WATCH: The shock moment nyaope addicts demonstrate a blood swap to get high

Nyaope addict Lucas, 27, reaches for a syringe, draws blood from a friend and injects himself. Warning: video contains graphic content not for sensitive viewers.

"When I do not have anything and my friend has a hit he injects himself and then I draw his blood and inject it in myself to get my high," said Lucas, of Soshanguve Block X, north of Pretoria.

"The cravings are so unbearable that you do not care about the risks any more."

A tiny bag of nyaope - which is also known as whoonga and whose ingredients are said to include heroin and antiretrovirals - costs R30.

Lucas has been using nyaope for 10 years.

His veins are in tatters and he says smoking the drug no longer gives him the high it used to, so he has turned to injecting the blood of other users directly into his blood vessels.

This latest vampire-like horror from South Africa's drug world is called "bluetooth", after the technology that connects different digital devices.

• 'Drugs make me forget the pain': Shooting up on Jozi's mean streetsIt's Tuesday morning on Goud Street in central Johannesburg. Jomo's cohorts are injecting two shots of nyaope into his neck. 

But for the addicts practising it, say experts, bluetooth almost certainly means infection with potentially deadly diseases.

Solomon Matejoana, 19, said if there were three addicts, but only a single hit, one user would inject himself with the drug and share his blood with the others.

"We have to do it, otherwise you will not survive the cravings," Matejoana said.

The medical fraternity is shocked by the addicts exchanging blood.

Department of Health spokes-man Joe Maila said experts feared that the HIV transmission rate would skyrocket.

"This creates a huge problem, because there are different blood groupings as well, which might create other medical complications.

"We need to educate people about the dangers of sharing blood. We are very worried about this trend," he said.

The SA Medical Association said the sharing of blood with unsterilised needles was a guarantee of infection.

The prevalence of Hepatitis B and C, as well as HIV, is incredibly high among addicts who use and share needles, said association vice-chairman Mark Sonderup.

"The prevalence is approaching in excess of 80% and it is not surprising with these kind of practices. When you share needles, injecting drugs, you increase the risk. When you draw blood and inject it, you can guarantee infection," Sonderup said.

Addicts like Lucas hang around the dark alleys near Mabopane station in Pretoria.

Female addicts, dying for a fix, sell sex openly in the thin bushes around the railway line.

Sonderup said telling people that they should not do something was not going to solve the problem.

Instead, he said, it was incredibly important to identify vulnerable populations, give them access to screening and link them to care if they are infected.

"People do not want to be sitting on the streets injecting drugs. It is an addiction.

"We have marginalised this group in our society," he said.