A previously unknown but "novel" virus unlike anything ever seen before by American doctors has killed a man in Kansas and is raising fears it might become a killer virus.

Scientists are now calling this new virus the "Bourbon virus" after the county in Kansas where the deceased first victim lived. This healthy man in his 50s had been bitten by ticks before he got sick.

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He was treated with drugs normally effective against tick-borne diseases such as Lyme disease, but progressively got worse and died 11 days after he first became ill. Failing to determine what exactly caused this man's death, local doctors turned to the U.S. Centers for Disease Control and Prevention (CDC).

Dr. Charles Hunt, Kansas state epidemiologist, passed the samples along to the CDC. After months of work the CDC announced a culprit.

"We were not looking for a new virus," said Hunt, who helped report on the new virus.

"We are surprised. We really don't know much about this virus. It's important to find out more from a public health perspective. It is possible that other persons have been infected with this and not known it?"

"It took months to find out this a novel virus that belonged to a genus of viruses called Thogotovirus," said CDC's Dr. Erin Staples to NBC News. "Thogotoviruses have been described throughout the world."

She noted, however, this virus rarely causes human disease. The closest relative to the virus ever seen in the U.S. was a sample found in a bird's nest in Aransas Bay, off the coast of Texas.

CDC said this is the first time such a virus has caused human illness in the U.S. It's only the eighth time a Thogotovirus has caused symptoms in a person worldwide. Viruses in this group have been linked to ticks and mosquitoes in Europe, Asia, and Africa.

Dr. Staples thinks the new virus may have occasionally infected people, but they never knew what they had. Scientists only recently have possessed the tools and facilities needed to make this kind of identification.

"I think it has probably been present for a while," Staples said.

She said people should not worry, but people should avoid ticks by wearing long sleeves and using insect repellant outside.