Last month, South African Aids campaigners won a huge victory. Denying HIV drugs to positive mothers to prevent mother-to-child transmission (MTCT) was declared illegal. So, cause for celebration, yes?
Not if a Ugandan study of MTCT prevention, the HIVNET 012 trial, correctly predicts what may happen.
Why? Drug resistance.
South Africa's activists chose, understandably, to campaign for the cheapest-possible option. Two nevirapine pills. One to mum at the onset of labour, one to the newborn child. Cost to South Africa: £5.2m a year. The next-cheapest studied option, an AZT/3TC combo, would cost nearly £8 million.
Unfortunately, the cheapest may also be the worst option. Nevirapine is a perfectly good drug if it is used in combination with others. But HIV becomes resistant to it very easily. If nevirapine is given by itself, just one dose can make you virus-resistant.
This is what happened to one in five of the mums in the HIVNET trial. What are they supposed to do next time they conceive?
Worse, one in ten of the babies still became HIV positive - and nevirapine-resistant. That means, if nevirapine becomes available countrywide, that 6,000 babies a year born to positive mums in South Africa could end up drug-resistant.

Nevirapine resistance is bad news. It usually means resistance to all the current non-nucleoside class.
People resistant to 'non-nukes' have to rely on the often more toxic and certainly more expensive protease inhibitors. That means when cheap HIV drugs do come to South Africa there may be kids and mums dying of resistant superbug while others live on.
It's not too late to change the prescription. Other regimes against MTCT - including the AZT/3TC one - work just as well, and resistance develops much more slowly.
We have been here before. Ironically, AZT was the problem then. Remember when it was the only drug around? People were so desperate for any treatment then that campaigners like ACT-UP did 'die-ins' in the street to get it approved for use against Aids. So people started taking AZT - by itself. But AZT 'monotherapy' exacted a terrible price.
A recent study (also see p.35) has found widespread drug resistance and treatment failure in the USA. Two-thirds failing their HIV treatment. A quarter catching drug-resistant HIV.
As often as not, that 'one drug' is AZT. The people who died while taking AZT monotherapy left their resistant viruses behind them, like unquiet ghosts. They haunt the positive population still, denying many a chance of health.  

You can't just zap HIV. You have to outwit it tactically. Make the wrong move, it could checkmate you years down the line.   The positive people of South Africa have won a great battle. But they must demand options other than 'naked nevirapine' if they are not to lose a war.