A strain of dengue not known to be common a decade ago is behind the most severe cases of illness in Telangana, revealed researchers from University of Hyderabad, who sequenced the virus’s genome.
Dengue 4 (or DENV 4) is one of the four known serotypes (a sub-species structural classification based on how the virus causes infection) that for long has been in the shadow of DENV 1 and DENV 2, common strains associated with milder variants of illness. In recent years, outbreaks in Pakistan, India and other South East Asian countries have led to finding of varying strains of the virus. Consequently, M. Venkataramana of the UoH and his team set about studying the virus that caused outbreaks in 2014 and 2015 in Telangana. They identified DENV 4 in severe cases of illness.
“DENV 4 infections tend to be severe and are associated with dengue shock syndrome,” Dr. Venkataramana, an Assistant Professor at UoH’s Department of Biotechnology and Bioinformatics, said. “To our concern, we have seen primary infections causing severe illness and death.”
First-time infections
Primary infections or first-time infections were earlier considered relatively mild. Secondary infections were often noted to be serious, particularly when the virus was of a serotype different from the virus that caused the first infection. For their study, researchers collected blood samples from patients treated in Hyderabad for dengue and identified the serotype of viruses. In 2014, when they had finished serotype identification in 33 samples, the researchers found DENV 4 in 11 samples. Four of these samples revealed first-time infections while seven were co-infections with other serotypes. The study has been published in the journal Epidemiology and Infection .
Consequently, researchers sequenced the genome of DENV 4 from a blood sample of an eight-month-old infant diagnosed with dengue shock syndrome in 2015. Gene sequencing revealed the strain was different from earlier reported DENV 4 strains. While the infant survived the infection after intensive care and ventilator treatment, the researchers note that DENV4 infections carry high mortality risk.
Dr. Venkataramana said their analysis of the sequenced genome also showed Hyderabad underwent changes that would help it evade immune response developed in the body following a previous dengue infection. According to the Ministry of Health, in 2015 dengue infected 1,831 people and killed two in Telangana. Last year, 2,764 infections and four deaths were officially reported from the State. The data mainly restricts itself to public healthcare institutions though private health institutions too are mandated to notify dengue infections and deaths.
The researchers hope their study would convey the importance of controlling Aedes mosquitoes, which pass on the virus to humans, given that there are no specific treatments or vaccines for dengue available.
Published - March 04, 2017 10:55 pm IST
