Deadly dengue strains in Delhi this season

September, 2015

New Delhi: A preliminary test report by AIIMS suggests two of the most virulent strains of dengue-type II and type IV-are circulating in Delhi this year.

"Our report is based on preliminary data from the first lot of nine acute-phase serum samples (collected within 10 days of disease onset) of suspected cases," said an official of microbiology department, AIIMS. 

AIIMS' virology laboratory of the microbiology department, which is an apex laboratory of the National Vector Borne Disease Control Programme for dengue and chikungunya, isolated dengue viruses from six out of nine samples, and identified type II virus in four samples and type IV in two other samples. 

Dengue strains are of four types. Type I causes classic dengue fever, type II leads to haemorrhagic fever with shock, dengue III causes fever without shock and dengue IV causes fever without shock or profound shock. 

"Type II and IV are the most virulent forms of dengue. We have not seen so many critically-ill patients though. It may be because previous exposure to the viruses has lessened its impact," said Dr Navin Dang, Consultant microbiologist and Director of Dang's Laboratory in South Delhi. 

Dr Ekta Gupta, Associate Professor at ILBS, said a larger study may be required to find out the predominant strain. "In the past few years, research shows, multiple strains of the dengue virus are present in a community," she said.

This year Delhi has reported more than 830 dengue cases so far and two deaths have been reported. On Friday, some of the AIIMS staff held protests on the campus over the death of a child due to the disease. 

Experts said dengue, which assumed an epidemic form in 1996, followed by outbreaks in 2003, 2005 and 2006 in the capital, has become hyper-endemic-a disease that is constantly present at a high incidence and/or prevalence rate and affects all age-groups equally. "It could be due to the rapidly growing population, increasing urbanization and lack of an effective vaccine and vector control programmes," said an expert.