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ost of us cannot imagine that there are hidden diseases that affect billions of the world’s population that have been neglected for so many years. Nevertheless, as hard as this may be to believe, this is indeed the case with neglected tropical diseases (NTDs).

NTD is a group of diseases most commonly found among the 2.7 billion people in the world who live on US$2 per day. More than 1 billion people in 194 countries across Asia, Africa and South America are affected by one or more of the diseases in this group. These diseases thrive in conditions of poverty, malnutrition, bad sanitation and unsafe or limited water supply. They are “hidden” in the most rural and remote areas among the poorest of the population.

The term neglected can’t be more precise since it represents the failure to give attention to the people who have these diseases, as well as the failure to do something about these diseases.

The group of NTDs includes but is not limited to buruli ulcer; human African trypanosomiasis (sleeping sickness); dengue/dengue haemorrhagic fever; leishmaniasis; Chagas disease (American trypanosomiasis); leprosy; lymphatic filariasis (elephantiasis); rabies; soil transmitted helminthiasis; trachoma; dracunculiasis (guinea worm disease); schistosomiasis and onchocerciasis (river blindness). AIDS, tuberculosis and malaria are not included in this group, as they are no longer neglected and have already received the necessary attention, funding and eradication efforts.

NTDs are easily overlooked as they seem to not cause high number of death. However, they still impact the poorest of the poor in different ways. They can infect an individual without being noticed, spread over the period of years, sometimes decades, and only later cause deformities, disabilities and blindness. Child growth, development and physical fitness are impaired, and their potential future earnings reduced. This in turn, will further lead to what is called the poverty trap of disease, as mentioned by Paul Collier in his book The Bottom Billion, where diseases put people into poverty, or prevent them and their offspring from getting themselves out of poverty.

As acknowledged by the World Health Organization (WHO), the neglect of these diseases is present at the community, national and international level. The diseases most often affect the poorest and most marginalized people, who have no political voice. Efforts to overcome these diseases have not yet become an important priority for the governments. At the international level, the diseases are not seen as a threat to the western or developed countries as they require specific environmental factors in the tropics that mean they do not travel easily to other part of the worlds. Because of the small market potential, pharmaceutical companies have little interest in supporting research and manufacturing diagnostic tools or new drugs. This in turn hinders researchers from developing new and effective treatments.

NTDs cause disability and stigma, and prevent individuals from being able to earn a living, take care of their family, or even participate in a day-to-day social life. Lymphatic filariasis is an example. It is a disease caused by worms that block the lymphatic vessels in the body and can cause severe swelling in the leg (from which it gets its name elephantiasis) or the genital area. A study in Sri Lanka showed the painful reality caused by the disease. The researchers interviewed people with filariasis from low-income households. They revealed that even when drugs for filariasis were provided for free, the high transportation cost to health centers still prevented people from seeking treatment. As the disease progresses, surgery might be needed, which for most of the people affected was simply not affordable.

Failure to treat filariasis in the early stages exacerbates the enlargement of the limbs, which can cause the sufferer to be isolated by their community. Sources of income are lost as many lose their jobs due to the stigma and physical disability caused by the disease. On a larger scale, contracted by agricultural workers can cause a reduction in agricultural productivity and harvest.

The neglected face of the disease can also be seen in how poor the treatment choices are. Most available drugs are either very old, costly, toxic, or even deadly. In the case of rhodesiense human African trypanosomiasis, the later stages of the disease can only be treated with one old drug – melarsoprol – which uses the toxic heavy metal arsenic as an ingredient. The drug started being used in 1949. In late stages of trypanosomiasis, 10 percent of patients treated with melarsoprol develop a brain dysfunction called encephalopathy as a side effect of the drug, and 5 percent of these patients die due to the toxicity of the drug.

Within the field of research and development of new drugs, the danger of emerging drug resistance is always present. This challenges researchers to find new strategies to tackle NTDs. Many diagnostic tools or drugs are currently being investigated in laboratories, but they are yet to be tried on real patients, a process that may take years before they can finally be approved for use.

WHO has prioritized key tools in efforts to tackle NTDs such as providing free treatment, ensuring the distribution of these free drugs, environmental management to prevent the spreading of the diseases, as well as development of new diagnostic tools and drugs.

It is estimated that more than $3 billion will be needed over the next five years to sustainably fight NTDs, not to mention extended funding for new drugs, diagnostic tools and vaccines. Large pharmaceutical companies have donated several drugs for NTDs although most only meet 5 percent to 63 percent of the world’s need. Even with adequate funding, some fragile countries face extra challenges in combating NTDs such as poor governance, authoritarian regimes, conflict, marginalization of certain groups and violation of human rights.

For so long, these hidden diseases along with the neglected people have been out of sight and marginalized. It is time to realize that now the commitment and perseverance to combat NTDs is crucial, not just to eliminate health problems, but also to reduce poverty and meet the basic human rights to health and equality.