A chemotherapy treatment given to patients with an immune system disorder may work for human avian influenza, but it has not been tested in patients, researchers said on Thursday.

Dr Jan-Inge Henter of the Karolinska Hospital in Stockholm said at the moment it was a theory.

But he and colleagues in Hong Kong believe chemotherapy treatment could work because of the similarities between human infection with H5N1 bird flu and an illness known as haemophagocytic lymphohistiocytosis (HLH).

“Since the mortality from H5N1 infection is high, and since there is concern that the virus could cause a pandemic, novel treatments for human beings are warranted,” Henter said in his hypothesis, published online by The Lancet medical journal.

The H5N1 bird flu virus, which has spread from Asia to birds in Europe, the Middle East and Africa, has killed 94 people since 2003. Global health experts fear the virus could mutate into a pandemic strain capable of killing millions of people.

Henter said human infection with H5N1 produces similar symptoms to people suffering from HLH, an illness that produces too many white blood cells, which can accumulate in healthy tissue and cause organ damage and death.

HLH can be inherited or can develop after a severe infection by a virus such as Epstein-Barr.

Children with the inherited form of HLH usually died until Henter and other scientists developed the chemotherapy treatment in 1994. Henter said the treatment had reduced deaths in children and had produced similar results in people with the secondary form of disorder.

“Now we know that HLH also occurs in patients with avian flu,” Henter explained in an interview. “There are clinical similarities and similarities at autopsy. So why shouldn’t one use a treatment that has been successful in other forms of HLH induced by viruses?” he asked.

The chemotherapy drug etoposide, which helps to kill excess immune cells, is the basis for the treatment for HLH which the scientists believe should be tested on patients with the H5N1 virus.

The treatment is usually given for 8 weeks. Henter said there is risk involved in the treatment but it has improved survival in patients. Side effects can include low blood count and moderate nausea.

“I think it is reasonable to consider this in the medical community. It is reasonable to discuss whether one could initiate a clinical study,” said Henter.

He added that he would welcome the World Health Organization to consider a platform for doing clinical trails of the treatment for human cases of bird flu.