The European Centre for Disease Prevention and Control (ECDC) said infections with the AIDS-causing virus among drug users and other high-risk groups were rising fast, and that a failure to act would mean far higher costs in future.

ECDC director Marc Sprenger will meet Greek officials this week to say that free needles, syringes and opioid substitution projects must be stepped up, and testing and treatment for the human immunodeficiency virus made available to all.

"Immediate concerted action is needed in order to curb and eventually stop the current outbreak," he told Reuters as the ECDC published a report on Greece's HIV problem.

Since 2009, recession in Greece has reduced economic output by a fifth and sent unemployment to a record high.

The healthcare system is under extreme pressure, making it harder for the poor, unemployed or homeless to get treatment.

While Greece has only 7.4 HIV infections per 100,000 people, compared to 10 per 100,000 in Britain or 27.3 in Estonia, rates have soared since 2011 in high-risk groups such as drug users.

From 2007 to 2010, there were only 10 to 15 cases a year of HIV infection in injecting drug users.

But during 2011, there were 256 such cases - or 27 percent of the total. Another 314 were reported between January and August 2012, most of them in the capital.

Combination drugs can give patients with HIV near-normal life expectancy, but the drugs must be taken for life, and cost 10,000 to 22,000 euros ($13,000 to $28,500) a year. Sprenger said Greece's costs were at risk of running out of control.

"If a scale-up (in prevention and testing) is not achieved, it's likely that HIV transmission among people who inject drugs in Athens will continue and even accelerate - and could eventually spread," he said.

"The cost of prevention ... will be significantly less than the provision of treatment to those who become infected."

The ECDC said it was unclear how much Greece's debt crisis has contributed to HIV outbreak.

Rates of other health problems such as depression and suicide have been rising in Greece, which is also battling the re-emergence of mosquito-borne diseases such West Nile Virus and malaria.

(Reporting by Kate Kelland; Editing by Kevin Liffey)

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