HYDERABAD: A study by scientists from Indian Institute of Chemical Technology - Hyderabad, University of Liverpool and NIPER-Guwahati has for the first time highlighted the association between weather and Extrinsic Incubation Period (EIP) of dengue virus in the mosquito, for different states of India. Findings of the study have opened up avenues for development of climate-based forecasting models for dengue outbreak. EIP is the time that elapses between a mosquito sucking dengue infected blood of a person to the time the dengue virus incubates inside mosquito’s body and the mosquito is ready to infect another human with its bite through saliva. EIP plays a crucial rule in fighting dengue which has infected close to 4,80,000 people and killed 1,374 across India since 2010.
The study, which has Dr Srinivasa Rao Mutheneni of IICT as the lead author, reported how ‘optimum’ climate conditions help in quicker incubation of dengue virus inside the mosquito, which make the mosquito ready to spread the disease earlier than the time taken during normal climatic conditions. This establishes a link between optimum climatic conditions and number of cases and incidences of disease outbreak. In the study, it was found that Kerala has the lowest EIP.
One of the main reasons behind the shortest EIP duration in Kerala compared to other states like Punjab where it ranged from 6 to even 96 days is because Kerala provided the right temperature and weather for dengue virus to incubate quickly inside a mosquito. This increases the probability of high number of people getting infected. Not surprisingly, as per figures of National Vector Borne Disease Control Programme, Kerala had the highest number of dengue cases until August 20 this year - 16,530 out of 36,635 across India and reported 28 deaths of 58 across country.
When contacted, Dr Mutheneni said, “Our study has shown how EIP is an important factor which should be kept in mind for tackling dengue and how the climatic conditions play a crucial role in decreasing EIP. Further studies should focus on development of forecasting models by climatic zone and seasons.”
Dengue spreads fastest in Kerala
The researchers estimated EIP using daily mean temperature data for five states. It was found that Kerala had the lowest EIP across all seasons of the year - between 9-14 days, which means that mosquitoes in Kerala could become ready to spread dengue within maximum 14 days once they get infected by dengue virus.