2. Introduction

Emerging infectious diseases are a growing aspect of global change. These diseases are major challenges for public health, agriculture, and wildlife management. Most infectious diseases of humans originate from other host animals, and many are transmitted by an insect vector such as a mosquito. Examples include malaria, yellow fever, and West Nile virus. Controlling host-vector diseases can be very difficult.

This study focuses on the outbreak of the emerging infectious disease West Nile virus in North America. West Nile virus is a host-vector disease: the main hosts are birds and the vectors are mosquitoes, as shown in FIGURE 1.

A West Nile virus infection can be fatal for birds and mammals, including humans. Beginning in 1999, the virus spread across the continent, causing an unexpectedly high number of bird, horse, and human fatalities (FIGURE 2). This surprising effect prompted a strong public health interest in understanding, preventing and controlling West Nile virus outbreaks.

Since West Nile virus lives in mosquitoes and birds, it could conceivably be controlled by eradicating mosquitoes or eradicating birds. Which of these approaches would be more effective? The following experiment would provide the answer: eradicate mosquitoes in one set of places, eradicate birds in another, and compare them to see which worked best. However, that experiment would be expensive, time-consuming, and potentially disastrous, particularly for the birds. Instead, we used a mathematical model to investigate how the reduction of bird and/or mosquito populations would affect a West Nile virus outbreak.

Results Q2