Mysterious Virus That Killed a Farmer in Kansas Is Identified

Researchers have identified a previously unknown virus, thought to be transmitted by ticks or mosquitoes, that led to the death of a farmer in Kansas last summer.

The illness was fast-moving and severe, causing lung and kidney failure, and shock. The man, previously healthy, died after about only 10 days in the hospital, according to Dr. Dana Hawkinson, an infectious disease specialist who treated the patient at the University of Kansas Hospital in Kansas City.

The newly discovered microbe has been named the Bourbon virus, for the county where the patient lived, the Kansas Department of Health and Environment said in a statement released Monday. The virus was identified by scientists at the federal Centers for Disease Control and Preventionthrough a process that took several months, according to Dr. J. Erin Staples, a medical epidemiologist at the C.D.C. laboratory in Fort Collins, Colo.

She said the virus was a type of thogotovirus, part of a larger family known as orthomyxoviruses. Its nearest relatives are found in Eastern Europe, Africa and Asia, Dr. Hawkinson said. Those viruses are spread by ticks and mosquitoes.

Researchers do not yet know whether there have been other cases in the United States. They hope to test stored blood samples from people who had similar illnesses in the past that could not be identified.

“I think we have to assume this has been around for some time, and we haven’t been able to diagnose it,” Dr. Hawkinson said. He added, “We suspect there have been milder cases and people have recovered from them, but we don’t have a lot of information.”

There is no treatment for the disease. The best defense is to avoid insect bites by wearing pants and long sleeves outdoors and applying bug spray that contains the repellent DEET.

The medical mystery began late last spring, when the patient was admitted to the hospital with a high fever, muscle aches and loss of appetite. He worked outdoors and often had tick bites. That history and his symptoms, combined with abnormal results on blood tests — his liver enzymes were too high, his platelets and white cells too low — made doctors suspect tick-borne diseases like Rocky Mountain spotted fever or ehrlichiosis. But tests for those illnesses came back negative.

Dr. Hawkinson suspected another, recently discovered tick-borne illness caused by the Heartland virus and sent blood samples to the C.D.C. for testing. But those tests also came back negative.

Researchers at the C.D.C. noticed that something else seemed to be growing in the samples that were tested for the Heartland virus, and they eventually identified the Bourbon virus.

But the researchers are not certain that ticks or mosquitoes transmit the virus, or whether other animals might carry it.

“We will be working with state and local health departments come springtime to do extensive field investigations,” Dr. Staples said.

For now, the risk to the public is low because ticks and mosquitoes are not active in cold weather. But ticks rebound earlier in the year than mosquitoes do, she said, once the temperature starts consistently reaching 55 degrees Fahrenheit.