Mosquitoes mutate to carry ‘dangerous’ virus

Instead of the commonly found Type-3 strain of the dengue virus, this time there has been an increase in the number of patients affected by the Type-1 and Type-4 of the virus in Kolkata and its adjoining districts. According to the virologists and doctors, the increase in Type-1 and Type-4 cases indicate that both Aedes Aegypti and Aedes Albopicktus — the vectors of the disease — have mutated.

"Earlier, the dengue symptoms used to be high fever, coupled with rash , body ache and nausea. Now, the symptoms are different, which includes pain in lower abdomen, diarrhoea," said Dr Bibhuti Saha, a virologist associated with School of Tropical Medicine.

According to him, this time dengue is affecting major organs of the body like liver, pancreas, and kidney. "Mutation (of vectors) is responsible for this two strains of dengue virus becoming more strong," he added.

A study by the National Institute for Cholera and Enteric Diseases (NICED) also confirmed the same. The study found that of every 1,000 residents of the city, who were infected over the past one month, as many as 23 were affected by either Type-1 or Type-4. "This is a very high rate of prevalence, comparable to other hyper endemic countries like Thailand, Columbia, Nicaragua and some other Latin American locations," said a scientist at the institute.

The NICED study, which surveyed 30,000 people with high fever across the city, also found a distinct change in the pattern of infection this year. But they are yet to confirm whether any new sub type of dengue virus has also come up. "Last year, we had detected only Type-2 and Type-3 virus, but this time, Type-1 and Type-4 have also been found. This is the first instance of these two strains triggering a dengue outbreak in the city in recent years," said Sekhar Chakraborty, Director of NICED.

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