Neglected Tropical Diseases: The Hidden Illnesses Affecting 1.6 Billion People
Understanding the Preventable Diseases That Trap Communities in Poverty
In a small village in northern Nigeria, 12-year-old Ibrahim wakes up each morning with excruciating pain in his legs. His feet and lower legs have swollen to three times their normal size—a condition called lymphatic filariasis, also known as elephantiasis. At school, other children mock his appearance. His family, already struggling with poverty, cannot afford the long journey to the nearest hospital. Ibrahim’s condition worsens each year, and his dream of becoming a teacher seems increasingly impossible. His story represents millions of people worldwide suffering from neglected tropical diseases—a group of 20 devastating illnesses that thrive in poverty, cause immense suffering, yet receive minimal attention from the global health community.
According to the World Health Organization, neglected tropical diseases (NTDs) are a diverse group of 20 conditions that are especially common in tropical areas, where they mostly affect impoverished communities and disproportionately affect women and children. These diseases affect more than 1.6 billion people worldwide—nearly one in five people on Earth. Despite their enormous impact, NTDs receive far less funding, research attention, and public awareness compared to diseases like HIV/AIDS, tuberculosis, or malaria. They trap entire communities in cycles of poverty and suffering that can persist for generations.
What Are Neglected Tropical Diseases?
Neglected tropical diseases represent a diverse collection of infectious diseases caused by various pathogens including bacteria, viruses, parasites, and fungi. What unites them isn’t their biology but rather the populations they affect—the world’s poorest people living in tropical and subtropical regions with limited access to clean water, sanitation, and healthcare.
The WHO’s official list of NTDs includes 20 diseases: Buruli ulcer, Chagas disease, dengue and chikungunya, dracunculiasis (guinea-worm disease), echinococcosis, foodborne trematodiases, human African trypanosomiasis (sleeping sickness), leishmaniasis, leprosy, lymphatic filariasis, mycetoma, chromoblastomycosis and other deep mycoses, onchocerciasis (river blindness), rabies, scabies and other ectoparasitoses, schistosomiasis, soil-transmitted helminthiases, snakebite envenoming, taeniasis/cysticercosis, trachoma, and yaws.
These diseases cause a staggering burden of disability and death. Each year, NTDs kill an estimated 200,000 people and cause millions more to suffer chronic pain, permanent disability, disfigurement, and social stigma. Children are particularly vulnerable—NTDs impair growth and development, reduce school attendance and learning, and limit future economic opportunities.
Like malnutrition and lack of access to essential medicines, NTDs both result from and perpetuate poverty. People living in poverty are more exposed to disease-causing organisms through contaminated water, inadequate housing, and close contact with disease vectors like mosquitoes and flies. Once infected, they often cannot afford treatment or must travel impossible distances to reach healthcare facilities. The resulting illness prevents them from working, further deepening poverty.
Why Are These Diseases “Neglected”?
The term “neglected” reflects several harsh realities about these diseases and the people they affect. NTDs primarily strike the world’s poorest populations—people with minimal political voice or economic power. They occur predominantly in tropical regions of Africa, Asia, and Latin America, far from the wealthy countries where most pharmaceutical companies and research institutions are located.
Several factors contribute to this neglect. First, NTDs affect marginalized populations with limited advocacy capacity. Unlike diseases affecting wealthy populations, there’s minimal commercial incentive for pharmaceutical companies to develop new treatments or vaccines. Research funding is scarce compared to other global health priorities. Many NTDs cause chronic disability rather than dramatic outbreaks, making them less visible in media and less likely to trigger emergency responses.
Additionally, NTDs often carry severe social stigma. Conditions like leprosy, lymphatic filariasis, and leishmaniasis cause visible disfigurement leading to discrimination, social exclusion, and psychological trauma. This stigma discourages people from seeking care and discussing their conditions publicly, further hiding these diseases from view.
The infrastructure needed to control NTDs—clean water, sanitation, vector control, accessible healthcare—requires long-term investment that many endemic countries struggle to prioritize amid competing urgent needs. Like challenges in maternal health and preventing meningitis, addressing NTDs requires strengthening entire health systems, not just deploying specific interventions.
The Devastating Impact of NTDs
Neglected tropical diseases create suffering that extends far beyond physical symptoms. Their impact reverberates through individuals, families, and entire communities in multiple devastating ways.
Physically, NTDs cause chronic pain, severe disability, blindness, organ damage, and death. Lymphatic filariasis causes grotesque swelling of limbs and genitals. Trachoma leads to blindness. Schistosomiasis damages kidneys, bladder, and liver. Chagas disease destroys the heart. Rabies kills virtually everyone who develops symptoms. Snakebite envenoming causes death, amputation, and permanent disability for hundreds of thousands annually.
