Half of the HIV cases being treated in Malta involve African immigrants, who make up just one per cent of the population, The Sunday Times has learnt.

New HIV-positive cases have quadrupled - from between seven and 10 cases a year to about 30 to 40 - in the past two to three years, coinciding with increases in the number of illegal immigrant landings.

Christopher Barbara, Malta's only virologist in service and chairman of Mater Dei Hospital's Pathology Department, has expressed concern about a problem which he insists cannot be ignored. There are currently 100 people being treated for HIV within the Malta health services, and half of these are immigrants.

Dr Barbara pointed out that illegal immigrants were coming from high-risk populations and people should be knowledgeable about the dangers of having unprotected sex.

Sub-Saharan Africa is more heavily affected by HIV and AIDS than any other region in the world, according to the UNAIDS 2008 report. An estimated 22 million people were living with HIV at the end of 2007 and approximately 1.9 million additional people were infected during that year. Dr Barbara drew parallels with the re-emergence of syphilis, another sexually transmitted infection, in the past decade.

The disease had practically been eradicated, but promiscuous behaviour by young Maltese who slept around with tourists meant it made a comeback. Syphilis is a very common infection in eastern Europe.

Dr Barbara said: "It is all about education. There are infections which are endemic to certain countries. If, for example, you're travelling to some areas in north Africa you are advised to take a vaccine against hepatitis A. Once you get people coming in carrying certain diseases there is a risk of infection and you can't just go and have sex with anyone."

He pointed out that many illegal immigrants were unwitting carriers of HIV, and could in certain cases have contracted it innocently at birth.

"The point is we're receiving several people who look very healthy, but can be carrying a virus that can be transmitted to others - via the sexual route, via blood or blood-borne infections, and from mother to child," he said.

He said that upon arrival, immigrants underwent medical examinations, with a particular focus on screening for tuberculosis, through chest X-rays and skin lesions.

Although no blood tests were taken to establish whether individuals were infected with HIV, Dr Barbara doubts whether this is a practical or ethical solution to the problem.

"We cannot have a situation where somebody reaches the island and we'll just push in a needle, take blood and test them."

Parliamentary Secretary Joe Cassar said when contacted that the government was addressing this issue and taking advice from consultants on the best way forward.

Dr Barbara also pointed out that while screening was not expensive, treating an HIV-positive patient was - costing approximately €500 a month. Patients need to take this treatment for life to prevent the virus developing into full-blown AIDS.

People on medication are also potentially still infectious to others, albeit less so, until the viral load goes down.

"Even if we get all the money in the world to fund this, we still need specialists in infectious diseases to administer the antiviral drugs. We only have two such people in Malta," he said.

He also said that counselling facilities were required if a policy was adopted to conduct widespread screening, to prepare individuals for the consequences.

"If the test is positive we have to offer treatment. Otherwise, why are we screening them in the first place? And it would be ethically incorrect to screen somebody selfishly just so that we can label them HIV-positive."

Dr Barbara said it was also important for patients undergoing treatment to comply with the strict regime, since medication had to be taken at a specific time three or four times a day.

"If you're not compliant with your treatment, a few of the organisms in the blood will become resistant to the drug and you get the emergence of resistant strains," he pointed out.

Asked if the immigrants undergoing treatment were compliant, Dr Barbara said specialists were facing huge problems.

"They start the treatment. Then they don't turn up at the clinic and don't collect their medicine, so there's the risk of resistance. They're having a lot of problems," he said.

Realistically, does he believe screening immigrants for HIV can work?

"It all depends on the individual, that's why it's important to counsel them first.

Maybe they're not interested, maybe they feel this is something they live with and they've accepted that their lifespan is 30 years. It's all traditionally related to what these people want, so it's not just a matter of resources.

"As a Christian I'm obliged to help but will it backfire on our population if they don't take treatment correctly? That's where a bit of selfishness gets into it. I'm doing all I can to help, but if they're not complaint, instead of helping the situation I would create a multi-drug resistant strain in Malta, which we may not be able to treat. "I'm still not convinced screening is the solution. Initially, I thought we should help these people and treat them. Today, the more I study the situation the more convinced I am that we shouldn't."

However, he added, screening of selected ideal candidates who might be compliant to treatment could be a solution, but more scientific studies and help from modellers would be required.