Health officials in Bangladesh fear that poor regulation of blood donations could lead to a big rise in HIV and hepatitis.
Most blood in the country is unscreened and much is donated by a small number of regular donors who are known to carry diseases.
A survey in one area showed that 29% of commercial blood donors carried hepatitis B, 3.8% carried hepatitis C and many others had syphilis.
Only the poor sell their blood and many are drug addicts who need the money to pay for their next fix.
Aid workers who hand out clean syringes to drug users to reduce the risk of transmitting infections estimate that one in five addicts sell their blood.
HIV increase
One doctor told the BBC that she feared the problem could lead to a big rise in HIV and hepatitis cases and present a serious danger to public health.
"A survey last year found that 20% of intravenous drug users were professional blood donors.
"They sell their blood to government hospital blood banks and to private banks to pay for their drugs. This is one way to transmit HIV."
Bangladesh has seen a massive increase in HIV cases in recent years.
The government is trying to persuade patients' relatives to give blood, but the backstreet trade in blood is booming because of legal loopholes.
Private blood banks are difficult to supervise and health workers say a more secure system is needed to ensure diseases are not spread.
Background Briefings
Medical notes
Drug-resistant HIV strains increasing
(23 Sep 99 | Aids)
Global race to curb Aids
(02 Jul 99 | Aids)
Aids worldwide
(07 Jul 99 | Aids)
Aids up close
(02 Jul 99 | Aids)
UNAIDS
World Health Organisation
Aids in Bangladesh
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