They are part a key and complex transport web in Southern Africa, this steady stream of trucks pulling into and out of the truck stop at the Mwanza border post - at any moment there might be as many as 50 trucks waiting to cross the border. Their drivers have been on the road for up to four weeks, hauling the fuel and goods so essential to the region's economies; and, the food and medicine for those suffering the consequences of crop failures, chronic poverty and HIV/AIDS.
But often they carry something else, dangerous to themselves and those with whom they are intimate - sexually transmitted infections or STIs, and HIV, the virus that causes AIDS.
A 2001 South African study found the prevalence of HIV among truck drivers was 56 percent and in some cases as high as 70 percent; and in female sex workers at the truck stops it went as high as 74 percent. In Malawi one trucking company lost 83 drivers out of 100 to AIDS.
In response, South Africa launched a network of so-called Wellness Centers at truck stops, where drivers and sex workers have access to education on STIs and HIV, free condoms, and treatment for STIs. The program has spread to several countries.
Using a flip chart with explicit images, the center's education officer, Medson Mulenga, demonstrates, explains and answers questions on STIs and HIV. He says the visitors are most interested in learning why it is important to avoid and treat STIs as a means of preventing HIV infection.
"Almost daily, about five, six people ask about HIV/AIDS," said Medson Mulenga. "On HIV/AIDS, most usually what they ask is on VCT, which means voluntary counseling and testing. They ask if we are offering any VCT, and because we have not yet started offering VCT, we just generally educate, each other, one another, on HIV/AIDS prevention, and the like."
Cleofas Magwire is the clinical officer at the two-room center at Mwanza. He tells VOA that he is able to treat drivers and sex workers with a range of complaints from headaches and diarrhea caused by long hours and a poor diet, to STIs. But he says, he cannot test for or treat HIV/AIDS and pleads for the resources to be able to do so.
"If we could get assistance for other drugs, so that we should be treating other illnesses like HIV/AIDS related illnesses, including skin infections," said Cleofas Magwire. "Also HIV/AIDS we should be treating them here. Because last time I had two patients, who were on ARVs from Zimbabwe, so they were complaining they don't have ARVs [anti-retroviral drugs], they have completed them, so they do not know where to get them. So if we could get ARVs here, and we could be treating HIV/AIDS here, that would be better."
In the two months since it was opened, the Mwanza Wellness Centre has become popular with drivers, sex workers and people from the surrounding communities.
Driver Sanford Seleman, who has been a trucker for 10 years, says that even though he has not yet had to make use of the center, many of his friends have.
"That program is very good enough," said Sanford Seleman. "Its helping almost all the drivers getting some problems on the way if they reach this place, they get help."
Sex workers at the truck stop, while willing to speak to male visitors, were reluctant to talk about their lives to a female visitor. But they said briefly, that their lives were hard and that to make a living they need around three clients a night. They also said center was useful to them because of the free condoms.
Visitors from the surrounding community are the most eager to speak of what the center means to them.
Charity Tangata, a vivacious 22-year-old, tells VOA she is a frequent visitor and and has learned a lot about STIs and HIV at the center - knowledge she says she shares with her friends and neighbors.
"There is that chance to say once she has visited the place, and then she goes out home, she chats with different friends and then she introduces to them what she has learned here," said Charity Tangata. "Let us say on using the condom, if one is not trusted in her relationship, then she should insist on using a condom, and telling them messages to say it is not proper to get into early sex before marriage and how to prevent HIV/AIDS diseases, and other sexually transmitted diseases."
George Mantawara tells VOA he too has learned a great deal from his regular visits to the center; adding that he had no idea there was so much to learn about using a condom.