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Mosquito-borne encephalitis in the U. S. is prevalent in several forms and is geographically wide-spread. The Western Equine and St. Louis viral strains were the most common before the invasion of West Nile Virus.   West Nile Virus first showed up in Idaho in 2004 and in 2006 Idaho led the nation in reports of human illness associated with WNV with 996 cases being reported to the state health department. Encephalitis is an inflammation of the brain and central nervous system, and is characterized by a high to moderate mortality rate, with some survivors left with permanent physical and mental disabilities. Contact the Health department or you doctor for more information.

For More information visit http://www.cdc.gov/niosh/topics/outdoor/mosquito-borne/default.html

TFCPAD traps mosquitoes to test for virus through the county during the summer. Trapped mosquitoes are separated by species using a microscope. Some species are more prone to carry diseases than others and we try to focus our work more on them. Trapping of mosquitoes also allows us to monitor the effectiveness of our treatments and find additional areas in need of treatment.
Map of Idaho WNV: http://healthandwelfare.idaho.gov/Portals/0/Health/Epi/WNV/2016WNV%20case%20counts%208%201%202016.pdf?ver=2016-08-01-104144-107

May and June mosquito trapping reports low mosquito numbers.
July 31, no WNV found to date in Twin Falls County. Canyon County detected WNV on July 15th.
Aug 18, no WNV found to date in Twin Falls County. Elmore County detected WNV on August 12th.                                          
Sept 25, no WNV found to date in Twin Falls County. Owyhee County reported two human cases of WNV, and Gooding County reported one case of a horse contracting WNV, and a possible human case of WNV.

Mosquito trapping started in May. Mosquito trap counts have been low due to control and cooler temperatures this summer.

June 26 - One trap location North of Filer near the Jerome and Twin Falls County border tested positive for WNV.

August 16 - One trap located southwest of Filer in a rural area tested positive for WNV. We are finding an increase of mosquitoes from containers, buckets, and horse troughs as well as over irrigated pastures.

August 27 - A trap set northwest of Buhl along the river corridor tested positive for WNV.

May, start of mosquito trapping and WNV testingJuly 25, No WNV to date in Twin Falls County, however WNV is in the magic valley, Positive mosquitoes have been found in Gooding County.Aug 8 WNV positive mosquitoes were found in a trap North of Buhl along the river. (along Gooding / Twin Falls County line). Its been a hot sumer, We are finding mosquitoes in pastures that are over irrigated and water stands for longer than 5 days.

2017May 22 Mosquito trapping started
July 22 over 140 trap nights to date through out the county, and no WNV. We have also trapped in surrounding counties. WNV has been found in other parts of the state so it could arrive at any time. Please help reduce mosquito habitat.

Aug 12 Two trap locations held mosquitoes testing positive for WNV, both were near Twin Falls one near the snake river and one near Rock Creek

Aug 18 traps set in the vicinity of last weeks positive WNV near twin falls and the Snake River  once again found WNV positive mosquitoes, all other trap locations were negative.


Mosquito traps are set county wide on a rotational basis as part of our standard surveillance This year trapping started in April.

Sept. 30, Traps set few miles east of Twin Falls next to the river tested positive for WNV. Sites identified to contain mosquito larva treated and continual monitored.    

Sept. 15, One trap set near the town of Burger tested positive WNV. Identified the most likely site which was filled in to remove from possible future breading areas.

Aug 17, One trap set several miles to the South of Filer contained mosquitoes testing positive for WNV.

August 3 , One trap set near Twin Falls along the Snake River contained mosquitoes testing positive for WNV. Expanded treatment and surveillance will be conducted in this area. Please take steps to reduce mosquitoes by eliminating habitat and reducing exposure to mosquitoes. To date this year  over 140 locations in the county trapped for mosquitoes and over 100 mosquito pools have been tested for WNV.


Two traps set August 16 and retrieved August 17 contained mosquitoes that tested positive for WNV. Traps were set between Kimberly and Twin Falls. Expanded treatment and surveillance will be conducted in that area. Please keep in mind that WNV may be found anywhere in the Magic Valley. A horse was recently found with WNV in Gooding. We regularly inspect and treat for mosquitoes in Twin Falls County, but most surrounding counties do not conduct surveillance or mosquito control. 

Take the steps to reduce mosquito habitat by draining standing water and avoiding mosquitoes at dusk and dawn when they are most active.

Mosquito traps are set county wide on a rotational basis, some areas have had high numbers of flood water mosquitoes following the heavy spring rain. overall Culex numbers (species responsible for WNV are low)

July 30,All Tests from Twin Falls county still negative. However WNV has been found in Idaho so take precautions.

July 1,  all mosquitoes testing negative for WNV


October 11, 2014 End of mosquito trapping and testing for West Nile Virus, No new positive tests and low mosquito counts.

August 21, 4 new WNV positive locations . Four mosquito traps set between Buhl and Hagerman along the Twin Falls/Jerome and Twin Falls/Gooding county line tested positive for West Nile Virus this week.The 4 inches of rain from 2 weeks ago is resulting in some very high trap counts, mainly in floodwater nuisance species. People will really notice the nuisance species for the next 10 days or so. Culex numbers are still relatively low, but lots of container habitat so please dump it out! Previous Positive location tested negative this week.


August 13, Mosquitoes from location of WNV positive  from last week re tested positive again this week. Mosquito numbers at this location have declined by over 66%. Surrounding areas all tested negative. Please drain standing water in containers filled from all the rain!

