History of subtype C: Epidemiology

The epidemic spread of HIV in sub-Saharan Africa began in the late 1970s and, during the late 1980s, gradually spread to the South of the continent. HIV-1 subtype C was first discovered in North East Africa in the early 1980s (1,2) and has since also moved to the southern parts of Africa. In addition, the subtype C epidemic has also spread to East and Central Africa where it is becoming the predominant subtype (3, 4, 5). The C epidemic has also spread to South and Central China, India and Brazil (6, 7, 8). The variants circulating in China are mainly B/C recombinants where the subtype C component appears to have been introduced into China from India (6).

The subtype C epidemic has now become the most predominant subtype in Southern African countries where HIV prevalence is the highest in the world. Extrapolating the subtype C sequence frequency from the Los Alamos sequence database shows that subtype C accounts for >46% of all infections in sub-Saharan Africa and contributes to just over 42% of global infections. Of all the new infections that occurred globally during the period from 1999 to 2002, 45% are estimated to be subtype C infections, based on the subtype C sequence frequency obtained from published data.  It is important to note that this estimate could be greater than the actual prevalence as a result of sequencing bias. However, there is still much evidence suggesting that subtype C is increasing and that there is a definite need to monitor and describe the viruses circulating in countries with high subtype C infections.

References: