The capital is yet again experiencing an early outbreak of dengue and untimely rains may be to blame.

Like last year, Aedes mosquitoes, transmitter of the dengue virus, have bred early this year alarming authorities and city dwellers and health officials say there are chances their number would be larger.

This year, there have been frequent rains during January and April before the start of monsoon.

This outbreak comes after a record number of dengue cases last year and an outbreak of chikungunya last winter. Chikungunya is spread by the same mosquito.

At least 126 people were infected with dengue between January 1 and April 19, a number highest since 2000 for the same period, shows data from the health directorate.

In Bangladesh, most of the dengue cases are reported during June and October as intermittent rains and high temperature and humidity during the months create the ideal breeding conditions for Aedes.

However, the authorities last year saw a new trend of early dengue infection. During January and April 2016, at least 71 dengue cases were reported in the capital. At least 14 of them died. The total number of dengue cases that year was 6,020, the highest since 2002.

Pulak Priya Mutsuddy, an epidemiologist at the Directorate General of Health Services (DGHS), said of the total number of dengue cases between  2000 and 2015, less than one percent was reported in those four months. However, the percentage rose to over six percent last year.

Epidemiologists believe early rain could be a reason behind this early dengue cases. The Aedes prefers to breed in clean, stagnant water in containers following rain near households, roadsides ditches and other places.

Earlier, the Institute of Epidemiology, Disease Control and Research (IEDCR) recorded 19 cases of chikungunya during the last week of 2016 and the first week of this year.

Dengue and chikungunya have no specific treatment. The treatment is focused on relieving the symptoms, says the World Health Organization (WHO).

Dengue, which causes flu-like illness, can be fatal at times. Chikungunya, on the other hand, is not fatal, but causes fever and severe joint pain, muscle pain, headache, nausea, fatigue and rash. The joint pain may be prolonged to weeks, says WHO.

Prevention and control of dengue depends on effective mosquito control measures, it adds.

IEDCR Director Prof Meerjady Sabrina Flora said early rain could be a factor in the breeding of Aedes mosquitoes, but there are other factors too. For example, she said, there was no rain during the chikungunya outbreak last winter.

An investigation by the IEDCR and DGHS found that the sources of Aedes mosquitoes were drums filled with water in slum-like settlements in Kathalbagan and Kalabagan areas in the capital. That caused the chikungunya outbreak, said Sanya Tahmina, director (communicable disease) of DGHS.

“The water drums were not covered. Mosquitoes bred there and spread chikungunya,” she said.

A survey by DGHS last year found at least one in five homes in the Dhaka South City Corporation had stagnant water in containers with mosquito larvae or pupae.

The survey found mosquito   larvae or pupae mostly in plastic barrels, buckets, clay pots, used or abandoned tires, tubes and water tanks.

Prof Saif Ulla Munshi of virology at the Bangabandhu Sheikh Mujib Medical University said it was important for the authorities to gear up mosquito control programme. The programme includes destroying the larva and pupae before the monsoon begins.

“If larva is destroyed, mosquito population would not go up. Otherwise, early spread of Aedes means higher number of dengue cases,” he told The Daily Star.

On the other hand, people in general need to make sure that any flower vases, buckets or other pots in and around their houses did not have stagnant water, Prof Munshi said.

Contacted, DSCC Chief Health Officer (CHO) Brig Gen Sheikh Salahuddin said they were aware of the dengue situation and had regularly been spraying medicines to destroy Aedes larva and pupae.

The DNCC is also working with the same plan. CHO Brig Gen SMM Saleh Bhuiyan of DNCC said they were implementing mosquito control programme comprehensively as well amid rising trend of dengue.