August 6, First  mosquito pool testing positive for West Nile Virus , Trap was set in area between Twin Falls and Kimberly. All other traps have tested negative.

July 22, Mosquito count low.  No WNV detected in Twin Falls County.

June 16, Mosquito count low.  No WNV detected in Twin Falls County.


August 21, All mosquito pools tested negative this week.

August 14, Overall mosquito numbers and positives pools are declining.

Of the 3 locations that tested positive last week. 2 retested positive this week, along with a new location. 
Retesting locations from last week.

Trap # 201-13  ( Set along river near Jerome/ TF County Border)

Trap # 202-13  ( Set about 2 miles away from the Snake River and about 4 miles NW of Buhl)

New location,

Trap # 205-13 ( Set about 4miles away from the Snake River along Rock Creek near Twin Falls)

August 7, The expanded river corridor treatment is paying off, mosquito numbers are decreasing and only 2 of  the 6 locations retested as positive this week.  A new  location tested positive about 2 miles away from the river and about 4 miles NW of Buhl.
Please take the proper precautions as WNV is only as far away as a bird or mosquito can fly and just because it has not been found in your area doesn't mean its not there.

July 31, One of the sites that tested positive last week tested positive again this week.Over all mosquito numbers in this area are declining.

In addition  5 traps along the snake river corridor between Twin Falls and Gooding County tested positive for WNV.
(Positive mosquitoes were found in Gooding County this week as well.) Treatment and surveillance will be expanded in this area.

July 24, WNV found in mosquitoes trapped along the Snake River between Jerome and Twin Falls County.
Two Mosquito pools tested positive.  Surveillance and treatment of that area will be expanded. Take the proper precautions to avoid mosquitoes and eliminate their habitat.

July 17, No WNV in our traps, over 150 sites sampled to date, however WNV is endemic to Idaho and has been found in several places around the state. Recent hot weather has sped up the growth cycle, so watch out for standing water.

June 28, No WNV to date.

May 30, Trap counts low, No WNV detected. With recent rain don't forget to drain containers!

April 22, 2013 Weekly traping and testing of Mosquitoes is underway!


September 13, Trap counts for all species of mosquitoes were low. No Culex Tarsalis (our primary WNV carrier) were found in traps. All tests for WNV were negative.

September 6, Trap counts remain low, all tests for WNV were negative this week.

August 29, All traps this week have had low mosquito counts and tested negative for WNV! The cooler nights are slowing down the rate at which mosquitoes complete there life cycle. We are past the peak of summer mosquitoes numbers.

August 24, 10 traps were set August 20. One was a follow up to last week’s Buhl locations positive WNV finding.  It again contained a positive WNV mosquito. The good news is that total mosquitoes trapped at this location had declined by over 75 percent in the last 5 days. This area will continue to be monitored. In addition, a second positive mosquito pool was found west of Hansen near the South Hills. Once again this is a reminder that WNV is endemic to Idaho finding it is not a surprise. These findings help focus the work of the abatement district. If you live in are where it hasn’t been found yet, you still should take basic precautions to avoid mosquitoes and avoid creating mosquito habitat. 

August 17, During routine mosquito surveillance. A trap set Wednesday August 15 in a rural area West of Buhl contained Culex mosquitoes that tested positive for WNV. This was one of 18 traps set out this week.  All other traps tested negative.. Expanded surveillance and treatment of this area has been conducted. This finding is a reminder for people to take the proper precautions. 

August 8, No WNV found to date, Over 150 locations trapped with more than 5,000 mosquitoes put under the microscope to date. Please rember that  WNV is endemic to Idaho and even though we haven't found it yet residents still should take steps to elimate standing water!

July 11, Weekly mosquito trapping and survilance is underway, no WNV has been found to date.

Trapping and testing started in April, No WNV found as of June 6th Please report areas where you find mosquitoes!


10-28 Last trap date, No WNV found during season.

8-18 No WNV found in over 100 trap samples to date. High levels of nuicance mosquitoes found in some parts of the county, still need to treat drain or dump out standing water!

6-24 Weekly mosquito trapping and survilance is underway, no WNV has been found to date.

5-15 Start of mosquito trapping and disease survilance as permited by the weather.


Aug 24, Over 200 trap samples have been tested for WNV, none has been found to date. Trapping and testing will continue.

4-26 First traps set for mosquito survelance, trapping will continue every week during the summer.


Weekly trapping of mosquitoes in Twin Falls County started in May, Mosquitoes identified as the species Culex are tested for West Nile virus. 

8-25  First positive mosquito sample for West Nile Virus in Twin Falls County. Two mosquito traps near Buhl contained mosquitoes that tested positive for West Nile Virus. The TFCPAD is expanding surveillance and treatment in that area and encourages everyone to help eliminate mosquito habitat by draining standing water, and avoiding their bites through the use of repellents. 

9-1 Additional Positive Mosquito sample for West Nile Virus. One trap located 1 mile north of Filer tested positive. The trap only contained two mosquitoes! All additional samples from the area of earlier positives have been negative and subsequent traps set in the same location near filer failed to catch any mosquitoes. TFCPAD is continuing to treat for mosquitoes and encourages everyone to take the proper precautions!

 For more Information on West Nile virus please visit http://www.westnile.idaho.gov/!

Mosquito Identification