Early outbreak: Chikungunya up 100 times in Delhi, dengue cases at all time high

Delhi reported 365 cases of dengue and 246 cases of chikungunya by August 5 this year. The figures for the same period in 2016 were 171 and 2, respectively. Delhi government says the rise in numbers is because of better surveillance.

The number of dengue and chikungunya cases being reported from Delhi hospitals since January have risen exponentially this year than those recorded in the same period in previous years.

This year’s robust monsoon has come at a price: a zenith in the dengue and chikungunya cycles. Spiralling cases of both diseases have sent alarm bells ringing and the “season” has only just begun. (Sonu Mehta/HT Photo)

Delhi hospitals have reported 365 cases of dengue till August 5, more than double of 171 cases recorded during the same period in 2016, and triple than 119 cases in 2015 — the year when Delhi saw its worst ever dengue crisis.

As for chikungunya, a total of 246 cases have been recorded by the Municipal Corporation of Delhi (MCD) till August 5, compared to just two cases that were reported in the same period last year, when Delhi had a chikungunya outbreak.

“The reason that higher numbers of chikungunya cases are being recorded this year is because the surveillance is better. Last year, nobody had expected a chikungunya outbreak as the viral infection does not commonly spread in Delhi,” said a Delhi government official.

“It was only after hospitals started receiving hundreds of cases, that attempts to collect data were made,” the official added. After the outbreak, the corporation listed chikungunya as a notifiable disease, making it mandatory for hospitals to report chikungunya cases with district authorities.

Both the mosquito-borne illnesses are spread by the same day-biting aedes aegypti mosquito, which breeds in clean stagnant water. The mosquito population usually increases during the monsoons and that’s when the number of cases go up.

Is chikungunya here to stay in Delhi? Experts say it is too early to judge. “Dengue is endemic (regularly occurring in Delhi and we see cases of the disease every year, and even though chikungunya is spread by the same mosquito we cannot say it is endemic. We have to wait for a couple of years to see whether cases are observed regularly each year,” said Sujatha Sunil, group leader, Vector Borne Diseases Group, International Centre for Genetic Engineering and Biotechnology (ICGEB).

However, experts attributed two reasons for the high number of cases this year.

“Delhi had dengue and chikungunya outbreaks during the last two years. The cases that were recorded in the first couple of months this year are most likely spillover cases from the previous years,” said Dr Sunil.

This year, 32 cases of dengue were recorded between January and April, as compared to 7 in 2016 and 7 in 2015 during the same period.

Apart from this, the intermittent rainfall is also to blame.

“This year, Delhi has seen intermittent showers, which actually create breeding grounds for mosquitoes,” said a health department official.