May 24, 2011

Social Network Stopping Disease Outbreaks

(Ivanhoe Newswire) -- Combining new-fangled technology of whole genome sequencing of bacteria along with social networking analysis, public health officials are now able to get a far more comprehensive picture of disease outbreaks that will better aid in tracking in addition to hindering them before they get out of hand.

"Public health agencies are now able to harness the power of genome sequencing, which, when combined with the detailed clinical and epidemiological data we have access to, allows us to reconstruct outbreaks and really understand how a pathogen moves through a population," which Jennifer Gardy of the British Columbia Center for Disease Control, was quoted as saying.

An outbreak of tuberculosis occurred over a 3-year period in a medium-sized community in British Columbia.  In order to hinder the event, public health officials turned to conventional epidemiological methods to classify the source and other causative factors, however the results were unclear.

The researchers combined two new-fangled tools to get a more clear picture of the outbreak: social network analysis, which has become progressively more common in tracking contagious diseases in the past decade, and whole-genome sequencing (analysis of the entire microbe's DNA), which has become lower in cost and less time-consuming over the past few years.

"The complete genome sequence of a pathogen is the ultimate DNA fingerprint, and now, with the costs and time associated with genome sequencing dropping almost exponentially, it is possible to sequence most or all of the bacterial isolates taken from and outbreak," says Gardy

And while it may sound like something having to do with Facebook, social network analysis takes conventional epidemiology one step further, asking patients about more than just with whom they have been in contact.  In this case Gardy and her colleagues asked patients for a comprehensive account of their time on a daily basis including where they went and what they did at those places.

"Instead of getting a list of names, you are getting names, places and behaviors, and you can paint a much more detailed picture of the underlying structure.  Key people and places and certain behaviors that might be contributing to an outbreak's spread become much more apparent and allow you to adjust your outbreak investigation in real time as this new information becomes available," says Gardy.

Using this novel combinatorial technique, the researchers ultimately determined that the outbreak was probably not brought about by hereditary changes to the pathogen, but was instead likely due to increased usage of crack cocaine in the community.

Furthermore, they were able to establish that a few chief individuals acted as superspreaders, and these people were collectively well-connected and symptomatic for long periods of time.  This information is being used in an existing outbreak investigation where public health officials are trying to target socially admired people for screening as a priority.

"We took an outbreak that was an absolute mystery by traditional methods and solved it using genome sequencing and social network analysis," concludes Gardy, who calls this and other genomic epidemiological studies "a new and exciting direction for epidemiology and the study of infectious disease, particularly for public health agencies."

SOURCE: 111th General Meeting of the American Society for Microbiology, May 22, 2011