Each year, 50,000 people die of kala azar, a tropical disease which is transmitted by sandflies. There are few effective drugs to treat it; those that are available are mostly not affordable for people in poorer countries. Without treatment, nine out of ten patients will die.

When Sunder Devi, 25, reached the hospital in Hajipur in the Indian state of Bihar, she was more dead than alive. She was suffering from kala azar, as are so many in Bihar: this is the region most affected by this disease in the whole world.

"When patients like Sunder Devi come to us they have mostly been suffering for weeks from fever, tiredness, loss of appetite, and weight loss. Just by palpating their bellies, you can tell that the spleen is greatly enlarged," explained Gaurab Mitra, an Indian doctor who works with MSF in the hospital's kala azar ward.

What begins with flu-like symptoms develops over a period of months into a life-threatening illness. The infectious agent - a parasite which is transmitted by sandflies - damages the immune system, making the sufferers susceptible to other diseases such as pneumonia or tuberculosis. Not only that, but they also suffer from acute anaemia. It takes weeks after the onset of the disease for the typical symptoms fully to emerge: a swollen abdomen, anaemic skin pallor and wasted extremities. Even though the disease is life-threatening and affects tens of thousands of people, it hardly attracts any public attention.

The World Health Organisation (WHO) classes kala azar - along with 13 other diseases - as a "neglected tropical disease". Only a very few institutes or pharmaceutical companies are investing time and money in research into it, with the consequence that very few new drug treatments are being developed; and there is no vaccine.

Neglected tropical diseases like kala azar primarily affect people in poorer countries, which represent an unattractive market because most of their inhabitants cannot afford to pay for the drugs. This is reflected in the hospital in Hajipur. Many of the kala azar sufferers belong to the lowest Indian caste: the Musahar.

"These people are the poorest of the poor. They work as casual labourers in the fields or tend cattle. They sleep in huts of mud and straw and are thus especially vulnerable to the bites of the sandflies," said Gaurab Mitra. "While it is true that the sufferers do find help in the national health centres, they are frequently only treated using outdated drugs."

Such a drug is Pentostam, which was developed in the 1930s. Treatment with Pentostam requires a painful course of injections directly into the muscles over a period of up to 40 days, with numerous side effects. This treatment is, in any case, often fruitless: in some parts of India where the disease is endemic, over 60 percent of the pathogens have developed resistance to the antiquated drug. MSF in Bihar is therefore using a newer drug, liposomal amphoterycin B, marketed under the brand name Ambisome.

"This is a very good drug. We have treated around 1,700 patients with it since July 2007 - sufferers can recover in as little as ten days," said Gaurab Mitra. "In Sunder Devi's case, it took somewhat longer because she was also infected with hepatitis. But we were still able to discharge her after four weeks."

However, even the Ambisome drug has a disadvantage: its cost. Even after a sharp fall in price, it still costs about US$280 to treat each patient. This is a price many people in poorer countries are unable to pay, making it more difficult to establish the widespread use of the drug in Indian health centres.

MSF's Access Campaign is challenging the pharmaceutical industry to make further reductions in the price of Ambisome and allow the production of cheaper combination drugs. MSF is also calling on governments to make more money available for research into neglected diseases and to push for the development of improved testing procedures, drugs and preventative vaccines: this in the hope that the future will see more patients like Sunder Devi returning home restored to health after successful treatment.