SOUTH DAKOTA (SDNW)– A South Dakota county with the second-highest national rate of lethal West Nile virus in humans shares a border with a county that has never reported a single case.

Between 1999 and 2023, Dewey County recorded 13.74 neuroinvasive cases per 100,000 people, just behind King County in Texas, according to the U.S. Centers for Disease Control and Prevention. Neuroinvasive refers to those more serious cases that can affect the brain and can be deadly.

Ziebach County, which borders the western boundary of Dewey County in north-central South Dakota, shows zero neuroinvasive West Nile virus cases, according to the CDC. The Cheyenne River Indian Reservation covers most of both counties. 

“That’s wild,” Randolph Runs After, environmental health specialist at Cheyenne River Sioux Tribe, said after learning about the Dewey County ranking. “We actually haven’t had that many cases in the last few years.”

The data aren’t wrong but needs explaining.

“The medical facility for both counties is in Eagle Butte, Dewey County, and they are the ones who report to the health department,” said Michael Claymore, director of the Cheyenne River Sioux Tribe Prairie Management Program.

Population numbers also impact incidence rates, Tia Kafka, marketing and outreach director at the South Dakota Department of Health, said in an email. The fewer residents live in a county, the more impact a single West Nile virus cases will have, she said.

“Historically, Brown County has been the hotspot for West Nile virus activity in South Dakota, with the most cumulative West Nile virus cases reported,” Kafka said.

Brown County, whose county seat is Aberdeen, recorded more than 340 West Nile virus cases between 1999 and 2023, which ranks it 24th among other counties in the United States, the CDC said. Within South Dakota, Brown County is followed by Pennington County, with more than 220 West Nile virus cases during that time, and Minnehaha County, with almost 200 incidents.

The U.S. Department of Health and Human Services defines a high incidence rate as one that is greater than 1.1 per 100,000 people. Analysis of the CDC’s historic data within this framework showed that 61 out of 66 South Dakota counties – which amounts to 92% – have a high incidence of West Nile virus cases in humans.

When bitten by a West Nile virus-carrying mosquito, most people will not show any symptoms, said Erin Staples, M.D., medical epidemiologist with CDC’s Division of Vector-Borne Diseases. Some will develop West Nile fever, but even fewer will get a neuroinvasive West Nile virus disease, which affects the brain or the space around it. Non-neuroinvasive cases are generally less serious. 

Virus reached SD in 2002, has been declining

Runs After remembers the first years of West Nile virus in South Dakota when “you could find dead birds here and there.”

The first reported case was in 2002 in a crow in Aberdeen, according to a Rapid City Journal story from July 2002. 

West Nile virus first appeared in the United States in New York City in 1999 and reached the West Coast by 2004, Staples said. She added that a lot of people got infected at the time because “there was no immunity in anybody.”

Since 2002, the South Dakota Department of Health has recorded more than 2,800 human cases, 53 of which were fatal.

In 2003, Virgil Christensen, an 89-year-old man from Wakonda in Clay County, became the first South Dakotan to die from West Nile, according to the Vermillion Plain Talk. 

Both South Dakota and the United States observed a peak in the number of West Nile cases that year. The state Department of Health recorded 1,039 occurrences.

This year, the South Dakota Department of Health has already recorded the first West Nile virus case of 2024.

The department’s West Nile Virus Surveillance tool shows that this non-neuroinvasive case of West Nile virus disease was found in a resident of Beadle County who is at least 64 years old.

The CDC’s surveillance tool shows that neighboring North Dakota and Nebraska have already recorded one and four cases, respectively.

Weather and human activity increase mosquito numbers

As of July 17, the South Dakota Department of Health predicted 48 West Nile virus cases for 2024 in the state.

Kafka said the state health department uses a model, updated weekly, that considers factors like historical human West Nile virus case data, environmental data, and current year mosquito pool testing data. 

Historically, late July and August tend to accumulate the highest number of West Nile virus cases across the United States.

South Dakota experiences the same trend because of “several interrelated factors,” Kafka said.

Mosquitoes that can transmit West Nile virus reach their highest population numbers during the warm summer. In addition, heavy rains create puddles and stagnant bodies of water, which are favorable conditions for mosquitoes.

“Warmer temperatures not only support mosquito breeding but also accelerate the development of the virus within mosquitoes, enhancing the risk of transmission to humans,” Kafka said.

People also like to spend more time outdoors during the summer, camping, hiking, and participating in evening gatherings, which increases their chances of encounters with mosquitoes, she said.

Mosquitoes are ‘the main culprit’

Staples, of the CDC, said West Nile virus is usually transmitted through a mosquito bite.

When bitten by a West Nile virus-carrying mosquito, some people will not exhibit any symptoms at all, she said. One in 5 will develop a febrile illness, which may involve getting a fever, a rash, a headache, muscle pain or joint pain. This is also referred to as West Nile fever. 

