New Delhi: Given its close link with both temperature and rainfall, it is possible to forecast outbreak of dengue. But for such disease forecasting to be effective it should be based on models specific for different climatic zones in the country, a new study has shown.
Scientists have reached this conclusion after evaluating the relationship of climatic factors in the spread of dengue in different climatic zones in the country – Punjab, Haryana, Rajasthan, Gujarat, and Kerala. They focused on changes in a factor called ‘extrinsic incubation period (EIP) of the dengue virus by taking into account daily and monthly mean temperatures in these areas.
The extrinsic incubation period (EIP) is the time taken for incubation of the virus in the mosquito. During this period, after the mosquito draws virus rich blood meal, the virus escapes the gut and passes through the mosquito’s body and reaches it salivary glands. Once this happens, the mosquito is infectious and capable of transmitting the virus to a human host.
It has been found that climatic conditions play an important role in EIP. Lower temperatures (17–18 °C) result in longer EIPs thereby leading to decreased virus transmission. With increasing temperatures, feeding increases because of enhanced metabolism of the mosquito, leading to shorter EIPs. Even a 5-day decrease in the incubation period can hike transmission rate by three times, and with an increase in temperature from 17 to 30 °C, dengue transmission increases fourfold. However, a further increase in temperature beyond 35 °C is detrimental to the mosquito survival.
Picture: Dr Mutheneni (second from right) with his team at IICT, Hyderabad.