The prevalence of diseases caused by ticks, mosquitoes, and fleas that feed on the blood of humans has increased dramatically. Over a 13-year span (the years 2004 through 2016), the incidence of tick-, mosquito-, and flea-borne diseases in humans has more than tripled in the United States. In 2004, there were 27,388 reported disease cases spread by the bites of infected ticks, mosquitoes, and fleas. However, in 2016, this number increased sharply to 96,075 reported cases. The reasons for this notable surge are the result of a number of factors that favor the preponderance of the aforementioned vectors (agents that are capable of biologically transferring a pathogen from one organism to another) and that aid in the transmission of vector-borne diseases: climate warming trends have extended the length of summer seasons, which are also hotter; the ease and rapidity of travel by humans and goods (and any vectors that may accompany them) across vast distances continue to grow; and people are visiting and inhabiting previously unsettled or pristine areas that harbor various vectors (for example, more suburban developments are being built in or near wooded areas, where ticks reside). In addition, nine new pathogens that are spread by mosquitoes and ticks have been reported in the United States over this time period; these include the germs responsible for Zika virus disease, chikungunya fever, Heartland virus, and Bourbon virus. See also: Acari; Chikungunya virus disease; Diptera; Economic entomology; Global warming; Infectious disease; Mosquito: vector of disease; Pathogen; Siphonaptera; Zika virus disease; Zoonoses
According to the Centers of Disease Control and Prevention, more than 75% of the reported cases of vector-borne diseases in the United States are spread by ticks. Lyme disease accounts for the vast majority (82%) of all tick-borne illnesses, with anaplasmosis, ehrlichiosis, babesiosis, Powassan virus, spotted fever rickettsiosis, and tularemia accounting for the remainder of cases caused by ticks. With regard to the mosquito-borne cases, the most prevalent diseases are West Nile virus and Zika virus disease. In addition, another seven diseases are transmitted by mosquitoes: California serogroup viruses, chikungunya virus disease, dengue fever, Eastern equine encephalitis virus, malaria, St. Louis encephalitis virus, and yellow fever virus. Although flea-borne cases are much fewer, endemic plague is the chief disease caused by fleas, amounting to about 17 cases per year. See also: Anaplasmosis; Arboviral encephalitides; Dengue fever; Ehrlichiosis; Encephalitis (arboviral); Lyme disease; Malaria; Plague; Rickettsioses; Tick virus diseases; Tularemia; West Nile virus; Yellow fever
The increase in vector-borne diseases in not limited to the United States. Mosquito-, tick-, and flea-borne illnesses are on the rise around the world. In fact, these types of diseases are responsible for approximately 17% of all instances of infectious disease, and they cause at least 700,000 deaths per year. Unless preventative measures are undertaken to control and eliminate infected vector populations that carry a variety of traditional and emerging pathogens, the expansion of these vectors across the globe will continue, inevitably leading to future epidemics. See also: Disease ecology; Epidemic; Public health