  Background: Approximately 40% of adults in Botswana are HIV-infected. The
Botswana antiretroviral program began in 2002 and currently treats 34,000
patients with a goal of treating 85,000 patients (~30% of HIV-infected adults)
by 2009. We predict the evolution of drug-resistant strains of HIV that may
emerge as a consequence of this treatment program. We discuss the implications
of our results for the World Health Organization's (WHO's) proposed
surveillance system for detecting drug-resistant strains of HIV in Africa.
Methods: We use a mathematical model of the emergence of drug resistance. We
incorporate demographic and treatment data to make specific predictions as to
when the WHO surveillance threshold is likely to be exceeded. Results: Our
results show - even if rates of acquired resistance are high, but the
drug-resistant strains that evolve are only half as transmissible as wild-type
strains - that transmission of drug-resistant strains will remain low (< 5% by
2009) and are unlikely to exceed the WHO's surveillance threshold. However,our
results show that transmission of drug-resistant strains in Botswana could
increase to ~15% by 2009 if resistant strains are as transmissible as wild-type
strains. Conclusion: The WHO's surveillance system is designed to detect
transmitted resistance that exceeds a threshold level of 5%. Whether this
system will detect drug-resistant strains in Botswana by 2009 will depend upon
the transmissibility of the strains that emerge. Our results imply that it
could be many years before the WHO detects transmitted resistance in other
sub-Saharan African countries with less ambitious treatment programs than
Botswana.
