This is Gwen Outen with the VOA Special English Health Report.

Blood transfusions can save lives. But they can also spreaddiseases. Researchers believe this is how at least two people inBritain became infected with the human version of mad cow disease.They say the cases appears to confirm that eating beef from aninfected cow is not the only way the disease can spread.

The first case was reported at the end of last year; the secondwas reported earlier this month in the magazine The Lancet. Thesecond patient had received a blood transfusion five years ago. Theunidentified person was one of seventeen known to have receivedblood from people who later developed vCJD. The full name is variantCreutzfeldt-Jakob disease.

The disease attacks the brain and central nervous system. But inthis patient, the infection had not spread to those areas. In fact,the report says the elderly person never developed signs of thedisease. The patient died of unrelated causes. Tests later found theinfection in the spleen.

Scientists say the finding suggests that a larger population ofpeople could become infected. And here is why:

The human genetic map comes in different versions calledgenotypes. This patient had the most common genotype in the Britishpopulation. One hundred fifty deaths from the human form of mad cowdisease have been reported worldwide. But so far, there have been nosuch cases in people with this common genotype.

James Ironside is an investigator with the CJD Surveillance Unitin Edinburgh. He says infections might take longer to appear inpeople with this genotype.

The evidence also suggests that people without signs of thedisease could still carry the infection. And they may be able topass it to others.

In cows, the official name of the disease is bovine spongiformencephalopathy. Holes form in the brain. Researchers say the diseaseis caused by prions, proteins that are deformed and infectious. Nocure is known. But French scientists reported in The Lancet thatthey have identified a new way to clean prions off of medicaldevices.

Also, American scientists reported on a method used in Britain totry to make blood safer for transfusion. White blood cells areremoved to lower the risk of the human form of mad cow disease. Butthe researchers say animal tests found that the risk is reduced byonly about forty percent.

This VOA Special English Health Report was written by CynthiaKirk. This is Gwen Outen.