'All these 10 hours I had to carry her in my arms. I don't know how I shall keep doing this duty [of taking care of my sister], in the absence of my mother.'

Their mother was killed in politically related violence last month, and their father, Sankha Sardar, works for daily wages as an ambulance driver.

But as difficult as Rimi's and Raju's lives are now, an even darker shadow hangs over the family.

Three years ago, Rimi was infected with HIV and hepatitis B after a transfusion with blood supplied by Calcutta's largest government blood bank.

Tragically, her case is far from unique. According to data released by the Thalassaemia and Aids Prevention Society, she is one of at least 300 children it suspects were infected with HIV in the past four years after receiving tainted transfusions at government facilities.

The society, which says it conducted an exhaustive year-long survey, found that most families with infected children were not making the HIV status of their children public, fearing discrimination.

'Although it is certain that the children got the infection through tainted blood, the families of the victims in most cases do not want to accuse the government blood banks for the infection because they need their [blood-bank officials'] co-operation for future supply of blood for their children,' Sailen Ghosh, society secretary, said. In addition, the children face ill-treatment if their status does become known.

The society said that last year, staff of a government hospital refused to conduct vital surgery on thalassaemic child Maniur Rahman, who was infected with HIV via transfusion. However, the surgery was finally conducted after human-rights campaigners held a statewide demonstration.

Rimi's father, for one, is refusing to accept his daughter's fate quietly, taking her case to West Bengal state's Human Rights Commission. He is demanding that officials at least investigate how Rimi became infected and take measures to minimise risks.

The Human Rights Commission is investigating the case, and may take one to two years to reach a finding. Because of the commission's investigation, blood-bank authorities are not willing to discuss the case with the media. But they appear to be under pressure and accept that they were at fault.

Prasun Bhattacharya, a senior administrative officer of Calcutta's Central Blood Bank, which allegedly supplied the tainted blood to Rimi, visited her parents last year and urged them not to make any move against the blood bank.

'He begged forgiveness on behalf of the blood bank for infecting my daughter with fatal diseases,' Mr Sardar said.

The Health Ministry of West Bengal state - of which Calcutta is the capital - has refused to comment on the case, citing the Human Rights Commission's investigation.

'Compared with the private ones, government blood banks have a worse track record of infection,' said Ashok Ghosh, an Aids activist based in Calcutta.

'Poorer families come to government banks, where blood is cheaper or free. Most of the children who get the fatal infections are from poorer families, and they all are suffering.'

An investigator with the commission, who reviewed Rimi's case history, said it was easy to prove that Calcutta's Central Blood Bank was at fault. 'The infections of Rimi and other children with hepatitis B prove that the screening cell of the blood bank did not do their job properly and endangered children's lives,' said the investigator, who is also a senior police officer.

Meanwhile, the society is trying to persuade families suffering a similar plight to launch a national campaign to force the government to revamp the monitoring system in blood banks. The current screening method for HIV in donated blood at Indian facilities, the so-called Elisa test, can fail to detect the virus in donors if they have only recently become infected. The society wants the screening replaced with the more comprehensive DNA PCR (polymerase chain reaction) method.

Persuading parents to go public has not been easy.

Pinagapani Manorama, a Chennai-based doctor working with HIV-positive children, said: 'By hiding the children's HIV status the parents are denying them vital anti-retroviral drugs, increasing their physical miseries and shortening their lives, which is foolish and unethical.'

Activists from groups including the society also want the government to take responsibility for the children's plight by paying compensation.

Rimi's father says no amount of compensation can make up for the knowledge that the viruses causing Aids and hepatitis B remain in Rimi's body. 'But I shall consider my step [to the Human Rights Commission] successful if it can trigger a movement that can ultimately save other thalassaemic children from being infected by blood banks in future.'