Hamilton County Public Health

Guide to Mosquito Control & Mosquito-borne Illnesses

Mosquito-borne Illness

There are several illnesses that can be transmitted to humans by mosquitoes. The most common in our area is West Nile Virus. In 2016, Zika Virus showed up locally in people who returned from parts of the world where the virus is common. You can reduce your risk of being infected with mosquito-borne illness by using insect repellent and wearing protective clothing to prevent mosquito bites.


West Nile Virus (WNV)

Most people (about 4 out of 5) who are infected with West Nile virus will not develop any type of illness (an asymptomatic infection). However, WNV can also lead to West Nile Fever or Severe West Nile Disease. The incubation period is usually 2 to 15 days.

West Nile Symptoms:

  • Fever
  • Headache
  • Tiredness
  • Body aches


Zika Virus

Zika virus can be transmitted from mosquitoes to humans, from a pregnant woman to her unborn baby, and from an infected man to his sex partners. Most people (about 4 out of 5) who are infected with Zika virus will not develop any type of illness (asymptomatic). However, about 1 in 5 people infected with Zika virus become ill (i.e., develop Zika). The incubation period (the time from exposure to symptoms) for Zika virus disease is not known, but is likely to be a few days to a week.

Zika Virus Symptoms:

  • Fever
  • Rash
  • Joint Pain
  • Conjunctivitis (red eyes)



Why Mosquitoes Bite

Mosquitoes are attracted to an individual based on a complex interaction of the many chemicals you exhale, perspire or w ear. Only females have piercing and bloodsucking organs. Hosts include humans and domestic animals, and vary with the species.


Avoid Mosquito Bites

  • Be aware of peak biting periods.
    • Evening and early morning hours.
  • Avoid infested areas.
    • Shaded, humid areas with little or no breeze
    • Tall grasses/weeds
  • Wear light-colored, loose-fitting clothing.
    • Long sleeved shirt, long pants, jacket
    • Tuck pant legs into boots/socks
  • Use appropriate chemical repellents for your skin. Follow directions on product.
    • Aerosol/pump sprays, sticks, soaps, lotions, creams & towelettes
    • Most effective repellents contain DEET (N-diethyl-metatoluamide), Picaridin (KBR 3023) or Oil of lemon eucalyptus [p-menthane 3.8-diol (PMD)], which should be listed in the ingredients
  • Equip/repair all doors/windows with 16-mesh screen.



Drain Standing Water

By draining standing or stagnant water on your property you eliminate mosquito breeding sites and help reduce the mosquito population around your home. The chart below identifies items typically found around the home that can collect water and provides solutions for keeping them free of stagnant water.

Breeding Sites
Examples Solution
Swimming Pools abandoned properly fill or tear down
active maintain sanitizers and filters
wading/children empty after each use
Containers old tires, pet bowls, buckets, flower pot saucers, bottles, cans, tire swings, garbage cans/lids, rain barrels/basins keep empty, remove, or cover
Any area where water can collect in a stagnant situation ditches clear debris and keep drained
low areas/ruts fill with dirt and reseed
bird baths empty frequently
fountains maintain water circulation
ornamental water garden stock with mosquito-eating fish
ponds, creeks, lakes minimize plant growth and maintain water circulation
boats store covered or upside down
leaking water spigots repair leaks, maintain spigots
clogged gutters (even those with gutter guards) clean and maintain regularly
tree rot holes, hollow stumps fill hole or remove tree/stump
pooled sewage contact your local public health agency




Larvicides are chemicals or natural bacteria that can be used to kill mosquito larvae in standing water that cannot be drained. They are the most effective form of mosquito control because they kill mosquitoes before they become adults and disperse by flying. Larvicides are more commonly referred to as mosquito “dunks.”


Applying Larvicides

Larvicides can be applied to standing water as a liquid, granules, or briquets. The briquets, or dunks, are the most common form used.

Mosquito dunks:

  • Are environmentally safe and can be applied by hand, by dropping them in standing water
  • Slowly release a long-term larvicide at the water’s surface
  • Can kill mosquito larvae for 30 days or longer
  • Are especially effective for areas where it is difficult to drain standing water, such as puddles, ditches, ponds, or tree stumps
  • Should not be applied to drinking water reservoirs or drinking water receptacles
  • Can be purchased at most gardening, hardware, or home improvement stores

Please follow the directions on the package.


Download a printable version of this fact sheet here.
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250 William Howard Taft Road
2nd Floor, Cincinnati, OH 45219
Phone 513.946.7800 Fax 513.946.7890