Epidemiological dynamics of a 25 years outbreak in Gran Canaria inferred from whole genome sequencing

Abstract

Pág. 26-27 del libro de abstracts que se adjunta. Tuberculosis is an air spreading infectious disease and is still one of the ten top causes of death worldwide. Halting TB transmission is central to control and reduce disease incidence. Thus special attention should be paid to massive and uncontrolled transmission as occurs in outbreaks. In 1993 a Liberian refugee introduced a Beijing strain to Gran Canaria, it spread quickly and was reported as outbreak in 2001. In the following years the same strain were registered in other islands from the archipelago and also in the peninsula (2002). We applied whole genome sequencing and phylodynamic bayesian analysis to characterize the historical roots and the epidemiological patterns of this outbreak. We selected a total of 66 cases between 1993-2018 including one case from Switzerland obtained from public databases. In addition, we compared the strain against a database of 36000 genomes from global sources. The outbreak strain belongs to L2.2.3; as expected it has a phylogeographic relationship to West Africa but also to Vietnam. Our analysis revealed that the index case remained infectious over several months causing a secondary outbreak. The phylodynamics results revealed periods of expansion meaning that the outbreak is still uncontrolled. As conclusion, poor treatment adherence of the index case caused an outbreak that spread rapidly in The Canary Islands subsequently reached the continent to later become an ongoing international outbreak.