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NEW DELHI, May 2: The dengue virus evolved "dramatically" over the last few decades in India, according to a study led by scientists at the Indian Institute of Science (IISc), which stresses the need for developing a vaccine against the strains found in the country.
Dengue cases have steadily increased in the last 50 years, predominantly in the South-East Asian counties. However, there are no approved vaccines against the mosquito-borne viral disease in India, although some vaccines have been developed in other countries.
"We were trying to understand how different the Indian variants are, and we found that they are very different from the original strains used to develop the vaccines," said Rahul Roy, Associate Professor at the Department of Chemical Engineering at IISc Bengaluru.
The study, published in the journal PLOS Pathogens, examined all available (408) genetic sequences of Indian dengue strains from infected patients collected between the years 1956 and 2018 by others as well as the team themselves.
There are four broad categories-serotypes-of the dengue virus (Dengue 1, 2, 3 and 4).
Using computational analysis, the team examined how much each of these serotypes deviated from their ancestral sequence, from each other, and from other global sequences.
"We found that the sequences are changing in a very complex fashion," said Roy, corresponding author of the study.
Until 2012, the dominant strains in India were Dengue 1 and 3, the researchers said.
However, in recent years, Dengue 2 has become more dominant across the country, while Dengue 4-once considered the least infectious-is now making a niche for itself in South India, they found.
The team investigated what factors decide which strain is the dominant one at any given time.
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