To prevent dengue... turn down your lights

Can the mosquito that spreads dengue and chikungunya bite during the night? Yes, it can. Though the probability of being bitten by a dengue- and chikungunya-spreading Aedes aegypti mosquito, which breeds in fresh water, is higher during the day, a night bite can also cause infection.

The dengue-spreading mosquito is a day-biting mosquito that is most active for around two hours after sunrise and several hours before sunset but it also bites at night in well-lit areas.

“The female Aedes aegypti has a natural day-and-night diurnal rhythm and feeds at dawn and dusk,” said Dr Sujatha Sunil, group leader, vector borne diseases group, International Centre for Genetic Engineering and Biotechnology, New Delhi. Diurnal rhythm is biological pattern in tune with the day and night cycle.

Once they have had their fill of blood, they become inactive and rest in dark spaces. “Since light and temperature affects their feeding behaviour, artificial light and temperature that mimic the natural ambient climate can affect their feeding behaviour,” she said.

The risk is highest inside offices, malls, indoor auditorium and stadia that use artificial lights through the day and night and have little or no exposure to natural light.

“In these situations, the mosquitoes are unable to follow their natural day-and-night cycle and get confused,” Sunil said, adding that was the reason researchers simulate lighting and temperature conditions when doing experiments with mosquitoes.

The dengue mosquito lies low — it approaches from behind to bite ankles and elbows.

Loose clothes that cover arms and legs and repellents were the best protection, said Dr Srikant Sharma, senior consultant of medicine at Moolchand Medcity.

Delhi reported close to 300 dengue cases in the week ending August 26, taking the 2017 count to 945, with experts predicting rising malaria cases as well.

Dengue used to be a bigger threat in the Capital and its neighbourhood till last year the Capital saw its first chikungunya outbreak, with 7,760 cases. This year, Delhi has already reported 339 cases so far.

India has confirmed 36, 635 cases and 58 dengue deaths till August 20, the last date till for which data is available from all states.