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Calculating the cost of chikungunya and dengue

5 Mar 2009

Paul Chinnock

Source: TropIKA.net

The Indian Institute of Management, Ahmedabad (IIMA) has made preliminary calculations of the likely economic impact of two diseases, dengue and chikungunya. Both diseases are spread by Aedes mosquitoes.

It has been clear for some time that dengue fever outbreaks are costly for national economies, as discussed in a recent TropIKA.net news story. However, there have been few attempts to quantify the impact either of dengue or of chikungunya, a disease which has only emerged during the last half century. The preliminary estimates made by IIMA, within two working papers, provide support for the view that the economic burden is considerable. For India as a whole, the researchers consider it to amount annually to around US$1.5 billion (range $0.6-3.5bn). This would equate to $1.6 for every person in India.

The estimates only extend to the ‘immediate’ costs of illness and mosquito control. Factors not considered include the burden due to long-term illness and death, and the consequences for education, foreign investment, economic growth etc. For several other disease-endemic countries, with higher income per capita, the costs are likely to be much greater.

Gujarat focus

In one IIMA working paper [1], the researchers focused on a single Indian state – Gujarat, population over 56 million and one of India’s more important states economically. The authors based their calculations on the number of dengue cases reported during a five-year period and the number of reported chikungunya cases over a three-year period. They estimated the cost of illness, allowing for reported and unreported cases, and hospitalised and ambulatory cases. (They took each reported case as being only 4% of the true total.) They also estimated the cost of vector control, including state and municipal expenditure, household spending on insecticides and private sector costs.

Using a technique known as Monte-Carlo analysis the researchers then calculated the total cost to Gujarat as being $90 million (range $38-214m), with 92% of this cost due to chikungunya illness, 3% due to dengue illness, and the remaining 5% the cost due to intervention activities. They then extrapolated from their Gujarat findings to derive their total figure of $1.5 billion for India as a whole. (Six states of India account for over 90% of the burden and number of cases of dengue and chikungunya.)

The authors point out that comparable per capita figures for the cost of dengue are US$ 5.3 in Malaysia and US$ 6.2 in Panama, while Brazil spends US$ 4.3 per capita on dengue prevention alone. The differences in these costs can be partially be explained by the roughly five times higher GDP per capita in these countries compared with Gujarat.

The working paper concludes that:

“As policy makers weigh investments in new technologies and expanded use of existing interventions to control neglected tropical diseases, the economic cost of illness is a major input into decision making. It is hoped that this preliminary estimate will trigger more refined studies on cost of illness as well as cost-effectiveness of vaccines and other interventions to combat these neglected tropical diseases.”

Tourism

IIMA researchers have also sought to quantify the likely impact of the two diseases on tourism [2]. In this case they made their calculations for Gujarat, Malaysia and Thailand. The authors worked on the assumption that only tourists from countries which are not chikungunya‐ or dengue‐endemic would be deterred from visiting, and that a severe outbreak could lead to 4% drop in tourism revenues.

They describe this as a conservative estimate, based on the experience of French Réunion and Mauritius, which had chikungunya outbreaks in 2006. Based on these assumptions, the findings of the study were that:

"A 4% decline in tourists from non-endemic countries would result in a substantial loss of tourism revenues - at least US$ 8 million for Gujarat, US$ 65 million for Malaysia, and US$ 363 million for Thailand. The estimated immediate annual cost of chikungunya and dengue to these economies is US$ 90 million, US$ 133 million, and approximately US$ 127 million respectively, indicating that impact on tourism revenues should not be ignored when calculating the burden of infectious diseases."

Gujarat has a relatively small tourist trade but the decline in revenue still adds significantly to the overall economic impact of dengue and chikungunya. Tourism is on a much larger scale in Malaysia and, even more so, in Thailand. A 4% decline in tourist numbers in the event of a severe outbreak in these countries would have massive economic consequences.

Again the authors emphasise that their finding are only preliminary but their figures make a strong case that tourism revenue should indeed be factored into such calculations, including cost-effectiveness studies of interventions.

References

1. Mavalankar DV, Puwar TI, Govil D, Murtola TM, Vasan SS (2009). A Preliminary Estimate of Immediate Cost of Chikungunya and Dengue to Gujarat, India. Indian Institute of Management, WP No. 2009-01-01.

2. Mavalankar DV, Puwar TI, Murtola TM, Vasan SS (2009). Quantifying the Impact of Chikungunya and Dengue on Tourism Revenues. Indian Institute of Management, WP No. 2009-02-03.

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