Add one more item to the list of reasons you don't want to find a tick feasting on your blood. A new and rare tick-borne disease known as Heartland virus is being reported in northwestern Missouri after two cases have been documented in humans so far.

A study published in the American Journal of Tropical Medicine and Hygiene reports that the virus, first documented in two Missouri men in 2009, can be traced back to lone star ticks and that humans are at a likely risk of infection.

Heartland virus, also referred to as HRTV, causes fever, headaches and low white blood cell and platelet counts. The two men infected in 2009 lived 70 miles apart. Each required hospitalization for their symptoms.

To date, no other cases of Heartland virus have been reported and the two infected men have made a recovery. However, Missouri health officials and the U.S. Centers for Disease Control and Prevention (CDC), warn that more people could become infected.

"Ten samples of ticks tested positive for the Heartland virus, nine of which were collected from the property of one of the patients and one that came from conservation lands nearby," said lead study author Harry Savage, PhD, a research entomologist at the CDC in Fort Collins, Colo.

"It's pretty strong evidence that the virus is persisting from season to season in tick populations and that these ticks play an important role in disease transmission."

Perhaps most famously, ticks are the transmitters of Lyme disease. But the arachnids can also transmit ehrlichiosis and Rocky Mountain spotted fever, among other conditions. HRTV is notably different from other tick-borne illnesses because it is a virus and therefore not responsive to antibiotics.

A doctor at the hospital where the two men were hospitalized discovered the virus after sending blood samples to the CDC for testing. All involved expected the results to be ehrlichiosis, as the tick-borne disease is common in the area where the men were hospitalized. Instead, the test revealed a previously unidentified virus.

Continued analysis of the virus revealed it is a type of phleboviruses, which can be carried by sandflies, mosquitoes or ticks.

Savage's study of HRTV is ticks resulted in the collection of 56,428 ticks from April to August of 2012. During the study period the virus infection rate in nymph stage ticks from one farm owned by a patient was about one in 500 over the study period.

HRTV is currently only documented in lone star ticks. Other tick varieties have not been shown to carry the virus.

The severity and prominence of HRTV infections in humans is unclear, as only two cases in humans have been reported.

"If these two cases represent the severe end, then there may be many other milder cases that are going undiagnosed," Dr. Lucas Blanton, an instructor at University of Texas Medical Branch at Galveston, told HealthDay.

"Until more patients are studied, I do not think we know the full implications of this virus."

Nothing other than the usual warnings about tick-borne illness prevention have been issued.

Still, "there's another tick-borne pathogen out there to be careful of," Savage told HealthDay.

To prevent Heartland virus and other diseases spread by ticks, the CDC recommends taking the following steps:

  • Wear repellent

  • Check for ticks daily

  • Shower soon after being outdoors

  • Call your doctor if you get a fever or rash