Please check out this link below from Prevent Mosquitoes.org for additional information about how mosquitoes spread diseases. 
https://www.youtube.com/watch?v=qW252a2a2k0 

• Mosquito-borne diseases of man offer special challenges to those trying to prevent or control disease outbreaks. First, with the sole exceptions of yellow fever and Japanese encephalitis, vaccines licensed for use in humans are not available.
• The mosquito-borne disease surveillance program monitors and detects arbovirus activities to minimize the risk of human infections throughout Indian River County.
• IRMCD participates in a State-sponsored program of surveillance for the detection of several mosquito-transmitted viruses (St. Louis encephalitis, West Nile, and Eastern Equine encephalitis viruses). This program has been in place since 1978.
• The SLE/WNV surveillance program conducted by IRMCD has two inseparable components. The first component is the use of sentinel chicken flocks to monitor levels of virus transmission from mosquitoes to birds in the county. There are 8 sentinel chicken sites located throughout the county to assess local mosquito transmission of West Nile virus, St. Louis encephalitis, and Eastern equine encephalitis in birds. The second component involves the intensive monitoring of two representative populations of the principal vector mosquito,
• Culex nigripalpus is in different parts of the county.  Mosquito population monitoring utilizes specialized adult mosquito trapping techniques to monitor changes in the abundance and behavior of the vector mosquito Culex nigripalpus.
• Unlike the encephalitis viruses, there are no useful early detection monitoring programs for dengue, chikungunya, or Zika viruses. Since these viruses are transmitted from mosquito to man, the only indication of the virus in Florida will be the reporting of a human case.
•  Human case investigation involves determining when and where a disease was contracted. A close working relationship with our local Florida Department of Health helps to determine when and where the mosquito-borne disease was contracted and whether it was acquired locally or travel-related outside of the County.