After a storm passes and its floodwaters subside, a pestilence of mosquitoes may begin.
The insects thrive in wet environments, with some species laying their eggs in moist soil or above water lines in containers of water.
According to the Centers for Disease Control, some of those "containers" include pet water bowls, buckets, pool covers, trash cans, tree holes shaped in a way that can collect rainwater, irrigated fields and floodplains by the banks of rivers and streams.
Mosquitoes that lay their eggs in habitats like these are referred to as floodwater mosquitoes. These species lay their eggs to "dry out and then hatch when rain floods the soil or container", says the CDC. When dried out, the eggs can live for up to eight months; but once they become covered by water, they can hatch and grow into adults in about a week.
This is why mosquitoes appear in greater numbers after a flood.
Why mosquitoes are dangerous
It’s important to be aware of the rise in mosquito numbers after a storm because mosquitoes can be carriers, or "vectors", of diseases.
Thankfully, most of floodwater mosquitoes — also known as "nuisance mosquitoes" — generally "do not spread viruses that make people sick," according to the CDC.
However, increased rainfall can lead to mosquitoes spreading infections in areas (particularly outside of the continental United States) already plagued by certain diseases. Examples of those diseases are:
- West Nile fever, mostly mild infection, but can be fatal for less than 1% of infected
- Zika, which causes birth defects such as underdevelopment of the brain
- Malaria, a potentially lethal disease that causes flu-like illness
- Lymphatic filariasis, a parasitic disease caused by microscopic worms
How to protect yourself from mosquitoes
After a flood, many people may spend an increased amount of time outside to clean up. That time outdoors increases their chances of being bitten by mosquitoes.
Mosquito bites often result in an allergic reaction, with bite areas becoming swollen, sore, red and itchy. People with more severe reactions may experience swollen lymph nodes, hives and a low-grade fever, says the CDC.
Measures can be taken to prevent or limit the number of mosquito bites you or your loved ones might experience:
- Wear EPA-registered insect repellents with active ingredients like DEET or oil of lemon eucalyptus
- Wear long pants and shirts with long sleeves (you can also treat your clothes with an insecticide)
- Use mosquito netting to cover baby carriers and strollers
How to control mosquito numbers
Because of the problems mosquitoes can cause, it’s critical to find ways to curb mosquito numbers.
While professionals can create mosquito control plans, homeowners can take small actions to help control mosquitoes, says the CDC:
- Remove standing water by turning over, covering or throwing out containers of water on a weekly basis, filling tree holes to keep water from filling them up, covering plumbing pipes or vents that might be open and repairing any cracks in septic tanks
- Kill mosquito eggs and larvae by treating large bodies of water (not used for drinking and can’t be covered or thrown out) with larvicide
- Kill adult mosquitoes outside by using insecticides
- Prevent mosquitoes from flying into your home by using air conditioning, if possible.
- If allowing air to flow into the home, be sure windows and doors are covered with unbroken or repaired screens.