By Sue Ellis
BBC Radio Current Affairs
Every year, the World Health Organisation estimates that 1.3 million people die in the developing world from diseases spread by unsafe injections.
Marc Koska demonstrates his needle
"I was reading a newspaper article one day, and there was one line which said that syringes could be a major transmission route for HIV"
That was 20 years ago and it spurred Marc Koska into a crusade against the spread of disease through the reuse of dirty syringes.
At the age of 23, Koska was a self-confessed 'beach bum'. After leaving school, he'd travelled and indulged his passion for sailing and skiing.
He had ended up in the Caribbean making models of murder scenes which were then used in court.
He realised he was good at representing things with his hands.
Then when Marc read about the risks of HIV transmission through unsafe injections, he set about designing a syringe which was impossible to re-use.
There were already designs for auto-disable (AD) syringes around, but Marc felt they were expensive and difficult to manufacture and use.
He decided he had to produce a syringe that could be made on existing equipment, for the same price as a normal disposable syringe and be used in the same way.
He came up with the K1. With this syringe, the plunger locks and breaks if anyone tries to refill it after one injection.
But it was to take Marc another 17 years before his first commercial sale.
He spent years frustrated by the lack of interest given that he saw his syringe as a way of saving thousands of lives.
It's estimated that half of the 16bn annual injections in poorer countries are done with non sterile syringes or needles.
Often they're often just rinsed in tepid water between injections.
According to Mark Kane, from the Program for Appropriate Technology in Health (PATH), depending on the region, anywhere between 20% and 70% of injections given in developing and transitional countries are potentially dangerous.
Kane has collected data on the problem for the WHO.
In 1999, the first results showed that, every year, about 22m cases of hepatitis B, 2m cases of hepatitis C and 250,000 cases of HIV are being generated by unsafe injections.
"It's a silent epidemic" he said. "An individual who's infected by an unsafe injection may not show symptoms of that infection for 10 or 20 years".
Since 1999, the WHO and UN agencies have made sure that only auto-disable syringes are used in their immunisation campaigns.
But immunisations account for only 5% of the total injections given every year.
All the rest are given for curative reasons (for instance, when someone gets a shot of penicillin from the doctor).
Twenty years on, Marc Koska's syringe is licensed for manufacture in 15 countries across the developing world.
Marc went to the ground-breaking ceremony for the first AD syringe plant to be built in Pakistan.
While he was there, he saw some of the problems caused by unsafe injections.
Hepatitis B and C are Pakistan's big killers. On a visit to Rawalpindi's Social Security Hospital, Marc found almost half the patients on the medical wards were suffering from chronic forms of these diseases.
One woman told him she had no idea how she had contracted hepatitis C, but she had been to a private clinic where she had received injection therapy.
Almost 80% of health care in Pakistan is provided by private doctors, many of them unqualified 'quacks', who practice in rural areas.
Treatment by injection is the norm here. Patients believe that it's far quicker and more effective than tablets.
Doctors, too, find they can charge more for an injection than for pills.
A recent study carried out by the Aga Khan University in Karachi found that injections in health care settings were a major source of hepatitis B and C infections.
Young boys scour rubbish
According to Dr Naveed Zafar Janjua, who carried out the study, "a common view among doctors is, if a needle is not blunt after one use, why not use it twice or thrice?"
And once a syringe has been thrown away, the problem isn't over.
There is a market for syringes, which can either be melted down to make plastics, or, more lucratively, be washed and sold to private doctors to be reused.
At a waste dump in Rawalpindi, Marc came across two little boys, Muhammed and Shah Wali.
Their job is to comb the streets for rubbish, often picking up syringes.
Marc watched in horror as they clutched a bundle of dirty syringes, one of them with blood pouring from his hand.
Legislation is in train to regulate the use of medical devices in Pakistan.
But Marc admits: "Making an AD syringe is just one link in the chain.
"Syringes also have to be made widely available, then disposed of effectively.
"90% of the battle is in information and education, but you have to start somewhere."
Eventually, Marc would like to spread his 'one injection - one syringe' message right across the developing world.
In the meantime, his one link is saving thousands of lives.
It's My Story: Marc Koska - Injecting life will be broadcast on BBC Radio 4 at 2000 GMT on 17 February.