Date Published: January 30, 2015

Source:                 PLOS Biology

Authors:              Timo Ernst, Suzi McCarthy, Glenys Chidlow, Dagwin Luang-Suarkia, Edward C. Holmes, David W. Smith, Allison Imrie

Summary:           A study reveals the emergence of a new lineage of DENV (Dengue Virus) from returning travelers to Australia from Indonesia.

Dengue is the most rapidly spreading viral disease among humans. It’s endemic to most tropical and sub-tropical countries and causes an estimated 390 million infections to occur every year. Most of the disease burden is borne by people of Southeast Asia and the Western Pacific region. Understanding how the dengue moves from country to country and how it changes is vital to understand how to solve the problem. However, the data required to do such an analysis was lacking, thus limiting the attempts the scientists made to understand the hyperendemicity of the virus and its severity.

The authors of the study sequenced the E gene of DENV (Dengue Virus) that was isolated from travelers travelling to West Australia from 7 countries throughout Asia. The collected these samples and sequenced the genes over a span of two years from 2010-2012. The authors found that a majority of the virus originated in Indonesia which is a popular travel destination for Australians. They identified the hyperendemic transmission of all four DENV stereotypes in Indonesia in 2010. The Dengue is caused by infection with any one of these four stereotypes. The genotypes of these stereotypes can lead to lineages that either turnover, displace or introduce new lineages that can also cause dengue. The authors explained how it is important to track these changes and novel appearances since they are associated with a severe disease.

After having done the research, the authors found that a new lineage had emerged. This variation DENV2, or the cosmopolitan genotype, had appeared among travelers returning to Australia from other southeastern Asian countries. The introduction of this new genotype to the new populations of humans was caused by transmission. The new genotype was introduce due to mutations. The authors found that this new lineage originated in Bali in Indonesia. In the end, the authors discussed how due to a dearth of information regarding DENV from countries like Indonesia regarding sequenced genotypes, they weren’t able to determine when the new lineage emerged or whether it was present in another form in other countries before 2012. However, the concluded saying that surveilling returning travelers that are ill can help determine where the illness originate from.

This study shows a prime example of evolution happening on the smallest scales which have an astounding effect on a larger scale. The emergence of a new lineage of a certain virus through mutations shows the most basic form of evolution. This new lineage of DENV shows that it is being selected for among many possible mutated forms of DENV.

Citation:              Ernst T., S. McCarthy, G. Chidlow, D. Luang-Suarkia, E. C. Holmes, D. W. Smith, and A. Imrie. 2015. Emergence of a New Lineage of Dengue Virus Type 2 Identified in Travelers Entering Western Australia from Indonesia, 2010-2012. PLOS Neglected Tropical Diseases 9: e0003442.