A mosquito bite wasn't responsible for the West Nile virus infection that killed a Colorado cancer patient, the virus may have been transmitted through a screened blood transfusion.
This could be the first case of West Nile caused by an infected blood donation that originally tested negative during the screening process, ABC 7 via the Denver Channel reported.
Since donated blood is always tested for West Nile, only 12 blood transfusion related cases have been reported in the past 10 years, LiveScience reported.
The man who received the fatal transfusion had gotten a bone marrow transplant to treat non-Hodgkin's lymphoma.
The man started to experience symptoms, such as low blood pressure and an altered mental state, about 20 days after receiving blood transfusions as part of his treatment.
Experts ruled out the source of infection as mosquito bite, since the man had been hospitalized for a considerable amount of time.
Blood transfusions rarely come from a single source; they are often "pooled" from multiple donors. The blood combination given to the infected man tested positive for West Nile, but the six contributing samples each tested negative. Since individual testing is more accurate, the blood was deemed safe.
The researchers believe the concentration of West Nile in the blood was low, and that's why it did not show up on a blood test. The man's compromised immune system may explain why he was unable to fight off the infection.
The laboratory that screened the infected blood has adopted a new policy to dispose of all samples that tests positive for West Nile, even if the individual samples come up negative.
Symptoms of West Nile include: "headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis," the Centers for Disease Control and Prevention (CDC) reported.
The CDC noted people with prior conditions such as diabetes, hypertension, and cancer are at a higher risk of contracting the virus.
