Burden of chikungunya in India: estimates of disability adjusted life years (DALY) lost in 2006 epidemic.

BACKGROUND & OBJECTIVES: During 2006, chikungunya emerged as a major ever known epidemic in India. Disability adjusted life years (DALY) is an appropriate summary measure of population health to express epidemiological burden of diseases. We estimated the burden due to suspected chikungunya using DALYs for the first time and compared between the states and also with the burden due to other vector-borne diseases in India. The economic burden was also assessed in terms of productivity loss.

METHODS: Data on the reported cases of fever/suspected cases of chikungunya from different states during 2006 in India were used. Years lived with disability (YLD) were calculated for non-fatal cases to estimate DALY. Since the disability weight for chikungunya is not available, the weights available for rheumatic arthritis, comparable to the disease outcome of chikungunya were used for the estimation. The burden was estimated for both acute and chronic cases. It is considered that about 11.5% of cases were reported to have extended morbidity with persisting arthralgia. For acute disease, the average duration of illness was considered to be nine days and for chronic cases it was six months on an average. The productivity loss due to income foregone by the working class was calculated using minimum official wage.

RESULTS: National burden of chikungunya was estimated to be 25,588 DALYs lost during 2006 epidemic, with an overall burden of 45.26 DALYs per million. It varied from 0.01 to 265.62 per million in different states. Karnataka alone contributed as high as 55% of the national burden. Persistent arthralgia was found to impose heavy burden, accounting for 69% of the total DALYs. The productivity loss in terms of income foregone was estimated to be a minimum of Rs. 391 million.

INTERPRETATION & CONCLUSION: The chikungunya epidemic in the year 2006 imposed heavy epidemiological burden and productivity loss to the community. The burden of chikungunya in terms of DALY was estimated for the first time. In view of re-emergence and spread of this infection in recent times it is warranted for derivation of disability weight for different health states of chikungunya to facilitate realistic estimates of DALYs. Quality epidemiological data from surveillance system to monitor vector-borne and zoonotic diseases would pave way for more realistic estimates of burden. The productivity loss in-terms of income foregone could be minimal as the estimation was made by using the minimum wage fixed by the government although the actual loss is expected to be higher.