In tracing the origins of a tuberculosis outbreak in a B.C. community to crack cocaine use, a team of researchers have pioneered a new method using DNA gene sequencing combined with social networking surveys.
Using gene sequencing to investigate a bacterial outbreak, which hadn’t been done before, helped the researchers gain insight into the reasons behind the TB outbreak that affected 41 people in Port Alberni on Vancouver Island.
A rise in crack cocaine use within the community may have been the trigger for the outbreak, the researchers found.
Genome sequencing was used to identify subtle differences in the bacteria, which made it traceable to distinct clusters of people. Social network surveys were then used to track areas frequented by those infected, showing how contact between people linked to areas of transmission.
The novel approach was able to trace outbreaks to poorly ventilated areas such as crack houses and other squalid environments. The bacteria were spread by coughing, which transmitted the disease from person to person.
The researchers were also able to identify several infected “super spreaders”—individuals who were giving the disease to many others, thereby helping contain the spread of the disease.
The research, conducted by scientists from Simon Fraser University and the BC Centre for Disease Control (BCCDC), is attracting international attention after being published in the prestigious New England Journal of Medicine on Feb. 24.
Fiona Brinkman, head of the SFU research team and associate professor in the Department of Molecular Biology and Biochemistry, says the unique research method allowed them to gain detailed insight into the outbreak that wasn’t previously possible.
“Some outbreaks of disease will occur and you’re really not sure why it’s occurring. But with the more detailed analysis, we were actually able to determine it was likely the crack cocaine use in the area that was leading to a higher susceptibility to transmitting TB.”
Using social networking surveys overcame the difficulty of tracking people who might not have a stable dwelling or are reluctant to identify other members of their network due to involvement in illegal activities, Brinkman says. By discovering which areas infected individuals frequented, researchers could get a more accurate view of trends in the spread of disease.
Brinkman hopes the new method will be helpful in other disease outbreaks, and as the approach is refined be able to find answers faster, leading to better control measures.
“Ideally within the first couple of weeks of the outbreak happening we want to get this data and be able to see what’s going on right then.”
She says Canada has relatively low incidence of TB because of higher quality living conditions and a lower density population. But when a small geographic area becomes highly populated, there is an increased risk of disease outbreaks. During the Olympics for example, the BCCDC was on high alert.
In recent years, the worst TB outbreak in Canada occurred in Nunavut, which reported 100 new and active cases in 2010. This was the highest number in the territory’s 10-year history, and 62 times the national average.
The World Health Organization estimates one third of the world’s population is infected with TB bacterium, but only 5-10 percent of those who carry the virus will get sick in their lifetime. An estimated two million people die from TB every year, mostly in developing countries.
After its peak in the 19th century, tuberculosis was on a global downward trend until 1986, when it re-emerged as a public health threat. A major factor in its comeback is thought to be the increase in HIV, which lowered immunity to the bacterium that causes TB. Other causes are overcrowding, mobile rural-to-urban populations, drug resistant strains, poverty, and lack of public health infrastructure.
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