When the State’s health system was busy focussing on containing the Nipah outbreak in Kozhikode, the arrival of the southwest monsoon has brought in infectious diseases such as dengue.
Dengue cases are being reported from northern districts, with most cases being reported from Kasaragod, Malappuram and Kannur. In the past four days alone, six fever-related deaths, including two suspected dengue deaths, have been reported from the northern districts
“In two weeks’ time, vector density will explode and then things will just go out of hand. Nipah outbreak is likely to be contained soon, but dengue is there for the long haul and thousands will be affected,” a senior public health expert said.
Even though the peaks in dengue incidence and serotype dominance followed a regular cyclical pattern, Kerala had been endemic to dengue for so long that there could be no predictions as to the possible case burden or the severity of the outbreak year after year, he said.
However, this year, the northern districts of Kerala are expected to bear the brunt of dengue case burden. Going by the current pattern of incidence, Kasaragod and Malappuram have been reporting more cases.
“We think the dengue case burden might not be as alarming as it was last year. But the mortality rate will depend on the dominant dengue virus serotype this season. Last year, while a chunk of our case burden was due to serotype 2, in Thiruvananthapuram, nearly 55% of the cases were due to serotype 1, which also accounted for the severity of the outbreak,” said T. S. Anish, Associate Professor of Community Medicine, Government Medical College Thiruvananthapuram.
In circulation
All four dengue virus serotypes are in circulation in Kerala, but till now serotype 4 has been less common, with a few cases being reported from pockets in Thiruvananthapuram and Kollam.
“Last year, the huge dengue outbreak in Tirunelveli, just across the border in Tamil Nadu, had been due to serotype 4. Thiruvananthapuram, which accounted for 41% of the State’s case burden last year, could have a severe outbreak with high case fatality if at all the density of mosquitoes carrying serotype 4 goes up,” E. Sreekumar, a senior scientist at the Rajiv Gandhi Centre for Biotechnology, said.
Globally, 80% of dengue cases appear as subclinical infections. Infection by one serotype of dengue virus renders a person immune to that serotype for life. But he stands the risk of having a severe and more complicated dengue infection (expanded dengue syndrome) if he is again afflicted by dengue but with another serotype of the virus (the phenomenon is called “antibody dependent enhancement”).
Given the annual dengue epidemics in the State, the increasing dengue case burden thus exposes people to the larger risk of being afflicted by a more severe infection next season, increasing the case fatality rate. Already, the seroprevalence of dengue (detection of dengue-specific antibodies in blood) among 9-12 year-old children in the capital is 42% and it is expected to be much higher in adults.
As yet another season of dengue looms large, it is this huge risk of secondary dengue infections in the community, which could result in more complications and a higher mortality rate, that is worrying the Health Department.
