JOIN USThe dengue virus subtypes that are circulating in Delhi this season are Type 2 and Type 4, according to a preliminary report by the All India Institute of Medical Sciences on Friday.
The subtype 4, which had been lying low in the previous few years, may be one of the factors behind the steep number of dengue cases this year.
On Wednesday, the Union Ministry had said the identity of the virus will be known in a week and the process of identifying the subtypes are going on at the AIIMS.
Of the nine samples tested at the AIIMS, four samples were found to be of the subtype DEN-2 and two of DEN-4.
There are four distinct serotypes of the virus that cause dengue — DEN-1, DEN-2, DEN-3 and DEN-4.
The capital has seen 831 cases so far with August alone recording 778 cases. This is an all-time high since 2010 when 885 cases were recorded in August itself.
DEN-4 has not been dominant in Delhi for last few years even though it has been present. From time to time, the four strains have been isolated in different states.
“DEN-4 has not been a predominant serotype in the last few years. This may have also contributed to the steep rise in dengue cases this season. This is because the population has not encountered the virus till now. Other factors like rainfall and related conditions have also contributed to the rising number of dengue cases,” said Dr Lalit Dar, professor at Microbiology Department, AIIMS.
The subtype 2 has been dominant for the last two years as well.
The AIIMS report stated, “While DEN-2 was the predominant serotype in circulation during the last two years, DEN-4 has been isolated very rarely in previous years.”
However, even though Delhiites have been exposed to the subtype 2, they have still not grown immune to it, said experts.
Symptoms
DEN-2 and DEN-4 are considered the most virulent types of strains. The symptoms of DEN-4 are, however, milder than that of subtype 2.
“The subtype-4 is not as severe as subtype-2,” said Dr Dar.
When a strain is more virulent, the symptoms of the infection are more severe among patients. When a strain is around for long, few people suffer from the virus.
In 2010, all the strains were present. Even though in the last two year fewer cases were witnessed, subtype 2 was around.