As night envelopes the South African city of Durban, the lights from its port - the largest on the continent - burn a deep orange reminiscent of fire.
From here, and South Africa's other major port in Cape Town, roads thread out across the country, some skirting around the nation's largest city Johannesburg, before heading deep inland, crisscrossing the continent with their cargo.
Fresh fruit and vegetables, raw materials and consumer goods funnel their way into the interior.
However, there's something else hitching a ride. Something deadly. And it's almost as easy to unload as one of the truck's containers.
Its presence is first felt in Jacobs, a scruffy, industrial suburb adjacent to Durban's port where semi-trailers linger, waiting for their cue to move on.
But it could be just as easily picked up at the multitude of border crossings and lay bys that line the route north.
"They use the truck and their own places," a South African sex worker tells news.com.au in Durban. "Where there are always trucks parked you will always find sex workers."
Africa's main roads are highways for HIV. There is still no cure which means, left untreated, those with the virus will inevitably go on to develop, and die, from AIDS.
AIDS deaths are almost unheard of in the west these days but globally a million people died from AIDS last year. Many of those are in Sub-Saharan Africa where the paths of so many sex workers and truckies intersect.
"If I were to show you a map of where our sex work programmes operate it's the major cities and then it's the highways because that's where men congregate," Professor Frances Cowan of University College London, an expert in sexual health in developing countries, tells news.com.au.
She lives and works in Zimbabwe, the country where the main truck routes pass through after leaving South Africa.
"Most goods are transported around that part of the world in big trucks so places like truck stops and border posts are where trucks have to wait en route. Sometimes people can be stuck at the border for a week."
Where truckies stop the danger to their, and other people's health, starts. A proportion of the trucking community are very effectively transporting HIV across Africa, with Zimbabwe the nexus of the epidemic.
"Zimbabwe is the major truck route north for South Africa so the traffic comes up to Harare (the country's capital) and then goes left to Zambia or right to Malawi," says Prof Cowan.
The raw numbers tell a sorry story. One study, in Malawi, found AIDS killed more truckies than malaria or road accidents.
And while the rate of HIV in the Zimbabwean general population is around 15 per cent, in sex workers it can be as high as 58 per cent.
Prof Cowan has helped develop a number of projects in Zimbabwe that have reached out to 80,000 female sex workers. They have undertaken more than 8000 HIV tests, provided 4.7 million condoms and offered counselling and access to treatment - either anti retrovirals to suppress HIV in the body or pre-exposure prophylaxis medication (known as PREP) to help those without the virus to remain that way.
The use of PREP is vitally important to help stop the spread of HIV because while some 70 per cent of sex workers report being able to use condoms with clients, in a third of cases this doesn't happen. Often, it's not for a want of trying.
"Men will pay a lot more for sex without a condom, they say things like 'it's like having sex in a sweetie wrapper,'" Prof Cowan tells news.com.au.
"And some men force them to have sex without them," she says bluntly.
On result of the programs is to boost the number of HIV positive sex workers with undetectable levels of the virus. While it's no cure - the virus returns if treatment stops - it does provide a layer of protection for both the sex worker and client, even if condoms aren't used.
Health service North Star Alliance has 36 clinics dotted across Africa at HIV hot spots along the major highways at borders and ports.
Men will pay a lot more for sex without a condom, they say things like 'it's like having sex in a sweetie wrapper'. And some men force them to have sex without them.
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The organisation targets hard-to-reach populations providing services such as HIV testing and treatment.
"Beyond the reach of traditional health systems, people on the move, like truck drivers and sex workers, are more vulnerable to illness and play a pivotal role in transmitting disease between communities across borders," Bronwyn Cawood, a regional strategist with North Star Alliance tells news.com.au.
"We thought, if they can't get to healthcare, then healthcare needs to get to them."
The clinics are housed in converted shipping containers that can be moved if needed to another location, while finger print identification means medical records can be accessed all over Africa without truckies or sex workers carrying around bulky paperwork.
In an effort to overcome the stigma associated with HIV, the clinics also offer malaria testing and TB screening so truckies can head in without people assuming they have the virus.
Funding is a "big issue" says Cawood. Indeed, there are signs money coming in from rich countries that partly funds these programmes is on the wane.
Other initiatives, such as financial support for teenage girls to stay in school so they aren't drawn into sex work in the first place, are also under threat.
But the biggest hurdle to overcome is the criminalisation of sex work, which remains illegal throughout the region. Sex workers often see the police as persecutors rather than protesters.
"Sex workers face violence, rape and persecution," says Prof Cowan. "They have, in the past, been very unaware of their rights and very unprepared to bring a prosecution in the event they are raped".
The services she works with now employ paralegals to help women if the worst happens.
But battling disease, discrimination and dwindling funding is an uphill battle.
The highway that leads from Jacobs through Africa's heart is still stained with the tears of the young men and women who live, and sometimes die, from a disease we still can't cure.