Rains, rising temperature, humidity important risk factors

Islamabad
After the first rain spell of monsoon in the region, the chances of incidence and spread of dengue fever have increased as almost all risk factors considered to be the most important for appearance of seasonal dengue fever have become very much in existence.
Rains, rising temperature, humidity and import of infected travelers are considered to be the most important factors for spread of the infection.
Data collected by ‘The News’ has revealed that so far, a total of four confirmed patients of dengue fever have been reported at Holy Family Hospital in town of which three reached in town from Saudi Arabia while one was from Karachi.
Not a single case of dengue fever has been reported from Rawalpindi so far as all confirmed patients who reached HFH got infection from KSA or Karachi, said Executive District Officer (Health) Dr. Nasir Mehmood while talking to ‘The News’.
It is important that the effects of temperature, humidity and rainfall along with artificial flooding, the man-made watering of lawns, fields and water spillage, are the genuine factors besides movement of infected patients from areas where there has recently been an outbreak of dengue fever to cause the disease.
Usually, ‘aedes aegypti’, the mosquito that causes dengue fever lay the first eggs of the year at the beginning of May and the mosquito density is maximal in early July, late August and early September while the egg laying activity remains until November though the larval density reaches to its peak in September, said Assistant District Health Officer Islamabad Capital Territory Dr Muhammad Najeeb Durrani who is an epidemiologist while talking to ‘The News’ on Wednesday.
He added that the risk of incidence and spread of dengue fever is on the rise. The population of ‘aedes aegypti’ fluctuates with temperature, rainfall and humidity. Dengue infections were generally encountered during or after rain, as an outcome of rise in vector population, he said.
He explained that the optimal temperature for ‘aedes aegypti’ larva is 28 degree centigrade and above this the rate of development is high and below 18 degree centigrade, the growth gets prolonged. Above 36 degree centigrade, the larval development is not complete. Extreme hot and dry weather may kill most of the eggs but in humid weather, the populations increases rapidly, said Dr. Durrani.
It is time to take preventive measures more seriously to avoid breeding and growth of mosquitoes as the population of ‘aedes aegypti’ is high in rainy season and the conditions in monsoon in the region become much favourable for mosquitoes to grow, he said.
He added that during rainy season, the risk of virus transmission by the vector is greater. Control measures of Aedes aegypti larva is necessary as dengue fever (DF) and dengue haemorrhagic fever (DHF) cases increase proportionally with the larval density, he said.
He added the ICT Health Department has organised dengue control programmes with aims to reduce the mosquito-genic sites and to control the population of immature and adult aedes aegypti.
He said it is time to educate public on aspects related to dengue fever incidence and spread. He added the mosquitoes have three water dependent stages including eggs, larva and pupa and the last aerial stage of adult mosquitoes.
As an epidemiological finding we always expect a surge in dengue fever cases after the rains when an outbreak is already occurring in adjoining areas, districts or other parts of the country. This is high time when we can start social mobilization to contact community to look for sites and places inside or outside homes that can attract rain water and provide a favourable place for the female aedes mosquitoes to lay eggs, he said.
Through awareness campaigns, there is a need to convince community to keep vigilance as they should destroy the possible breeding sites mechanically that can harbor larvae to develop into adult mosquitoes, said Dr. Durrani.