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Research Article

# Unforeseen Costs of Cutting Mosquito Surveillance Budgets

• gmvazqu@emory.edu

Affiliation: Department of Environmental Studies, Emory University, Atlanta, Georgia, United States of America

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• Affiliations: Department of Environmental Studies, Emory University, Atlanta, Georgia, United States of America, Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica

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• Affiliations: Cairns Tropical Public Health Unit, Queensland Health, Cairns, Queensland, Australia, School of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Cairns, Queensland, Australia

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• Affiliation: Cairns Tropical Public Health Unit, Queensland Health, Cairns, Queensland, Australia

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• Affiliation: Department of Environmental Studies, Emory University, Atlanta, Georgia, United States of America

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• Published: October 26, 2010
• DOI: 10.1371/journal.pntd.0000858

## Abstract

A budget proposal to stop the U.S. Centers for Disease Control and Prevention (CDC) funding in surveillance and research for mosquito-borne diseases such as dengue and West Nile virus has the potential to leave the country ill-prepared to handle new emerging diseases and manage existing ones. In order to demonstrate the consequences of such a measure, if implemented, we evaluated the impact of delayed control responses to dengue epidemics (a likely scenario emerging from the proposed CDC budget cut) in an economically developed urban environment. We used a mathematical model to generate hypothetical scenarios of delayed response to a dengue introduction (a consequence of halted mosquito surveillance) in the City of Cairns, Queensland, Australia. We then coupled the results of such a model with mosquito surveillance and case management costs to estimate the cumulative costs of each response scenario. Our study shows that halting mosquito surveillance can increase the management costs of epidemics by up to an order of magnitude in comparison to a strategy with sustained surveillance and early case detection. Our analysis shows that the total costs of preparedness through surveillance are far lower than the ones needed to respond to the introduction of vector-borne pathogens, even without consideration of the cost in human lives and well-being. More specifically, our findings provide a science-based justification for the re-assessment of the current proposal to slash the budget of the CDC vector-borne diseases program, and emphasize the need for improved and sustainable systems for vector-borne disease surveillance.

## Author Summary

Surveillance has served as a basis for important public health responses to new threats, and as a source of invaluable information for health providers and policy makers. A budget proposal to stop the U.S. Centers for Disease Control and Prevention (CDC) funding in surveillance and research for mosquito-borne diseases such as dengue and West Nile virus has the potential to leave the country ill-prepared to handle new emerging diseases and manage existing ones. The present article uniquely integrates infectious disease models with economic analysis, taking advantage of a unique detailed dataset. By coupling a mathematical model with cost analysis we were able to evaluate the impact of delayed control responses to dengue fever, a mosquito-transmitted disease of global importance, in an economically developed urban environment. Our analysis clearly shows that the total costs of preparedness through surveillance are far lower than the ones that follow the introduction of vector-borne pathogens. Our findings will help provide a science-based justification for re-assessment of the current proposal to slash the budget of the CDC vector-borne diseases program. More generally our study demonstrates the power of rigorous analysis of carefully collected data for a balanced assessment of the economic implications of a public health program shift.

### Results and Discussion

The dengue outbreaks in Cairns demonstrate the vulnerability of developed countries to mosquito-borne pathogens that are major international public health concerns [7]. Our analysis shows that delaying control responses translates into an exponential increase in both the number of human cases and health costs (Figure 1). The cumulative cost of a strategy with active surveillance and res of 2 was US$0.15 and US$1.1 million for 2003 and 2009 epidemics, respectively (Figure 1). Responding to the same outbreaks 4–6 weeks later (res = 6–8) would have resulted in cumulative costs of containing the 2003 and 2009 outbreaks that are 86 (or US$13 million; Figure 1 C) and 346 (or US$382 million; Figure 1 D) times as high, respectively, than a strategy based on ongoing active surveillance. By the 9th week of an outbreak the costs accrued in controlling it increased exponentially and far surpassed the costs of a strategy with sustained surveillance and early case detection (res = 2) (Figure 1 C–D). Thus, a delayed reaction to both Cairns dengue outbreaks would have resulted in drastically escalated total costs of up to US\$ 382 million. Indeed, a slight difference in the virulence of the invading strain (ΔR0 = 0.1 between outbreaks) would have increased total costs by one order of magnitude (Figure 1 C–D). Notably, our predictions show that the costs to contain the 2009 outbreak in a city with a climate comparable to Miami, but with <10% of the population, would have been an order of magnitude higher than the proposed CDC budget cut that will impact the whole US.

Without a strong human and vector surveillance system, detection and response to emerging vector-borne diseases that can present, in many instances, undetermined symptoms in humans could be severely impaired. The emergence of WNV in New York City in 1999 is a clear example of the consequences that a delayed response can have on the outcome of a novel arboviral introduction [8], [9]. The first glimpse of WNV transmission occurred with the notification of unusual bird deaths in late June. The incorrect diagnosis of a cluster of human cases as St. Luis encephalitis in late August prompted the initiation of vector control actions, almost 2 months since the detection of bird deaths [8], [9]. By the time vector control was in place and WNV confirmed as the putative source of human and bird infections, the infection could not be contained (particularly in the bird population), and subsequently progressed throughout the US, generating 28,961 WNV human cases and 1,130 fatalities by the end of 2008 [10]. Vector-borne disease surveillance in the U.S. improved significantly after this failure to contain WNV [11]. A strong network of state and local health departments rely on CDC funds for personnel and routine seasonal testing of mosquitoes for WNV and other viruses. Indeed, one of the reasons the recent emergence of dengue in mainland US (after a 50-year hiatus [12]) was rapidly detected and contained is the through the presence in Florida of the CDC-supported vector surveillance network.

Without CDC funds, mosquito testing would be halted, and detection of transmission events or novel viral introductions significantly delayed (with response delayed by even more than 8 weeks), turning CDC into a reactive rather than preventive health service. Our analysis clearly shows that the total costs of preparedness through surveillance are far lower than the ones needed to respond to the introduction of vector-borne pathogens, even without consideration of the cost in human lives and well-being. Our economic analysis provides strong ammunition from an ethical, economic and scientific standpoint for lawmakers to retain the investments in this cost-effective preventive public health strategy. In fact, our analysis points to the need for more, rather than less, funding for vector-borne disease surveillance. The probability for early detection of an introduction of a vector borne disease agent, or for rapid interruption of transmission if an outbreak were to occur, are a direct function of adequate funding for vector borne disease research and surveillance.

### Acknowledgments

We thank Helen Faddy from the Australian Red Cross Blood Service for providing data on costs of blood-bank screening.

### Author Contributions

Conceived and designed the experiments: GMVP LFC SAR UK. Performed the experiments: GMVP LFC. Analyzed the data: GMVP LFC. Contributed reagents/materials/analysis tools: SAR JD. Wrote the paper: GMVP LFC SAR UK.

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