With medical advances and international co-operation, some countries have made great strides in treating and even eliminating certain disease.
The number of malaria deaths fell by 60% globally between 2000 and 2015, according to the World Health Organisation (WHO), and Nigeria has been polio-free for more than a year now. But what works in one country may not do in another, as illustrated by the tropical disease, visceral leishmaniasis, also known as kala azar.
The disease is caused by a parasite, which is spread by the bite of infected sandflies, and results in fever, weight loss, anaemia and the enlargement of the liver and spleen. If left untreated, it is almost always fatal. According to the WHO, each year there are an estimated 300 000 new cases, and more than 20 000 deaths, from the kala azar. About 90% of these occur in Bangladesh, Brazil, Ethiopia, India, Nepal and Sudan.
Last year the WHO announced that three south Asian countries – Bangladesh, India and Nepal – were on the verge of eliminating kala azar as a public health problem, following a 75% drop in new cases between 2005 and 2014.
This was achieved, it said, through a strategy that involved, among other things, early diagnosis using rapid diagnostic (finger prick) tests, disease surveillance, vector management (pest control) and the use of a new medication, AmBisome, for treatment.
Although the drug can be expensive, the WHO has secured a preferential price of $18 per vial from the drug's producers, Gilead. In 2011, Gilead also donated 445 000 vials of the drug for the treatment of patients in endemic countries, through the WHO.
Kala azar: The killer disease nobody knows about
supports HTML5 video
Kala azar is endemic in parts of South Sudan and affects mostly the poor and disenfranchised. A simple jab could control it, but not in this country.
Game changerAmBisome was a game changer for kala azar – it enabled doctors to treat the disease with a once-off, intravenous infusion. This doesn't necessarily cure someone for life, according to Koert Ritmeijer, the research coordinator for neglected tropical diseases in the public health department at Médecins Sans Frontières (MSF). This, he says, is because leishmania parasites can remain hidden in the internal organs and the disease can flare up when the patient's immune system is weakened because of illnesses such as HIV infection or tuberculosis. But it does provide significant relief.
"In South Asia a single dose of AmBisome will cure the patient, just as any other effective treatment. However, no drug or treatment will achieve sterile cure [a lifelong cure]," he says.
But according to a 2010 study published in the Journal of Global Infectious Diseases, AmBisome doesn't work as well in East Africa. The sub-species of parasite present in East Africa reacts differently to the drug.
"Whereas in South Asia one single dose of AmBisome is 97% effective and does not require hospitalisation, in East Africa six doses are only about 90% effective, and require 12 days of hospitalisation," he says.
Ritmeijer says the drug also needs to be transported and stored at a specific temperature and it must be administered by higher level health staff, such as doctors, clinical officers or professional nurses, at a hospital.
Good drugs neededSome East African countries, such as South Sudan, have seen decades of civil war, armed conflict and insecurity. Infrastructure is poor and there is a shortage of healthcare facilities, medical personnel and drugs.
According to the International Committee of the Red Cross, there were only 120 doctors for a population of nine million in 2012. A 2015 WHO country briefing document explains that a third of all healthcare facilities in the country – including the main referral hospitals in Bor, Bentiu and Malakal – have been looted and destroyed.
So instead, the standard treatment in South Sudan consists of two drugs, administered through painful intramuscular injections, every day for 17 days. These drugs, developed in the 1940s and 1950s, can have serious side effects, including acute inflammation of the pancreas, kidney damage and even cardiac arrhythmia. However, patients who receive this treatment generally require minimal monitoring, so it's possible to treat them as outpatients. The drug also has much better heat stability, according to Ritmeijer, and is not as easily affected by the high temperatures common in South Sudan as AmBisome is.
"There are no good alternatives," says Ritmeijer. "We're still depending on drug development, which is very slow, specifically because the pharmaceutical industry is not interested in developing drugs for kala azar; it's not a profitable market."
South Sudan suffersThe South Asian countries' efforts to eliminate kala azar have been successful so far, Ritmeijer says, because they have the right tools – simple diagnostics and a single, short treatment, target populations that live in densely populated areas with good infrastructure and access to hospitals, as well as significant aid money to improve access to diagnostics, treatment and vector control.
But the WHO says South Sudan has no national control programme, no vector control or bed net distribution programme, and disease monitoring is not mandatory.
"The tools that we have in terms of diagnostics, drugs and vector control tools are inadequate [for eliminating kala azar], but at least we can try to improve access to treatment for patients," Ritmeijer says. "It's not necessary that we have to treat people with drugs that were developed a hundred years ago."
* This story was updated on 17 March 2016 to include more information on the price of AmBisome and the drugs used in South Sudan to treat kala azar. The story originally referred to AmBisome as being administered via injection. The drug is administered via intravenous infusion. This was corrected on 21 March 2016.
Have something to say? Tweet or Facebook us on @Bhekisisa_MG
It's war on tropical diseases
NGOs speak: Their most pressing humanitarian priorities for 2016
Anti-TB compounds could fight neglected diseases
Health workers brace for an increased need for palliative care as waiting lists grow.
Have something to say? We can help you say it – but only if you promise to read this first.
In this township, alcohol makes violent men close to three times more likely to rape a woman.
Bhekisisa means "to scrutinise" in Zulu
In South Africa, Zulu patients who would like to be thoroughly assessed by a doctor, would ask the physician to "bhekisisa" them.