Burmese injecting drug users in Yunnan play a pivotal role in the cross-border transmission of HIV-1 in the China-Myanmar border region

Abstract

Injecting drug users (IDUs) are the major risk group for HIV-1 infection in the China-Myanmar border area. There are a large number of Burmese IDUs living in Yunnan (Yunnan-mIDUs) who might be associated with the cross-border transmission of HIV-1. From 2010 to 2013, 617 Yunnan-mIDUs were recruited from three counties of Yunnan, 19.0% of whom were detected to be HIV-1 positive by serological testing. Partial HIV-1 p17, pol, vif-env, and env genes were amplified from the positive samples and were sequenced. Phylogenetic and HIV-1 subtyping analyses revealed that HIV-1 recombinant forms (RFs), including RF_BC (36.4%), RF_01BC (26.1%), RF_01C (9.1%) and RF_01B (1.1%), were predominant among this cohort. Of the identified HIV-1 strains, 14.8%, 9.1% and 3.4% belonged to subtype C, CRF01_AE and subtype B, respectively. Transmission cluster analysis showed that sequences from the Yunnan-mIDUs formed transmission clusters not only with those from Burmese IDUs but also with those from Chinese IDUs, indicating that Yunnan-mIDUs might acquire HIV-1 infection from or spread HIV-1 to both Burmese and Chinese IDUs. Phylogeographic analyses revealed three cross-border transmission patterns associated with Yunnan-mIDUs, in which Yunnan-mIDUs served as the crucial nodes linking the Burmese and Chinese IDUs. These results suggest that Yunnan-mIDUs are a potential viral reservoir for the diffusion of HIV-1 in Yunnan and play a pivotal role in the bidirectional cross-border transmission of HIV-1 in the China-Myanmar border region. More intervention efforts that focus on Yunnan-mIDUs are recommended in Yunnan's campaign against HIV/AIDS.

Keywords: China; HIV-1; IDUs; cross-border; Myanmar; transmission; epidemiology.

Figure 1.

The geographic location of the China-Myanmar border region and sample sites. The black line with a blue shadow shows the border between China and Myanmar; the red and black spots indicate sample sites in China and their border regions in Myanmar, respectively; and the yellow triangle indicates the well-known illegal drug production region called the “Golden Triangle.”.

Figure 2.

Maximum likelihood trees and cluster analysis results for the HIV-1 p17, pol, vif-env and env fragments sampled from Burmese injecting drug users in Yunnan, China. The sectors with different colors indicate different subtypes/recombinant forms of HIV-1; the blue triangles, red spots and purple squares indicate the sequences that were sampled in Longchuan, Yingjiang and Ruili Counties of Dehong Prefecture among Burmese injecting drug users, respectively; the black rhombuses indicate the sequences that were sampled in Longchuan and Ruili Counties of Dehong Prefecture among Chinese injecting drug users; and the brackets with numbers indicate transmission clusters that were identified by Cluster Picker.

Figure 3.

The maximum clade credibility tree based on the subtype C and CRF01_AE sequences of the HIV-1 p17 fragment in the China-Myanmar border region. The different colored lines indicate the HIV-1 strains from different geographical locations, and the black spots indicate the nodes of HIV-1 lineages. The state posterior probabilities are indicated beside major nodes, and the ages of nodes A, B and C are shown with 95% confidence interval.

Figure 4.

Schematic diagram of HIV-1 transmission patterns and trends in the China-Myanmar border region. The different colored spots indicate the HIV-1 strains from different geographical locations; the arrows indicate the transmitted directions; and the numbers beside them show the routings (a) or sequences (b) of each transmission direction.