HIV Transmission Source and Route Evaluated Through a New Intervention Method

HIV Transmission Source and Route Evaluated Through a New Intervention Method

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Highlights:
  • A new method developed to determine the effectiveness of an intervention found that the intervention decreased HIV disease transmission
  • The technique involves studying how HIV pathogens have evolved and how they get transmitted in a community
An international team of researchers has developed a new method to determine how effectively interventions curb the spread of infectious diseases like HIV.
HIV Transmission Source and Route Evaluated Through a New Intervention Method

The researchers include several people from the Center for Drug Use and HIV/HCV Research (CDUHR) at New York University. The study has been published in the American Journal of Epidemiology.

The method involved using genetic sequencing to understand the evolutionary relationships among the pathogens, in this case, viruses, and established the source of disease and whether its transmission in the community can be traced back to individuals who may have been or may not have been a part of an intervention.

Although we have gained considerable knowledge in the last decade, on how pathogens spread, we are still challenged in preventing the transmission of infectious diseases. Pathogens find it easier to travel from one person to another nowadays, due to the increase in international commuting and increase in densely populated areas. Controlling infectious diseases has become an immediate public health priority.

Scientists and public health practitioners find it difficult to evaluate the effectiveness of an intervention - in other words, whether an intervention is effective in reducing the transmission of disease in a community. Examples of interventions are needle exchange programs or treatments with antiretroviral therapy.

Most of the interventions measure their effects only on the people participating in the study but fail to consider the community effect, or how an intervention can minimize the spread of disease from people or the source directly involved, to other community members.

"Our research seeks to understand if an intervention has a community effect and can reduce disease transmission not only by the recruited individuals, but also by the contacts in their risk networks," said Samuel R. Friedman, director of the Institute for Infectious Disease Research at National Development Research Institutes (NDRI), associate core director and senior theoretician at CDUHR, and the study's senior author.

What is Phylogenetics?

Phylogenetics is the study of evolutionary relationships among different kinds of biological entities - mostly species, individuals or genes.

A person studying the subject will ask and answer the following questions:

What are the evolutionary relationships among biological entities - mostly species/individuals/genes of interest?

How do genes, genomes, species and molecular sequences evolve? How they came to be the way they are today.

What are the general principles that will help us predict how they will change in the future?

Can this course of sequence evolution be described better with a mathematical model?

All these can be represented using a phylogenetic tree that can be constructed using the molecular sequences and combine this with our understanding of sequence evolution, which is described using an evolutionary model.

The tree enables us to infer evolutionary events that happened in the past, gives us more information about the evolutionary processes operating on sequences, helps us understand how evolution works and develop better mathematical models of development.

Novel method to Evaluate an Intervention - Measuring Community Effect

The research team developed a new approach involving phylogenetics to evaluate an intervention for reducing HIV transmission.

They used phylogenetics or the evolutionary relationships or histories among organisms to comprehend the evolutionary dynamics of HIV. This will help them examine the transmission of the virus from already-infected people to those newly infected.

The procedure involved collecting blood samples from three groups of people:
  • Individuals with HIV who participated in an intervention study
  • Individuals with HIV who are not part of the intervention (the control group)
  • Individuals who are newly infected with HIV (formed at a later date).
They performed genetic sequencing of HIV to compare characteristics of the virus to determine the source of transmission and whether new infections can be linked to individuals who did or did not participate in the intervention.

Traditional methods are unable to trace infections back to a source - hence we have never known how effectively we can reduce the spread of HIV within a community.

The researchers simulated an intervention to prevent HIV transmission among people who inject drugs.

They compared transmission from those with HIV who did or did not participate in the intervention.
  • Fewer people contracted HIV from individuals in the intervention - leading to the conclusion that the simulated intervention reduces disease transmission.
This method can assess the broader community effect of an intervention without having to follow up with study participants. It only requires a one-time collection of blood samples. Sometimes it gets difficult to track participants long-term, especially in communities for which follow-up is a challenge, such as people who inject drugs. This method can circumvent that problem.

The method has an added advantage that it can be used for other infectious diseases beyond HIV.

References:
  1. New method helps determine effectiveness of interventions in reducing spread of HIV - (https://www.eurekalert.org/emb_releases/2018-08/nyu-nmh073018.php)
  2. Gkikas Magiorkinis, TimokratisKaramitros, Tetyana I Vasylyeva, Leslie D Williams, Jean L Mbisa, Angelos Hatzakis, Dimitrios Paraskevis, Samuel R Friedman. Aninnovative study design to assess the community effect of interventions to mitigate HIV epidemics using transmission-chainphylodynamics. American Journal of Epidemiology, 2018; DOI: 10.1093/aje/kwy160


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