Mathematical processes can help to assess who might have infected whom with HIV. The more similar the genetic sequences in two samples are, the more likely it is that the two people infected each other. These kinds of analyses soon became part of legal proceedings relating to individuals who were accused of deliberately infecting other people with HIV
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.
One well-known and tragic case involved five nurses from Bulgaria and a doctor from Palestine, who were sentenced to death in Libya after allegedly infecting hundreds of children with HIV on purpose. However, analysis of the genetic material showed that the children had become infected with HIV long before the nurses arrived
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and the medical professionals were freed in 2007.
Tracking down a pathogen’s transmission paths
In recent years, analysis techniques have become considerably more sophisticated. Revolutionary technologies can determine the genetic sequences of a huge number of samples quickly and cheaply. For instance, MinION sequencing technology is small enough to sit in the palm of one’s hand. This means that in the event of an epidemic it can be used to sequence a pathogen’s DNA on site in a developing country . This avoids all the legal and logistical hurdles of exporting blood samples across national borders.
Mathematical and statistical methods, too, are constantly becoming faster and more reliable. This is the area my group is active in. We are working with other scientists to further develop the BEAST software package to analyze and interpret sequencing data. We are also committed to familiarizing the scientific community with the software. To this end, we initiated an annual series of international workshops
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to teach people how to use it.
Thanks to the progress we’ve made, we can now consider not only individual potential paths for the transmission of a given pathogen – as is common in legal proceedings – but also a pathogen’s paths through an entire population. With appropriate analyses and simulations, it is also possible to judge the effect of health policy measures such as border closures or flight bans.
Requirements for real-time analysis
While both MinION technology and BEAST software were employed during the West African Ebola epidemic of 2013–2016
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and the latest Zika epidemic in South America
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, cooperation did not run smoothly among the various parties involved and processes had not yet become fully established. That explains why the analyses took time to carry out.
