ABOUT two per cent of blood collected from donors is thrown away each year because it is contaminated, mostly with the Hepatitis B virus.

But the probability of a person being infected with Hepatitis B and C or even the Aids virus from blood transfusions is extremely low, due to the stringent and comprehensive screening for infectious diseases, said a spokesman for the Bloodbank.

Hepatitis B is a serious viral infection which is transmitted through semen, vaginal secretions, saliva, open wounds, breast milk as well as through blood.

The chances of catching it from donated blood are higher than with Hepatitis C and HIV because it is more prevalent, said the spokesman.

Each year, between 53,000 and 60,000 units of blood are used. A unit is 430 ml.

The Bloodbank, which is based at the headquarters of the Health Sciences Authority at 11 Outram Road, could not give ratios for the likelihood of infection in Singapore.

Earlier this month, electrician Neo Swee Chye, 30, was jailed for 15 months after donating HIV-infected blood. Luckily, no patient received it.

But Neo also gave blood on July 28, 1991 and Dec 12, 1999. On both occasions, he tested HIV negative. His blood from those two donations was given to four patients.

Three have tested HIV negative, while the first person to receive Neo's blood in 1991 has since died from a non-HIV-related infection.

In 1997, a HIV-infected blood donor who lied on his donor registration form on six different occasions was jailed 12 months. Two persons who received the man's blood contracted HIV.

The Ministry of Health told The Sunday Times that it could not comment on their current status because of patient confidentiality.

Blood donation is the only source of blood supply, especially in emergencies, but for patients scheduled for surgery, autologous blood donation is a better option.

This is when people donate their own blood in advance of their operation.

About 1,800 autologous units of blood are collected each year. Patients take iron supplements one week before the first donation and for three months after the last donation.

Depending on how much blood they will need, it can be collected once every three days if their blood levels are acceptable and can be stored for up to five weeks.

Following the official launch of the National Blood Donor Recruitment Programme last weekend, more than 800 people have pledged to donate blood regularly.

But the figures are still disappointing to the Singapore Red Cross Society, which is now responsible for recruiting blood donors.

'As you can see, we still have a long way to go,' said a spokesman.

A Blood Donor Association will also be established following a suggestion by Mr Chan Soo Sen, Parliamentary Secretary (Prime Minister's Office and Ministry of Health).

A meeting will be held soon to discuss how it can be implemented.

People who wish to make a donation pledge can visit the newly-launched blood donation website Donorweb at donorweb.org.