A tick-borne infection known as Babesiosis, which can cause severe disease and even death, is becoming a growing threat to the U.S. blood supply, according to a study led by government researchers published Monday.

Babesia, a tickborne parasite of red blood cells, is being transmitted through blood transfusions, according to results of a collaborative study, led by the Centers for Disease Control and Prevention, which found that the parasitic infection may be increasing across the country since 1979, the year the first known case occurred.

A recent study led by Dr. Barbara Herwaldt of the CDC, published in the Annals of Internal Medicine, found cases had occurred year-round with data from the past three decades.

Babesia infections are marked by fever, chills and fatigue, but they can also cause organ failure and death, health officials said.

The rare disease is known to occur naturally in seven U.S. states - Massachusetts, New York, Connecticut, Minnesota, Rhode Island, New Jersey and Wisconsin - during the spring and summer seasons.

“We want clinicians to become more aware of babesiosis, including the small possibility of transmission via blood transfusion,” said Herwaldt, M.D., M.P.H., CDC medical epidemiologist. “If a patient develops unexplained fever or hemolytic anemia after a transfusion, babesiosis should be considered as a possible cause, regardless of the season or U.S. region.”

However, transfusion–associated cases of babesiosis have been identified in 19 states and have occurred year–round.

Of the 162 cases of Babesia infection caused by blood transfusions between 1979 and 2009, 77 percent occurred between 2000 and 2009, CDC officials said.

Babesia microti has become the most frequently reported transfusion-transmitted parasite in the United States, CDC researchers wrote, far outpacing malaria infections, which accounted for 49 cases of transfusion-associated disease during the same period, including just five cases during 2000-2009.

In a separate study, published on Monday in the journal Pediatrics by a team at the University of Nebraska, researchers looked at seven cases of transfusion-associated Babesiosis in premature infants.

They found blood transfusions from two infected units of blood caused all seven of the cases of Babesiosis, where symptoms of the infection varied widely, but babies with the lowest weights at birth were at greatest risk of serious infection.

The authors warned doctors in areas in which Babesiosis occurs to be watchful for cases in premature infants exposed to blood transfusions.

Our findings underscore the year-round vulnerability of the U.S. blood supply - especially, but not only - in and near Babesiosis-endemic areas.

The CDC researchers called for better ways to prevent and detect cases of transfusion-associated Babesiosis.

...They also highlight the importance of multi-agency collaborative efforts to detect, investigate, and document transfusion cases; to assess the risks for transfusion transmission; and, thereby, to inform the scope of prevention measures, health officials said.