Ecology: The Delicate Balance of Life on Earth

Ecology: The Delicate Balance of Life on Earth — page 7
EcoLOGY THE DELIATE BALANCE OF LIFE ON EARTut programs to control infectious diseases For example the rapid spread of West Nile virus WNV in the United States in the early 21st century resulted from the interaction of environmental factors with human and animal populations Mosquitoes spread the virus by biting infected birds and then bit ing humans and other animals One study in Florida noted that the number of WNV cases was especially high for years in which a dry spring season was followed by an especially wet summer Further studies of environmen tal factors suggested that the limited water resources resulting from a dry spring may drive mosquitoes to congregate in isolated patches of dense vegetation where condi tions remain humid These humid patches also serve as nesting sites for an array of wild birds In the close quarters of this temporary home mosquitoes feed on and infect more birds than usual When conditions change and the mosquitoes break out of their group ings and scatter more people than usual will be bitten by these mosquitoes and become infected Such insights gained from recognizing environmental factors promoting infection and transmission are crucial for fighting 12