Some people will go on to develop a West Nile neuroinvasive disease. This can lead to encephalitis, which is inflammation of the brain, or meningitis, which is inflammation of the tissues around the brain and spinal cord, Staples said.

“Mosquitoes are often referred to as the deadliest animal in the world, as they cause more death and disease than any other animal on the planet,” Staples said.

Birds also contribute to the spread of West Nile virus. Once infected, they can develop enough virus to pass it on to a non-infected mosquito, which is why they are sometimes called “amplifying hosts,” she said.

Humans do not have the same capabilities, although they can spread the virus to one another through blood transfusion, Staples said.

Several vaccines have gone through the early stages of clinical development but are currently stuck at the part called efficacy trial, she said.

“You need to be able to say, ‘Where is there West Nile? I’m gonna start vaccinating people and look to make sure that the vaccine is very effective and can prevent infection,’ Staples said. “Unfortunately, we haven’t been able to necessarily predict where West Nile is going to occur. That’s really the sporadic and unpredictable nature of West Nile virus.”

CDC and state fund mosquito control

The South Dakota Department of Health received almost $1.5 million in 2023 for the department’s West Nile virus media campaign and laboratory testing of mosquito pools through the CDC’s Epidemiology and Laboratory Capacity Program.

This year, the state Department of Health allocated $500,000 in grant funds to distribute among cities, counties and tribes for mosquito control in amounts ranging from $500 to $20,000. Kafka said that 166 applicants received money based on the population and history of human cases. 

The Cheyenne River Sioux Tribe Prairie Management Program received $9,325 as part of the grant.

Claymore said the Prairie Management Program tries to eradicate mosquitoes in several different ways. He said the team monitors traps and tests captured mosquitoes to see if any of them carry viruses.

The program also conducts larva sightings, which involve putting chemicals in standing water to kill mosquitoes before they get a chance to develop into adults.

Workers also spray the ground, fog the trees and disperse microscopic droplets of a chemical compound mixed with oil through aerial fogging.

Claymore said the program uses all of the Department of Health grant money to buy just enough chemicals to last a season.

“I tell people to just watch the news and see where the mosquitoes are at, and they are moving towards us,” Claymore said. “Now it’s really important to be more vigilant with your personal protection.”

Mosquitoes in Sioux Falls ‘as bad as ever’

The city of Sioux Falls, Aberdeen and Pennington County, received $20,000 each.

Dominic Miller, environmental health manager for the Sioux Falls Department of Health, said in an email the city’s mosquito control program was created the same year the city recorded its first West Nile virus case, 2003. Now that over 20 years have passed, the number of mosquitoes in 2024 is “as bad as (the city has) ever seen it,” he said.

The city of Sioux Falls is divided into 18 spraying zones, and each zone has at least one mosquito trap. Every morning during weekdays, the mosquito control team checks all traps to count and test captured mosquitoes.

This summer, one of the traps collected 6,300 mosquitoes overnight, Miller said.

The mosquito control team uses the number of trapped mosquitoes to determine what zones to spray and aims to eradicate all kinds of mosquitoes, not just those that may carry West Nile virus, he said. 

Ways to prevent infection

Kafka said homeowners can minimize the risk of being bitten by installing or repairing window and door screens to keep mosquitoes outside of homes.

The state Department of Health also encourages people to reduce the risk of being bitten by mosquitoes and contracting West Nile virus by joining “the S.W.A.T. team:” 

• Spray: When outdoors, apply mosquito repellents that contain compounds like DEET, picaridin, 2-undecanone, param-menthane-diol, IR3535 or oil of lemon eucalyptus. 
• Water: Remove standing water from old tires, buckets and other containers that can give mosquitoes a place to breed; regularly change the water in bird baths and pet dishes, and stay away from areas near standing water.
• Arms: Wear pants and long-sleeved shirts to cover exposed skin. 
• Time: Limit time outdoors at dawn and from dusk until midnight when mosquitoes are most active

Susan Hoover, M.D., an infectious disease physician at Sanford Health, said that since there is no treatment for West Nile virus, it’s paramount to take those precautions.

If a person is bitten and exhibits such symptoms as fever, vomiting, diarrhea, headache or body aches and suspects they may have West Nile virus infection, they should contact their health care provider, she said.

The South Dakota Department of Veterans Affairs is honoring three of Bristol’s heroes in August. During World War II, three brothers from the Bristol area died in uniform while serving the U.S.

The department will be hosting a State Bridge Dedication Ceremony to honor three brothers, U.S. Navy Radio Man Second Class Ordien F. Herr, Naval Air Force Lieutenant LeRoy M. Herr, and U.S. Navy Radio Man Second Class Eugene L. Herr.

