A blood donor has been found in Australia as part of a global search to help an American toddler who has an extremely rare blood type.

Three-year-old Zainab Mughal requires frequent blood transfusions for cancer treatment.

Key points: A fifth donor with an extremely rare blood type has been found in Australia

A fifth donor with an extremely rare blood type has been found in Australia Their blood has been sent to Florida for use in the stem cell transplant operation

Their blood has been sent to Florida for use in the stem cell transplant operation Only about 4 per cent of people of Indian, Pakistani and Iranian background have the rare blood

There are over 300 different blood types, and 90 per cent of the population is fairly easy to match to one of those types.

The challenge for the doctors treating Zainab is that her blood type only occurs within Indian, Pakistani or Iranian communities and so far, only five donors around the world have been tracked down.

Adjunct Professor David Irving is the director of research and development with the Australian Red Cross Blood Service, which found the match for Zainab.

"Zainab has one of these [blood types] where she is actually missing a particular blood group antigen called Indian," he said.

"That particular characteristic of blood is only found in people from India, Pakistan and Iran — in fact, only about 4 per cent of those people have that particularly rare blood group."

Sorry, this video has expired Zainab Mughal's parents talk about the search for a blood donor.

The Australian Red Cross Blood Service has been helping out in the global search.

"We have a rare blood donor panel ourselves, [with] about 400 or 500 people registered on that particular panel," Professor Irving said.

"So we search through that panel, identify people of particular blood types — and we found one.

"In fact, we've got four people on that particular panel here in Australia who are Indian negative blood type."

Two of the identified possible donors in Australia have not yet been located, but one who was able to be contacted donated blood at the donor centre in Sydney the day before Australia Day.

"It is a day where we celebrate cultural diversity and multi-ethnic background, and it was really quite exciting that we were able to find that donor," Professor Irving said.

Blood shipped around the world

The blood collected from the Australian donor has been sent to Florida, for use in Zainab's stem cell transplant operation.

This process has been aided by an effective system that has been established for the international tracking of blood.

"When it has been processed, we go through a number of different steps to make sure that it is safe and it is going to be stored in appropriate conditions," Professor Irving said.

"It can be stored for up to six weeks at four degrees, fridge temperature.

"We ourselves get occasional blood samples coming in from other countries, as well to help with some of the patients that aren't able to be matched by our local donors as well."

Zainab with the medical team overseeing her treatment. ( OneBlood )

The search continues

Zainab still needs more blood for further treatments, so the search for donors will not stop at five.

OneBlood is a not-for-profit blood centre serving the Florida area that has been working hard to find donor matches for Zainab as she prepares for a bone marrow transplant operation.

The group hopes to expand the pool of donors to at least seven to 10, in order to support the toddler's long-term blood transfusion needs.

Professor Irving said Australia's population diversity means more donors could likely be found here.

"We are certainly looking to diversify our blood donor pool so that we are ready for those patients like Zainab who come along from time to time," he said.

"Our red cell reference laboratory researchers are working hard to make sure that they do get the best match for all of the patients who are in need of red blood cell transfusion."

He encouraged anyone who thought they could be a match for a rare blood type to contact the Australian Red Cross Blood Service.

"Our call centre on 13 14 95 would be more than happy to take calls from people who have got different ethnic origins from others," he said.

To be a match for Zainab a donor must be exclusively of Pakistani, Indian or Iranian descent — meaning the donor's birth parents are both 100 per cent Pakistani, Indian or Iranian — and must also be blood type O or A.