A new dengue virus has been confirmed for the first time in the country. Scientists at Pune-based National Institute of Virology (NIV), who spotted it and had been tracking it.
They said the new virus of an Asian genotype (genetic structure) was a concern as it was associated with severe and extensive epidemics in Singapore in 2005 and Sri Lanka in 2009.
The virus type was also responsible for outbreaks in Tamil Nadu in 2012 and Kerala in 2013, the scientists said.
The findings were published in a research paper, ‘Emergence of the Asian genotype of DENV-1 in South India’, in the peer-reviewed journal “Virology” this month.
There are four distinct types circulating in India — dengue virus type 1 (DENV-1), DENV-2, DENV-3 and DENV-4. The Asian genotype of DENV-1 was found in virus isolates drawn from blood samples of dengue-infected patients in southern India.
The finding does not mean the Asian genotype has become more prevelant than the American-African genotype of DENV-1 that has been in circulation in India since the 1940s. Scientists said both types of DENV-1 were still cocirculating in TN and Kerala.
Experts are studying samples from Maharashtra, Delhi and some other states to find out whether the Asian genotype of DENV-1 was present in these regions.
“The Asian genotype was responsible for epidemics in Singapore during 2005 and in Sri Lanka during 2009. This genotype was not found earlier in India. It is a new entrant to India,” senior scientist Devendra Mourya, director of NIV, told.
DENV-1 was the predominant virus in the 2012 outbreak in TN. “All the dengue virus 1 that were genetically studied or sequenced by NIV scientists belonged to the Asian genotype. However, we have not tested all the samples so we cannot say that the Asian genotype has completely replaced the earlier genotype of dengue virus 1,” Mourya said.
The Asian genotype was seen only in TN and Kerala.
“We studied the genetic makeup of the virus in Maharashtra and Delhi during the same period. We did not observe any change in the genotypes of the four dengue virus types.
Continuous monitoring of the viruses’ genetic structure may provide a warning system to forecast outbreaks,” said NIV scientist K Alagarasu, among those involved in the study of the Asian genotype.
The new virus type is still in circulation. “The relevance of the currently circulating Asian genotype needs further investigation,” Alagarasu added.
A large number of samples should be tested before one can say that the new Asian genotype has become dominant over the African-American genotype in India.