The ceremony will take place at 1:30 p.m., Aug. 5 at the high school gym in Bristol.

The US 12 Westbound bridge over the railroad, three miles west of Groton will be dedicated to RM2, LT, and RM2 Herr.

Eugene Herr was first reported as missing in action when he was serving on the USS Johnston, which was sunk at the Battle of Samar. He survived the sinking, but died two days later, Oct. 25, 1944, from exhaustion and exposure.

Having completed more than 38 missions during the war, LeRoy Herr’s PV1 Ventura bomber crashed while flying over Catalina Island Sept. 25, 1945.

On June 8, 1943, a transport carrying personnel to Sydney, Australia crashed leaving Tontouta Airfield, New Caledonia. Approximately three minutes after takeoff, the plane was seen going into a low turn and disappeared from sight. During the initial climb, one of the engines failed. The pilot tried to return to the airfield, but the aircraft stalled and crashed. The wreckage of the plane was in the water of St. Vincent’s Bay about 100 yards from shore. A total of 24 men were killed, one of which was Ordien Herr.

Naming bridges in honor of South Dakota’s combat veterans who died while serving their country is an initiative of Gov. Kristi Noem and the South Dakota Departments of Military, Transportation, and Veterans Affairs.

“Our fallen heroes are no longer with us, but their memories live on in the hearts of their loved ones and our state,” said Greg Whitlock, secretary of the South Dakota Department of Veterans Affairs in a release.  “Naming our South Dakota bridges in honor of our fallen gives us the opportunity for remembrance, reflection, and respect.  It helps us to honor the men and women who gave their lives in service to this nation. They cherished liberty and loved freedom so much, they were willing to lay down their lives to preserve our way of life.”

“We can never underestimate, or over appreciate, the costs they bore for us,” said Whitlock. “We must never forget that our fallen sacrificed their future and their dreams.  Their memories can only live through the accomplishments to present and future generations.”

Damages remain visible in the McCook Lake community on July 3, 2024, after a massive flood hit the area on June 23. (Joshua Haiar/South Dakota Searchlight)

When a record-high surge of water flowed down the Big Sioux River toward the southeast corner of South Dakota last month, local and state authorities activated a flood mitigation plan from 1976.

It saved North Sioux City and Dakota Dunes from disaster. But their neighbors in McCook Lake suffered a graphic reminder of how different their community is today than it was 48 years ago.

“Back when there were a few little cabins on the lake that you could replace for $20 apiece, and now there are little McMansions,” said Jay Gilbertson, geologist and manager of the East Dakota Water Development District, based in Brookings. 

‘We have nothing’: Flood victims say government failures continue after botched flood warning

He said it’s time for an update.

“Most definitely. The idea that a plan drawn up back then would still be applied today is kind of silly.”

Utilizing the existing plan, local and state authorities plugged the area under an Interstate 29 overpass with a sandbag-and-clay levee, to tie in with permanent levees that protect North Sioux City. The system diverted water toward McCook Lake, as intended.

But there was more water than anybody had ever seen before. Instead of causing a manageable rise in the lake, floodwaters slammed into dozens of homes, destroying around 30 of them and carving giant gouges in the land on the lake’s north shore. Fortunately, nobody was killed.

Union County Emergency Management Director Jason Westcott said officials thought the plan would work as it had in the past. Now he says something needs to change.

“We’re having a bad flood every four or five years,” he said. “Our rivers are changing and us humans are doing something to them.”

Some researchers and scientists say the changes are due to a greater frequency of severe rainfall and shifts in land use. And they say mitigation plans have not kept up.

“There’s no question about it,” said Carter Johnson, distinguished professor emeritus of ecology at South Dakota State University. “Mitigation plans, building standards and regulations are based on the 20th century data, which made sense, but we’re changing.”

Mark Sweeney, an environmental science professor at the University of South Dakota, shares those concerns. 

“Flood mitigation plans should never be considered static,” Sweeney said. “River channels are in a constant state of change, meaning flood hazards are likely to change, especially over decades.”

The recent flooding began when three days of heavy rainfall inundated southeast South Dakota, southwest Minnesota and northwest Iowa. The McCook Lake community did not anticipate the volume of water that overwhelmed some of their homes on June 23, according to Dirk Lohry, president of the McCook Lake Association.

But in hindsight, the disaster looks like another step in a progression of more frequent, more severe floods affecting the area during the past 15 years.  

“I’m 1,000 years old,” Lohry said. “I have now lived through two once-every-500-year floods.”

A changing environment

Warning signs have been accumulating in recent years about changing river flows in eastern South Dakota.

A U.S. Geological Survey report found a 298% increase in streamflow for the James River near Scotland, for example. The report says increases are linked to higher precipitation, urban development, tile drains used under farm fields, and grassland-to-cropland conversion.

