerted its acute hospitals, announced that 15 heroin-users had been hospitalised with the "severe unidentified illness", since May 1st.

The illness begins with sores on the skin where the user has injected, followed by localised infection. This is followed by blood infection. Eventually the major organs are engulfed and the body's capacity to maintain life collapses. Some eight have died in this fashion in Ireland, while in Scotland 16 have died since April 26th.

Speculation as to the causes began to circulate as the ERHA urged addicts to refrain from injecting and to present for treatment if concerned about their symptoms. It also set up an emergency helpline.

Meanwhile, an appeal was made to the US Centre for Disease Control and Prevention in Atlanta for help identifying the cause or causes of the illness. Dr Kristey Murray and Dr Jai Lingata arrived, in Dublin and Glasgow respectively, last weekend.

Speculation grew as to whether the infection might be caused by the increasing purity of heroin on the streets (police have been seizing heroin up to 65 per cent pure in the affected cities); whether it might be the large quantities of citric acid addicts are using to dissolve the increasingly pure drug; or whether, as now seems most likely, a bacterium has contaminated the drug.

Isolating the individual bacterium, which would enable microbiologists to develop an anti-toxin, is likely be a "long haul" according to Dr Laurence Gruer, consultant in public health medicine at the Greater Glasgow Health Board, and the man leading its investigation into the illness.

It remains unclear whether this contaminant is a once-off in one batch, or whether it's here to stay.

The Eastern Regional Health Authority has reported an increase in the number of addicts presenting at hospitals concerned about abscesses and sores on their skin. Of the seven cases where addicts were confirmed to have the illness, three have been discharged from hospital and four are still being treated.

There is also a push to get more addicts into methadone treatment programmes. The ERHA announced a rapid expansion of its services on Thursday.

Of the estimated 13,000 heroin addicts in Dublin, about 4,500 are in treatment and 400 are on waiting lists. Almost 8,000 are not in contact with services and are thus least likely to get help should they develop symptoms.

Ms Quigley describes as "hugely frustrating" the apparent fact that it has taken these recent deaths for people - the ERHA included - to regard the heroin situation as a crisis.

"There's a sense that when this hype dies down the urgency will, too. There's a sense that the wider community doesn't really think the heroin-using community matters," she said.

Mr Hugh McGowan of the Clondalkin section of the Coalition of Communities Against Drugs (COCAD) speaks of his community's "rage at the continuing loss of young life, without respite".

Adding that heroin itself is just part of it, he says his community has buried some six addicts, each under the age of 19, who committed suicide in the past month.

Expanded treatment will mean more clinics, which will mean overcoming local opposition. The track record is not good. . Planning permission for the recently opened clinic at Old County Road in Crumlin was first refused following strong opposition from residents.

It was eventually granted two years after the original application, following an appeal to An Bord Pleanala. Permission for a similar clinic in Tallaght was turned down two years ago following vociferous local opposition.

A helpline for anyone concerned about their symptoms is available at 1800 459 459