DENV-2, the severest of all dengue virus types, is likely the key factor contributing to higher rates of dengue deaths and infections this year, says a government study.

The study findings were revealed at a time when the death toll from dengue has crossed the 500-mark this year, with another 13 new deaths reported in the last 24 hours till 8:00am yesterday.

Dengue infections are caused by four closely related viruses -- DENV-1, DENV-2, DENV-3, and DENV-4. These are called serotypes because each of them has different interactions with the antibodies in human blood serum, according to Nature, a science journal.

To learn more about the most circulated dengue serotypes in Dhaka, virologists at the National Institute of Laboratory Medicine and Referral Centre (NILMRC) tested 200 samples recently.

In the study, the DENV-2 serotype was detected in 151 samples, DENV-3 in 37, and both DENV-2 and DenV-3 in 12 samples, according to a press release sent by the NILMRC yesterday.

Interpreting the findings, Dr Arifa Akram, assistant professor at the Department of Virology at NILMRC, told The Daily Star yesterday, "This indicates that the DENV-2 may be one of the factors contributing to the higher fatalities in the country this year."

"But there are some other associated causes, such as second-time infection," she said.

She emphasised the necessity of conducting a study on the clinical characteristics of the patients to have a comprehensive understanding of the ongoing dengue outbreak.

"Unfortunately, we were unable to carry out such a study due to a lack of budgetary support," she added.

In June, the Institute of Epidemiology, Disease Control and Research (IEDCR) also found DENV-2 as the most prevalent serotype after testing 40 samples.

The IEDCR did not conduct any study on the clinical features of patients either.

Meanwhile, the NILMRC is making preparations to start dengue genome sequencing soon, read the press release.

Studies focusing on serotypes study and genome sequencing are very crucial to controlling the dengue outbreak.

"There should be more studies like this. Because we need adequate data to comprehend and control the dengue outbreak," Dr Be-Nazir Ahmed, former director of Disease Control unit at the Directorate General of Health Services (DGHS), told The Daily Star.

Stressing the lack of any well-coordinated action plan at the policy level, he said, "Unfortunately, we have yet to develop any systematic approach to fight dengue, though dengue turns severe every year."

The total number of dengue patients hospitalised so far rose to 1,06,429, including 2,070 new admissions yesterday. The total number of fatalities in dengue reached 506, the DGHS reported.