Earlier this month, UNAIDS published its annual Gap report, drawing together global data on HIV/AIDS alongside information and analysis about the 'people being left behind' in the fight against the disease.
Among the 12 groups it identifies as being most at risk of HIV transmission and facing barriers to treatment are international and internal migrants. The report outlines some of the factors that contribute to this heightened vulnerability, flagging up "limited access to health information and services" as a key one.
Prabodh Devkota is senior regional project director of humanitarian charity CARE International's EMPHASIS (Enhancing Mobile Populations' Access to HIV and AIDS Services, Information and Support) project.
Headquartered in Nepal, EMPHASIS was set up in 2009 to address the HIV vulnerability of migrants moving between Bangladesh, Nepal and India. It has done this by testing innovations in delivering HIV services, and gathering data on their impact. 
Migrants all over the region are highly vulnerable to HIV and face numerous barriers to treatment, Devkota says, while "language barriers in destination countries and the fact that many of the migrants are not literate" makes access to services even more complicated.
But he explains that information-based interventions that provide migrants with clear information on HIV care options and policies in different countries can reduce migrant vulnerability.
For example, EMPHASIS has run outreach programmes and information centres for migrants and their families, and broadcast video programmes, radio shows, and audio messages on buses to provide even illiterate migrants with information about high-risk sexual behaviour and on healthcare options in different countries.
The project is the only one in South Asia to provide these services in each of the countries migrants transit through. This is unlike most other migrant health projects which tend to focus on either source or destination countries, says Devkota.
"Providing information on health facilities and their locations, and health processes and protocols is extremely useful for the migrants and vital to their safety," Devkota says.
Cross-border communication between families also underpins this work, he says.
The project has "made conscious efforts to boost communication between [the often male] migrant workers and their wives at home, using mobile phones and Skype, accessed from drop-in centres". This helps migrants feel less socially isolated, more informed about safe practices, and less likely to have unsafe sex, he says.
The project's research has shown that cross border interventions can be effective. For example, it has shown that Bangladeshi migrants who were involved in the EMPHASIS project were six times more likely to feel comfortable discussing HIV-related issues with their spouses than the control group. 
Cross-border dialogue with different actors - affected groups, health-workers, NGOs and governments - is also critical for opening up HIV treatment for mobile populations, Devkota says.
Through its NGO partnerships and negotiations with the Indian and Nepali governments, EMPHASIS has helped develop a cross-border referral system so that "any HIV-positive migrant from Nepal who's in possession of a referral document from the Nepali government can access free antiretroviral treatment in India," Devkota says. "This has been one of the significant achievements of the project," and provides valuable lessons for the broader HIV sector, he adds.
Imogen Mathers is writer/producer at SciDev.Net. @ImogenMathers
 The Gap report (UNAIDS, 16 July 2014)
 Prabodh Devkota and others An integrated approach to address mobile people's vulnerability to HIV and migration EMPHASIS experiences in a nutshell (Care International; Overseas Development Institute, July 2014)
 Fiona Samuels and others The effects of an HIV and AIDS project on migrants at source and destination sites in Nepal, Bangladesh and India: findings from a quasi-experimental study (Care International; Overseas Development Institute, July 2014)