Significant rainfall events, such as hurricanes or tropical storms, can result in increased mosquito populations in the weeks after flooding. Large numbers of nuisance mosquitoes can hamper recovery efforts, but an increase in mosquito-borne diseases is not always expected.

For Mosquito Control Professionals:
The DPH has prepared guidance to help counties and municipalities apply for public assistance through the Federal Emergency Management Agency (FEMA), which can assist with expenses related to controlling mosquito population surges following a natural disaster such as a flood or hurricane.

Frequently Asked Questions

  • Adult mosquitoes do not generally survive high winds associated with a hurricane.
  • An increase in mosquito populations is expected in the weeks after flooding.
  • An increase in the number of people getting sick from diseases spread by mosquitoes, however, is not expected after flooding.
  • Flooding causes “floodwater mosquito” eggs, which were previously laid in moist soil, to hatch. The result is very large populations of floodwater mosquitoes, most of which are considered “nuisance mosquitoes.”
  • Nuisance mosquitoes do not typically spread viruses that make people sick.
  • Large numbers of nuisance mosquitoes can affect recovery efforts, and mosquito control experts often take steps to limit their numbers.
  • Rainfall can increase container-breeding mosquitoes that can spread diseases two weeks to two months after rains. Disease spread is not common after a hurricane, but is possible, especially in areas that received a lot of rainfall, but did not flood or have very high winds that would have dispersed mosquitoes and caused birds (virus reservoirs) to flee the area. So, cleaning up debris that may act as containers for mosquito breeding is still important, both from nuisance and disease points of view.

  • Conduct surveillance activities that include sustaining capabilities to capture occurrences of mosquito-borne diseases, perform epidemiological investigations, and test people, mosquitoes, birds, and veterinary animals for infection with mosquito-borne diseases. 
  • Provide recommendations consistent with Integrated Mosquito Management (IMM) guidance as established by the American Mosquito Control Association (AMCA).
  • Serve as ArboNet™ points of contact for South Carolina; enter all appropriate human and veterinary case data, as well as bird and mosquito surveillance data.
  • Provide guidance and technical support post emergency (hurricanes, tropical storms, etc.) to local government officials or local mosquito control agencies.

  • Provide guidance and resources to local authorities through collaboration with state emergency management, FEMA.
  • Provide technical guidance and expertise as requested by the State Emergency Operations Center.
  • Consult on specific and/or emerging issues with local programs through the State Emergency Operations Center.
     

DPH is not a resource for operational mosquito control supplies. We assist local programs to coordinate with external resources for mosquito control or surveillance

  • Establish baseline data for mosquito population density to verify the hazard.
  • Perform mosquito control and public education/outreach.
    • Determine mosquito population density and perform mosquito control and public outreach by using in-house equipment and staff, out-sourced services with neighboring municipalities, or a mosquito control contractor.

  • Adulticiding: The ground or aerial spraying of insecticides to kill adult mosquitoes.
  • Larviciding: The application of chemicals, including methoprene or Bacillus thuringiensis israelensis (Bti), by ground or air to kill mosquito larvae or pupae.
  • Breeding habitat removal or alteration (source reduction): The modification of potential breeding habitat to make it unsuitable for mosquito breeding or to facilitate larval control, including:
    1. Draining or removing standing water in close proximity to homes, schools, sheltering facilities, and businesses;
    2. Increased de-watering through pumping of existing drainage systems;
    3. Dissemination of information (e.g., inserting flyers with residents’ water bills, public service announcements, newspaper campaigns) to direct residents to remove mosquito breeding habitats.
  • For a list of complete mosquito abatement measures, consult Best Practices For Integrated Mosquito Management, published by the American Mosquito Control Association.