Sub-Saharan Africa is an ideal transit area in the international drug trafficking network. Increasing volumes of illicit drugs, particularly heroin and cocaine, are being shipped through the region en route to their final destination: the thriving markets of Europe and North America.

With lax border controls, inadequate law enforcement, and growing international transport connections and trade links, it was only a matter of time before traffickers took notice. In its 2007 World Drug Report, the UN Office on Drugs and Crime (UNODC) warns that Africa "is increasingly being exploited by drug traffickers, and this trend can be expected to continue."

Some of these drugs are now being taken up by an expanding domestic market, particularly along key drug-trafficking routes. According to UNODC, the demand for heroin - the number one drug of choice for injecting drug users (IDUs) - has shot up in countries like Mozambique, Kenya and Tanzania, and is slowly rising in South Africa, Madagascar, Ghana, Liberia and Senegal.

An overlooked epidemic

This does not bode well for a region often described as the "global epicentre" of the HIV/AIDS pandemic. Sharing syringes is a very efficient way to transmit blood-borne viruses such as HIV, and has been found to be three times more likely to transmit the virus than sexual intercourse.

Apart from sharing needles and syringes, IDUs may also engage in risky sexual behaviour, and are sometimes driven to trade or sell sex to support their habit.

Once HIV enters a population of IDUs, the spread of the virus tends to be explosive and then it easily moves into the general population. Injecting is not the only form of recreational drug use that increases the risk of HIV transmission: non-injecting drug users can also be exposed to the virus by unsafe sexual behaviour when they are high.

Sex is the main route of transmission of HIV in sub-Saharan Africa, so injecting and non-injecting drug use have largely been ignored in the response to HIV/AIDS.

But the alarm bells have sounded on the tiny Indian Ocean island of Mauritius, where injected drug use accounted for 90 percent of new infections in 2005, and HIV-prevalence figures have increased to 1.8 percent, from a previous low of less than 1 percent.

In Kenya almost 40 percent of drug users reported sharing needles, and 3 in 10 IDUs tested for HIV in a small cohort in the coastal town of Mombasa were HIV-positive.

Injecting drug use in South Africa is low compared to many other countries, but the consumption of drugs that are strongly associated with an increased likelihood of engaging in unprotected sex is on the rise, and reaching a much wider audience than previously. Experts agree that risky sex while under the influence of drugs is the country's most significant drug-related HIV risk.

Health officials in Tanzania are worried about rising HIV-prevalence levels among IDUs, who often use a dangerous cash-saving technique known as "flash blood", in which a user injects heroin or another illegal drug, and then draws a syringe full of blood for a second user to inject.

Struggling to respond

Mauritius, Kenya and Tanzania are among the countries that have recognised the need for HIV prevention among drug users in their national strategic plans, but other countries have yet to do this.

In Nigeria - an emerging market for drug consumption and a key trafficking transit point - there is a "general lack of awareness among policymakers and health practitioners of the emerging drug use and HIV among drug users", researchers noted in a 2006 report on HIV and drug use in the West African country.

Mauritius recently set up pilot needle-exchange programmes and methadone-maintenance programmes, but other affected countries have been slow off the mark.

Dr. Fayzal Sulliman, head of the only centre offering methadone treatment in Mauritius, admitted that cash-strapped countries in the region would find such measures expensive and difficult to implement, as they required additional infrastructure and resources. "But, in the long run, it will be less expensive when you think of the impact [of drugs] on crime and AIDS."

He warned that "This is the time to set up harm-reduction measures in Africa; if we don't do it now, it will be a bush fire."

See new indepth: Deadly cocktail: HIV and drug use