“Without those transfusions my wife would have died. So if there are no donors, where are people who need blood going to get it from?” the father-of-two says.

On a bed next to Yuen is fellow donor Eddy Kung Chi-ho. He’s donating for the 111th time and says he followed in his father’s footsteps.

“My father donated so for me it was a natural progression,” says the 32-year-old. “I also know that when I donate blood I am saving lives, so for me that is enough motivation.”

It’s a Friday afternoon and the sixth floor of the Red Cross’ shiny new West Kowloon Donor Centre is almost full with people giving blood – one donation can save three or more lives. The silence is broken only by the almost hypnotic hum of the machines.

Red Cross’ recruitment and publicity manager Henry Man says “today is a good day with many donors” but he warns inventories are at alarmingly low levels and hopes World Blood Donor Day on June 14, with this year’s motto “Blood connects us all”, will help raise awareness.

Man says the Red Cross needs an average of 1,100 donors a day – about a pint (450ml) of blood is taken from each donor – in order to provide adequate supply of blood to all the city’s hospitals. At the moment the average number of donors is between 800 to 900 daily.

Blood products are needed to treat patients who have surgery because of illness or accident. It’s also used by people with chronic diseases. Hongkonger Grace suffers from thalassemia, a genetic blood disorder whereby she can’t produce enough haemoglobin and requires three bags of blood every four weeks.

“There are many people like me who need blood to sustain their lives so I am so grateful to those who donate,” Grace says.

But not everyone can donate. People who display flu symptoms are ruled out, while about 10 per cent of new blood donors are unfit to donate due to a lack of haemoglobin – a protein in red blood cells that carries oxygen throughout the body – caused by poor eating and living habits. Low blood pressure is another reason and SCMP photographer Nora Tam, who shot the photos for this story, was refused “because my veins are not prominent enough.”

Also at the centre is Cecilie Larsen. A regular blood donor in her home country Denmark, Larsen wanted to do her civic duty and donate in her adopted Hong Kong. However she was shocked to hear she was unable to give blood because of fears of Variant Creutzfeldt-Jakob disease (vCJD), the human form of mad cow disease.

“I went through two steps: filled out the forms and had a blood sample taken. But on the third step – the interview with a nurse – I was told I couldn’t continue because I’ve been in Europe more than five years after 1980,” says the 30-year-old.

According to the Hong Kong Red Cross donor selection guidelines, anyone who spent three or more months in Britain from 1980 to 1996, or five or more years in Europe from 1980 to the present, are unable to donate blood in Hong Kong due to fears of transmitting vCJD. This rule is based on evidence from a small number of case reports involving patients and laboratory animal studies that vCJD can be transmitted through transfusion.

Similar measures apply in other countries including the US, Australia, New Zealand, Japan and Singapore.

According to the Hong Kong Department of Health, two cases of vCJD have been recorded in Hong Kong since 2001, one of them fatal and both classified as imported cases from Britain.

The first case in 2001 involved a 34-year-old woman who lived in Britain during the 1980s and 1990s. She died in 2002.

A 23-year-old British man who came to Hong Kong in 2006 was diagnosed that year. According to the latest information, he is now living in Britain.

Early symptoms of vCJD include memory loss, unsteady gait and loss of coordination of limbs, according to the Department of Health. These dementia-like symptoms will worsen and twitching of limbs and trunk also occur. Besides, visual disturbance, abnormal behaviours and seizures can occur. Most patients die within one to two years after onset of symptoms.

The World Health Organisation says there are no reliable tests to use before the onset of clinical symptoms of vCJD. Currently diagnosis can only be confirmed following pathological examination of the brain post mortem.

Says Larsen: “I definitely think there needs to be a rethink on the rules governing blood donation as they are way too strict at the moment.”

A British man who wanted to donate blood at a Red Cross blood-donation drive in his office earlier this year was also surprised when told he could not because of fears over vCJD.

“Cases are very rare judging from my own research, and symptoms generally prove fatal within 12 months. If I had caught this disease before 1996 I’d either be a) long dead or b) a medical miracle. I’m neither,” says the Briton, who spoke on condition of anonymity.

“It sounds crazy and outdated considering both the government and Red Cross are trying to encourage blood donations. I’m not sure how many people in Hong Kong are excluded, but I’m sure it’s a significant part of the city’s population.”

The Red Cross says its donor selection criteria is under regular review by the Hospital Authority and undergoes revision based on the latest scientific and epidemiological evidence.

For more details on blood donation visit 5.ha.org.hk/rcbts