In recent years, public health authorities have expressed serious concerns regarding what they call the trend of “emerging infections.” They fear that many diseases transmitted by various pests—collectively called “vectors”— are on the rise. Even diseases eradicated from the United States are reemerging as increased travel and trade create more opportunities for diseases to cross international boundaries. Even diseases that have never been seen in the United States have emerged, such as the West Nile virus in 1999.
In the past, we have been able to keep these diseases at bay with the use of pesticides and other measures, but today government regulations limit access to much-needed pesticides. In addition, environmental activists have waged attack campaigns on pesticide use, scaring the public about the risks of pesticides and failing to inform them of the far more serious risks associated with disease vectors. As a result, individuals and public health agencies have fewer options to control serious and expanding risks associated with vector-borne diseases.
Throughout history, one of the most serious risks to public health has been disease transmitted by vectors. Vectors include any organism that carries pathogens that can then be transferred to humans. Most commonly we think of mosquitoes and other insects, but rodents and other animals can transmit disease as well. We should learn from history that vector-borne risks are not isolated to tropical areas and that they can reemerge in the United States. Consider a few historical cases:
• In the summer of 1793, an epidemic of yellow fever, a disease carried by mosquitoes, struck Philadelphia. Yellow fever killed 5,500 people that summer and plagued the city for seven years.
• Malaria was endemic in most of the United States and remained so in many states until right after the end of World War II.
• Dengue fever periodically emerged the U.S. Gulf Coast states for decades including recent outbreaks in the 1980s, and it continues to pose a threat. Tick-borne diseases have affected the population as well.
• The research of Paul Reiter, chief of the entomology section of the Dengue Branch of the Centers for Disease Control and Prevention (CDC), demonstrates that, contrary to popular wisdom, most mosquito-borne diseases are not tropical. For example, he notes that until modern times, malaria was endemic in nearly all states east of the Rockies, as well as in Canada, Norway, Sweden, and northern Russia.