Genome-Mapping Research Yields Surprising Results on Tuberculosis

Infectious disease may lie dormant for years.

Think having a cold for a week is bad? According to the results of a recently published study, humanity has been dealing with tuberculosis (TB) for up to 70,000 years.

Tuberculosis is a bacterial infection, an infectious disease which primarily affects the lungs. It kills 1.4 million people around the world annually.

In the study published online by Nature Genetics on September 1st, researchers examined the genomes for 259 different strains of the pathogen and used the resulting data to explore the global diversity of the virus and to reconstruct its evolutionary history.

Previously, the scientific community had accepted that the disease transferred to humans from livestock roughly 10,000 years ago during the rise of agriculture. However, the recent study found evidence that TB has its origins in hunter-gatherer tribes in Africa nearly 70,000 years ago. According to the study, early humans carried the disease with them as they migrated out into other areas of the world and, consequently, the disease expanded into the human population.

One of the major roadblocks to dealing with TB today lies in its adaptability: the bacteria have the ability to evolve and become resistant to antibiotics. In these cases, treatment can last from 6 months to over eighteen months with potentially skyrocketing costs to patients.

Another of the disease’s adaptations has proven to be a key finding of the study. Lead researcher Inaka Comas told the BBC in an interview that TB bacteria can deactivate and sit dormant inside a person during times when human population density is low and then reactivate when there are more potential hosts to move to. It is this adaptation, the researchers say, which allowed TB to survive during the early years of human civilization.

The global fight against TB has made major leaps since the disease was targeted by the United Nations’ Millennium Development Goals at the beginning of the decade. As of 2012, the World Health Organization (WHO) reported a 41 per cent decrease in new infections worldwide.

However, the WHO’s Global Tuberculosis Report released in 2012 points out critical funding gaps for research and development to the tune of US$1.4 million. The organization expressed concern at the time that the global momentum to eliminate the disease was fading.

Despite this, the recent study positions the scientific community to work toward further developments in understanding TB, according to Dr. Ruth McNerney, a lecturer in pathogen biology and diagnostics at the London School of Hygiene and Tropical Medicine.

“There are now thousands of TB genomes being sequenced in big databases so that in the next five years we’ll know more about TB than we ever have, which is exciting,” she states.

According to Comas, these findings are only the beginning.

“The next step in this research would be to use the genetic information to understand this activation and deactivation mechanism of TB.”

By Sarah Hartwick, Staff Writer

Sarah Hartwick is a freelance writer and an avid traveler. In her spare time, she works with Schools Building Schools, a growing NGO that’s striving to spread access to education throughout Sub-Saharan Africa. Check out her blog to follow her adventures around the globe.