SHM data in research
Could you tell us a bit about the background to your research, including the issues surrounding HIV infection among MSM?
Although antiretroviral therapy is not a cure for HIV, it does decrease the viral population to very low levels. With very few viral particles, infected individuals are also far less infectious. It is therefore surprising that, despite high ART coverage in many countries, the number of new diagnoses amongst MSM has not declined. Moreover, in the Netherlands, MSM test more frequently and enter care earlier than heterosexual men, indicating equivalent access to, as well as higher levels of engagement with, HIV prevention and care services. The question therefore is where the new infections among MSM are coming from.
Several international follow-up studies of uninfected MSM who subsequently become infected, such as the Amsterdam Cohort Studies, suggest that the single most likely explanation for the resurgent epidemic among MSM since the roll-out of ART is increased sexual risk behaviour. This is despite several newly introduced prevention measures during this period, including free condom provision, motivational interviewing, counseling, free and anonymous STI and HIV screening. Therefore, innovative, further prevention strategies are clearly needed to lead to a substantial reduction in new infections.
What were the main findings of your paper?
Using the relationship between the genetic sequences of HIV viruses collected from patients as a marker for who could have likely infected whom, we were able to characterize around 600 past HIV transmission events that occurred among MSM in the Netherlands. Evaluating these events, we found that very few transmissions were attributable to men who had started ART or who had been lost to follow up. Rather, almost half of all transmissions were attributable to men who themselves had recently become infected (within 12 months or less). These transmissions are particularly challenging to prevent and imply that prevention services to uninfected MSM must be strengthened.
To look at which measures would have been most effective in preventing these past events, we conducted hypothetical microsimulations on the past events. We found that increased annual testing and the use of antiretrovirals by uninfected MSM as pre-exposure prophylaxis (PrEP) before sex could play a key role in bringing about a decisive decline in the HIV epidemic among MSM in the Netherlands.
What is the added value of SHM’s data?
By exploiting the genetic code of the virus, we can now quantify the sources of HIV transmission. At the heart of this emerging approach lies the integration with other types of data, from demographic individual-level data to a multitude of laboratory and clinical tests. This combination of data, all of which are routinely collected by SHM, enables the epidemiological interpretation of past, reconstructed transmission events. International consortia, such as the Phylogenetics and Networks for Generalised HIV Epidemics in Africa (PANGEA-HIV) through which I am currently funded, are now aiming to capitalise on this technology, using evidence from viral phylogenetic analyses to identify effective HIV prevention strategies.
Moreover, in an international context, the proportion of infected men and women in the Netherlands for whom a viral sequence is available is high. What's more, the ATHENA cohort provides comprehensive demographic and clinical data on almost all HIV-positive men and women, with the exception of the 1.5% who opt out. Taken together, these anonymised data provided by SHM represent a highly valuable resource for informing future HIV prevention strategies worldwide. Expanding the sequence collection further would allow more refined analyses, such as an analysis of prevention strategies that target subgroups of MSM or migrants.
I would like to end by thanking all patients at the HIV treatment centres in the Netherlands for their participation and all contributors to the ATHENA cohort for their efforts that made this study possible.