Phylodynamics of HIV-1 unique recombinant forms in China-Myanmar border: implication for HIV-1 transmission to Myanmar from Dehong, China.

China-Myanmar border plays a crucial role in HIV-1 transmission in Asia. Here, we performed Bayesian phylodynamics analyses on p17 gene using BEAST to investigate HIV-1 transmission in this region. Maximum clade credibility trees of subtype C and CRF01_AE show that majority of unique recombinant forms (URFs) and pure subtype strains from Dehong and Myanmar cluster together, forming large clades with ancestral geographical states of Dehong. Bayes factor tests support the statistically significant geographic diffusion link between Dehong and Myanmar. The estimated time to the most recent common ancestor of Myanmar URFs_BC (1999.2) was later than that of Dehong URFs_BC (1998.0), but earlier than that of Myanmar URFs_01BC (2004.3). Since 1998, HIV-1 recombination between subtypes B, C and CRF01_AE has been continuously occurring in China-Myanmar border region. These results suggest that HIV-1 subtypes B, C and CRF01_AE were most likely transmitted from Dehong to Myanmar, and predict that URFs_01BC should be also prevalent in Dehong, Yunnan.