The report found “a hydrologically unique trend in the eastern Dakotas that is not being observed anywhere else in the conterminous United States.” 

“Specifically, streams in the eastern Dakotas have experienced the greatest increases in streamflow during the last 60 years in comparison to any other USGS gaged stream in the United States.”

When North Sioux City developed its flood mitigation plan almost five decades ago, the highest recorded flow rate of the Big Sioux River in the city was 77,500 cubic feet per second, according to a North Sioux City official who spoke during a July 1 city council meeting. The flow during the recent flooding overwhelmed stream gauges, reaching what some city officials estimated to be 170,000 cubic feet per second.

Severe floods across the Midwest are becoming more common, mostly due to a greater frequency of severe rainfall, said Jonathan Remo, a geologist at Southern Illinois University. He said the “once-every-500-year” title given to some floods is a probability based on historical data.

“But we’re now seeing an unprecedented frequency of major precipitation events,” Remo said. “Something has fundamentally changed, and it’s related, in part, to climate change.”

Around the globe, large amounts of heat-trapping greenhouse gases are being emitted into the atmosphere. Warmer air holds more moisture, which, when it condenses, results in more intense precipitation. 

The state climatologist at South Dakota State University, Laura Edwards, has been saying for years that South Dakota’s climate is becoming wetter during wet cycles and drier during dry cycles, translating to more severe droughts and floods.

Carter Johnson, also of SDSU, has studied climate change for decades and said, “We’re seeing changes at rates that have never been observed before.” 

He said South Dakota can fund better preparation and mitigation for natural disasters, or spend more on recovery.

“Taxpayers are paying for it either way,” he said. “Insurance rates will continue to go up, natural disasters will continue to happen, and emergency response and cleanup is not cheap.”

Land-use changes

USD’s Sweeney said climate change is the biggest concern for the future, but added that changes to the landscape, like urban sprawl, are also contributing to worsening floods. He said water that would normally soak into the ground like a sponge, slowing its flow rate, now hits asphalt and runs right off. 

“We have known for a long time that runoff from asphalt is faster than from grassland,” Sweeney said.

Drain tile — perforated pipe installed under cropland to drain excess moisture — is another factor. When drain tile systems are installed, water that would otherwise accumulate in a field before absorbing into the ground or evaporating is instead channeled into ditches, creeks and rivers.

“Personally, I think tile drains are a slow-motion experiment we are playing,” Sweeney said.

A 2014 study in Ohio found that tile drainage significantly contributed to the amount of water discharged in the watershed. In Iowa, 2016 research indicated that tile drainage significantly alters streamflow, contributing 30% more water to the observed streams during precipitation events.

Converting grasslands to cropland can also make flooding worse. 

Meghann Jarchow, a USD professor of sustainability and grassland specialist, referenced a study showing grassland holds more water than cropland, with or without cropland drainage systems. Prairies have a thick layer of plant material that soaks up rain, which leads to less water draining away.

“We’ve changed so many things in our environment,” she said. “Policies need to keep up.”

Between 2008 and 2016, nearly 5 million acres of grassland were converted to cropland across 12 Midwestern states – including South Dakota – primarily for corn and soybean production, according to a 2021 study. That’s the equivalent of about five Rhode Islands. 

Solutions

For the residents of McCook Lake, one priority is clear: They want assurance that their homes will not be “sacrificed” again.

“They’ve got to change that plan,” Dirk Lohry said.

McCook Lake residents called on North Sioux City officials to change the current mitigation plan during a July 1 meeting, suggesting a large ditch be built to direct water to nearby Mud Lake — which does not have a community surrounding it — rather than McCook Lake.

Jay Gilbertson thinks it’s time those “once-every-however-many years” estimates get updated, partly because of how those odds drive design standards for infrastructure like waste management systems and dams. 

“You might have to make a system able to handle a once every 50-year event based on historical records,” Gilbertson said. “But 50 might not be 50, it might be 30.”

He said those adjustments could help ensure dams and levees are being built for the environment of the 21st century and beyond, not the 20th. 

Federal agencies and state and local governments are all responsible for updating design standards to reflect current climate data.

Zoning laws could also be updated to illustrate flood zones more accurately, Gilbertson said, restricting development in high-risk areas, and ensuring adequate park and wetland space to help absorb floodwaters. 

In 2020, State Climatologist Laura Edwards wrote about increased flood risks in South Dakota, highlighting how many properties are at greater risk than currently indicated by Federal Emergency Management Agency (FEMA) flood plain maps. Multiple McCook Lake residents told South Dakota Searchlight they do not have flood insurance, because of the expense and because they’re not in an area designated by FEMA as requiring it.

Sweeney said the accuracy of flood plain maps is critical, as are local government decisions about what development, if any, is allowed.

“We will never be able to eliminate flood hazards as long as the government allows people to build in flood plains,” Sweeney said.