A team of scientists has sequenced the genome of Ebola virus strains circulating in Guinea to trace the spread of the disease and monitor its progress. Their findings, published Wednesday in the journal Nature, have revealed three distinct variants of the virus that are co-circulating in the West African country, especially in its urban regions and neighboring towns.

The Ebola epidemic spread rapidly through West Africa and has been ongoing for over a year, with over 27,000 reported cases and 11,000 deaths. The source of the outbreak has been traced to a wooded area of southeast Guinea, from where it rapidly spread to the capital, Conakry, and then to neighboring countries like Sierra Leone and Liberia.

A team of scientists from the Institut Pasteur in Senegal and in Paris, the University of Sydney and the French National Center for Scientific Research analyzed the Ebola virus variants that circulated in Guinea between July and November 2014.

Analyzing the samples led to the discovery that the three distinct variants of the disease were co-circulating in Guinea. The first is closely related to variants of the viruses found near the start of the epidemic in March 2014, and is found only in Guinea. The second variant is more closely related to the types of virus circulating in Sierra Leone, but it could also represent a parallel evolution in the two strains, the researchers said in the study. The genetic sequences represent the missing link that led to two separate strains of Ebola being introduced to Mali, in October and November 2014, the study found.

The final variant was identified in Conakry and its surrounding towns. It bore marked similarities to variants found in Sierra Leone, which, combined with epidemiological information, give evidence of Ebola being reintroduced from Sierra Leone to the Conakry region multiple times.

While the study highlighted the disease’s variations and the speed of its spread from Guinea, it also found that its rate of mutation was well within expected levels, easing fears that the disease could adapt faster than doctors and scientists could find a cure for it or even mutate to become airborne.

Ebola infections have spiked in Guinea and Sierra Leone for two weeks in a row, with health officials reporting 16 new cases in Guinea and 15 new ones in Sierra Leone last week. But officials say they’re optimistic about defeating the epidemic. The bordering country of Liberia was declared Ebola-free in May.