On Monday, Delhi Chief Minister Arvind Kejriwal tweeted the “stunning results” of his government’s campaign to get people to invest 10 minutes every week to stop dengue mosquitoes from breeding: “The number of cases in Delhi so far is just 356, compared to 650 by this time last year”, he posted; “most importantly, we have not lost a single life yet”.
To put this success in perspective, it is important to note three things.
This is a low dengue year
The data sheet on the “Dengue/DHF Situation in India” uploaded by the National Vector Borne Disease Control Programme (NVBDCP) of the Union Ministry of Health and Family Welfare contains numbers up to only May 26 of this year — well before the onset of the dengue season. Until then, the country had seen only five dengue deaths — three in Kerala, two in Maharashtra.
More recent data — albeit of dengue cases, not deaths — were furnished to Rajya Sabha by the Ministry in July. Until the end of June, only 8,058 cases of dengue had been reported countrywide — less than 8% of the 1,01,192 cases reported by NVBDCP for the entire year in 2018. Four deaths from dengue were reported in Delhi last year, according to the NVBDCP data.
The data given to Parliament show that until June, the largest number of dengue cases this year were reported in Karnataka (1,933), followed by Tamil Nadu (1100), and Maharashtra (969). Twenty two out of 34 states and Union Territories that reported data had fewer cases than in Delhi (91). West Bengal has stopped reporting cases to the Centre.
Dengue comes in cycles
Most experts agree that dengue comes in cycles — which means, it is only after every few years that a significant spike is seen in the incidence of the disease. The NVBDCP data show 15,867 cases in Delhi in 2015, followed by 4,431, 9,271, and 7,136 cases in 2016, 2017, and 2018 respectively. Factors such as the amount of rainfall in a particular monsoon, levels of public awareness, and the efficiency of the state’s response also play a role.
Dr P K Sen, a former director of the NVBDCP, said: “Dengue is cyclical, every 3-4 years there is a spurt. During the last few years, IEC (Information, Education and Communication) activities have been stepped up across the country, and measures have been taken early. People are more aware about the dangers of accumulated water; the breeding of Aedes mosquito (which is the carrier of dengue) has gone down greatly in the last three years. Environmental factors such as El Niño (which has an impact on the monsoon) also influence the virulence of the outbreak.”
Confirmation is not critical
A dengue death is not classified as one unless the serological tests that isolate and identify the virus returns positive. Dengue is a notifiable disease, but a case is required to be notified only when the confirmatory test has been done in the lab. Importantly, however, the confirmation of dengue infection is not key to its treatment, which can proceed and even conclude without that test being done.
“A suspected dengue case can be treated without any compromise in the quality of care even without confirming the suspicion. It is a viral fever, so doctors have to essentially watch out for dehydration, provide symptomatic relief, and keep a sharp eye on the platelet count so that the fever does not progress to the haemorrhagic variety,” said a senior doctor at a Delhi government hospital, who did not want to be named.
“All of this”, the doctor said, “can be done without the serological test, and this is routine in government hospitals where resources are limited. It also keeps the official ‘dengue numbers’ low. In theory, therefore, it is possible to have zero dengue deaths even when people have actually succumbed to the disease.”