The hospital is still investigating the source of infection, which could be linked to contaminated prepacked food such as bread or biscuits. The fungus is harmless to people with normal immunity but could be fatal to those with depressed immune systems.

The five patients have been put on a drug called posaconazole, the only treatment for the infection. The hospital has only a small stock of free samples of the drug.

The hospital decided on Wednesday to suspend its bone marrow transplant services for a week until it could get supplies of the drug from overseas.

Mr Chui said the bone marrow transplant unit started using the drug in mid-January and formally asked the pharmacy department to buy the medicine on Monday - only for one patient.

'We did not know that several other patients have also been put on the medication until the Wednesday press conference,' he said. 'We hope there is better communication in the future so medical services will not be affected because of a shortage of medicine.'

The pharmacy department yesterday also issued an internal memo to remind doctors to dispense all medicine through pharmacists. Mr Chui said posaconazole had been directly dispensed by hospital doctors to patients. 'We understand that some doctors may not be able to follow the strict guidelines during an emergency situation,' he said. 'If the drug is dispensed by us, we can better monitor the demand.'

The head of the University of Hong Kong's bone marrow transplant unit, Raymond Liang Hin-suen, said yesterday suspension of its programme was not solely the result of the shortage of the drug.

'A shortage of medicine is not the only reason we have to suspend,' he said. 'We also have to make sure all patients who come to our unit are safe and we have to test their stool samples before conducting a bone marrow transplant on them. That is why we have to postpone two to three transplants for a week.'

The outbreak began in November, when a six-year-old boy with leukaemia died 23 days after developing a distended abdomen. Last month, an 11-year-old boy with leukaemia developed gangrenous appendicitis due to the disease. On Wednesday, a 38-year-old man, also a leukaemia patient, was diagnosed with gangrenous appendicitis. Three suspected cases have also been identified.

'All the cases came very suddenly. We have taken immediate action,' Professor Liang said. 'We do not stock up on a large amount of medicines because there could be a waste of money if they are left unused. This medicine is very expensive.'

He said a batch of medicine from Australia would arrive in a day or two and he was confident transplants could be resumed within a week. The Hospital Authority said it would step up infection control at hospitals and would advise patients on food safety.

A spokesman for the Centre for Food Safety said it had not yet received food samples for tests and that the Centre for Health Protection had launched an investigation, on which the two centres would work together.

Foreign invasion

Mucormycosis is caused by the mucorales fungi. The aggressive, opportunistic infection was first described in 1885

1 The fungi spores (above) ? which are everywhere ? enter body through mouth and nose

2 Spores germinate in nose and throat

3 Fungus then directly invades blood vessels. Infection most commonly affects nose, sinuses, eyes and brain

4 Less commonly, infection occurs in gastrointestinal tract

Infected and dead tissue must be removed, but even with surgery and antifungal drugs, many patients

die

SOURCE: EMEDICINE