Increased Distributions of Mosquitoes and Ticks
May 21, 2016
Nick Bradford

Did you know?

  • Children ages 5-9 have the highest annual incidence of Lyme disease in the United States.
  • West Nile Virus has been observed in 65 mosquito species and 300 bird species in the United States. 

A vector-borne disease is one that is transmitted by a living organism between humans or from animals to humans. The most common in the United States are distributed by vectors such as fleas, ticks, and mosquitoes and include Lyme disease, Dengue fever, West Nile virus, and Rocky Mountain spotted fever.

As the climate becomes warmer, these vectors are able to expand their ranges and potentially expose more people to infection. For example, the graph below shows how the geographic distribution of ticks and cases of reported Lyme disease in the northeast and upper midwest have increased from 2001 to 2014 partly due to warmer winters and changes in precipitation


Changes in Lyme Disease Case Report Distribution

In addition to warmer winters and changing precipitation patterns, the distribution of mosquitoes and cases of reported West Nile have also increased in the US, partly due to changes in bird migration patterns and increases in extreme weather events. Birds are the natural host of West Nile virus and the disease can be transmitted to humans from mosquitoes. The maps below show the incidence of West Nile in the US from 2010 through 2013, shown as cases per 100,000 people.  


Incidence of West Nile Neuroinvasive Disease by County in the United States

Geographic location and individual characteristics, such as age, gender, and immune function, influence the likelihood of someone being infected by a vector-borne disease. For instance, children are more susceptible to insect bites because they generally spend more time outdoors than adults and are dependent upon adults to take preventative measures. 

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