West Nile Virus Risk Level and Surveillance Results


Week Ending October 27, 2018 (MMWR Week 43)

West Nile  virus Transmission Risk Level* by Region

Key to West Nile Virus Risk Levels

Ket to West Nile Virus Risk Levels

West Nile virus is the most common mosquito-borne disease in Kansas and the United States. Several species of mosquitoes are responsible for transmission of arboviruses but Culex species are the primary vector for West Nile virus in Kansas and the United States. In 2017 the Kansas Department of Health and Environment, with funding from the Centers of Disease Control and Prevention, expanded the mosquito surveillance from 1 to 3 counties (Reno, Sedgwick, and Shawnee). These counties will continue to participate in surveillance in 2018. In addition, we collect mosquito surveillance data from 3 additional partners throughout the state. Mosquito surveillance began on May 13, 2018 and will continue through mid-October 2018.

The risk of acquiring WNV infection depends on various factors including time of year, number and location of infected Culex species of mosquitoes, and the number of days with sufficient heat. Warm temperatures increase the rate of mosquito larvae development which increases the mosquito population size.The risk of WNV transmission is lower in the spring but rises through the early and midsummer months and usually reaches peak transmission during July, August, and September.

In 2018, WNV risk levels have been developed for Kansas based on the following criteria:

  • Presence and abundance of Culex spp. of mosquitoes.
  • Average temperature for the previous two weeks.
  • Historical data indicators for the weeks of increased WNV human cases.

Regardless of the West Nile virus risk level for your area, there is no such thing as being 'risk-free'. Take precautions when you are out in areas where mosquitoes are present.

Highlights this week:

  • Northwest: Low risk due to decrease in two week average temperature and lower Culex species mosquito abundance than the same week in 2017
  • North Central: Low risk due to decrease in two week average temperature and lower Culex species mosquito abundance than the same week in 2017
  • Northeast: Low risk due to decrease in two week average temperature and lower Culex species mosquito abundance than the same week in 2017
  • Southwest: Low risk due to decrease in two week average temperature and lower Culex species mosquito abundance than the same week in 2017
  • South Central: Low risk due to decrease in two week average temperature and lower Culex species mosquito abundance than the same week in 2017
  • Southeast: Low risk due to decrease in two week average temperature and lower Culex species mosquito abundance than the same week in 2017

Methods for Risk Assessment
We utilize three factors in our risk assessment model; temperature, mosquito surveillance data, and human cases of WNV. Each factor has set benchmarks and each benchmark is assigned a value. The values from these three categories are averaged. The average rating is assigned a WNV risk level for each week. The three factors are as follows:

  • High-risk environmental conditions include above-normal temperatures with or without above-normal rainfall. We use the average daily temperature during the prior 2 weeks as our benchmark.
  • Culex species of mosquitoes serve as the main source of WNV transmission to people and horses. Relative abundance of Culex species mosquitoes compared to the same week in the previous year are compared.
  • Number of human cases of WNV each week based on the average number of cases in the previous five years.

For WNV human case counts updated weekly, visit
http://www.kdheks.gov/epi/case_reports_by_county.htm.

For more information on arboviral disease surveillance in Kansas call the Kansas Department of Health and Environment’s Infectious Disease Epidemiology and Response section at (877) 427-7317 or email at kdhe.epihotline@ks.gov.

Archived West Nile Virus Risk Weekly Reports

Zika Virus Surveillance

Zika virus disease is caused by the Zika virus, which is spread to people primarily through the bite of an infected Aedes species mosquito. The most common symptoms of Zika are fever, rash, joint pain, and conjunctivitis (red eyes). The illness is usually mild with symptoms lasting for several days to a week after being bitten by an infected mosquito. Zika virus infection during pregnancy can cause serious birth defects including microcephaly. Zika virus can also be spread through sexual contact.

There has be no local transmission of Zika virus in Kansas.

The two mosquitoes that can spread Zika virus are Aedes albopictus and Aedes aegypti; both are non-native invasive mosquito species in Kansas.

Learn more about Zika virus at http://www.cdc.gov/zika/index.html.

Mosquito Bite Prevention

Avoid mosquito bites by following the three Ds:

  • DRAIN – eliminate standing water where mosquitoes live and breed
    • Empty standing water from tarps, old tires, buckets, and other places where rainwater collects. Use larvicide in low-lying areas where water cannot be removed.
    • Refresh water for bird baths, pet bowls, and wading pools at least every three days.
  • DRESS – cover your skin with clothing when outdoors
    • Wear protective clothing when practical (long sleeves and pants).
    • Limit outdoor activities when mosquitoes are most active.
  • DEET – use insect repellents that contact DEET or other EPA-approved repellents
    • When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women.

Reports:

Additional Resources:

Kansas Biological Survey –
               http://kbs.ku.edu/

Centers for Disease Control and Prevention –
               Arbonet Maps - http://www.cdc.gov/ncidod/dvbid/westnile/usgs_frame.html
               La Crosse encephalitis - http://www.cdc.gov/lac/
               St. Louis encephalitis - http://www.cdc.gov/sle/
               West Nile virus -http://www.cdc.gov/ncidod/dvbid/westnile/index.htm
               Zika virus - http://www.cdc.gov/zika/index.html

Kansas State University College of Veterinary Medicine –
               Information about West Nile virus in horses - https://www.vet.k-state.edu/vhc/services/equine/internal-medicine/west-nile.html

Kansas Department of Health and Environment –
               Information on number of cases of any reportable disease - http://www.kdheks.gov/epi/annual_summary.htm

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