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article imageUnderstanding why some people spread more germs that others

By Tim Sandle     Apr 1, 2017 in Science
Atlanta - Looking at how diseases spread from animal to animal, researchers have gained a new understanding into why some individuals are greater ‘spreaders’ of disease within a community than others.
The research is based on a review of wild primate social networks and has looked at the spread of parasites. The information is, according to the researchers, applicable to human societies. The study has been carried out by Thomas Gillespie, who is a professor at Emory University.
The focus of the research is with safeguarding primate species, given that some 60 percent of the approximate 500 different species of primate face an extinction risk. This is due to habitat loss and hunting (direct human activities), and also to disease. With disease, this is a combination of the disease itself and a consequence of the environmental impact from human activity.
The transmission of parasites between primates also has implications for people, given that some diseases can be passed between primates and people. Examples of zoonotic infections include HIV, Ebola, yellow fever and respiratory viruses. To add to this, the first recorded cases of Zika virus were with monkeys in 1947 in Uganda.
One limitation with mapping disease transmission is the assumption that any person in a given population has the same chance of passing on or contracting an infection. Professor Gillespie’s research suggests we need a more sophisticated model and that the ‘equal chance’ assumption isn’t often borne out in reality. Instead, the researcher argues, we should focus on the 80: 20 rule. In this case, 80 percent of disease transmission events in an epidemic are caused by 20 percent of individuals. Key to unraveling is this is with understanding why some individuals are so-termed ‘super-spreaders’.
Professor Gillespie thinks that studying primate social networks will reveal information, for both primates and people, more quickly. This is due to the similarity in social networks and because of the many recorded, historical studies available. The research to date has helped to pick out some of the high-risk traits and identify super-spreaders in a relatively predictable way.
The usefulness of the research could, for instance, help to select which people should be given a vaccine first should a disease outbreak occur (types of targeted interventions). Such research can also help to develop models based on environment and behavior.
Summing up the study, Professor Gillespie said: “We hope it helps jump-start a new way of approaching research into disease transmission -- one that integrates ecology, behavior and evolution on a grand scale."
The research has been published in the journal Trends in Parasitology, under the heading “Making New Connections: Insights from Primate–Parasite Networks.”
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