Economically, NTDs trap people in poverty. Sick individuals cannot work in fields, attend school, or care for families. Treatment costs devastate household finances. Lost productivity reduces community economic output. Studies estimate NTDs cause tens of billions of dollars in economic losses annually in affected countries.
Socially, many NTDs cause disfigurement leading to severe stigma and discrimination. People with visible symptoms face rejection from communities, difficulty finding marriage partners, and exclusion from social activities. Children are bullied at school or forced to drop out. The psychological burden of stigma often equals or exceeds physical suffering.
Developmentally, NTDs particularly harm children. Intestinal worms impair growth and cognitive development. Trachoma causes blindness affecting education and future opportunities. Chagas disease acquired in childhood causes heart problems decades later. The effects compound across generations as sick parents cannot adequately care for or educate their children.
Like mental health conditions broadly, the psychological and social impacts of NTDs often receive insufficient attention despite causing immense suffering.
Common Neglected Tropical Diseases
While the WHO recognizes 20 official NTDs, several cause particularly high disease burdens and illustrate the challenges these illnesses present.
Soil-transmitted helminthiases (intestinal worms including roundworm, whipworm, and hookworm) infect over 1.5 billion people globally—making them the most common NTDs. Children acquire these parasites by ingesting eggs in contaminated soil or food, or through skin penetration by larvae in soil. The worms steal nutrients, cause anemia, impair growth and cognitive development, and reduce school performance. Treatment is simple—a single dose of deworming medication costing pennies—yet hundreds of millions of children don’t receive it.
Lymphatic filariasis (elephantiasis) affects approximately 120 million people worldwide. Mosquitoes transmit microscopic worms that invade the lymphatic system, eventually causing grotesque swelling of legs, arms, and genitals. The disfigurement causes severe stigma and disability. While preventable with annual medication, eliminating transmission requires sustained community-wide treatment for years.
Trachoma, the world’s leading infectious cause of blindness, results from repeated eye infections with Chlamydia trachomatis bacteria. In communities lacking clean water and sanitation, infections pass easily between children. Over years, repeated infections scar the eyelid, causing eyelashes to turn inward and scratch the cornea, eventually causing irreversible blindness. Approximately 137 million people live in trachoma-endemic areas.
Schistosomiasis affects over 200 million people, primarily in sub-Saharan Africa. Parasitic worms released from freshwater snails penetrate human skin during water contact. Inside the body, adult worms live for years in blood vessels, laying eggs that damage bladder, intestines, liver, and other organs. Children playing or swimming in contaminated water face highest infection risk.
Dengue, transmitted by Aedes mosquitoes, causes an estimated 390 million infections annually worldwide—making it the most rapidly spreading vector-borne disease globally. Most infections cause flu-like illness, but severe dengue can cause life-threatening bleeding and organ failure. Climate change is expanding dengue’s geographic range, bringing the disease to previously unaffected regions.
Like leishmaniasis and mycetoma, many NTDs cause disfigurement and disability that devastate lives beyond their physical manifestations.
WHO’s Strategy to Defeat NTDs
In 2021, WHO launched an ambitious roadmap titled “Ending the neglect to attain the Sustainable Development Goals: a road map for neglected tropical diseases 2021–2030.” This strategy aims to reduce by 90% the number of people requiring interventions against NTDs, eliminate at least one NTD in 100 countries, eradicate two diseases (dracunculiasis and yaws), and reduce NTD-related disability and deaths by 75%.
The WHO’s comprehensive approach to defeating NTDs rests on several pillars. First, accelerating programmatic action through preventive chemotherapy (mass drug administration to entire at-risk populations), intensified disease management (diagnosing and treating individual cases), vector ecology and management (controlling insects and other organisms transmitting diseases), veterinary public health (addressing animal reservoirs), and provision of safe water, sanitation, and hygiene (WASH).
Second, mainstreaming cross-cutting approaches including improving data collection and use, fostering research and innovation, ensuring sustainable financing, building partnerships across sectors, and integrating NTD services with broader health systems. Third, supporting country ownership by helping national governments develop and implement their own NTD control programs.
Fourth, adopting strategic enablers such as advocacy and resource mobilization, ensuring access to essential medicines and technologies, promoting equity through targeting the most vulnerable, and positioning NTDs within the broader sustainable development agenda.
This integrated strategy recognizes that defeating NTDs requires more than medical interventions—it demands addressing the social, economic, and environmental factors that enable these diseases to persist. Like efforts to control malaria and eliminate measles, NTD control requires sustained political commitment, adequate funding, and community engagement.
Remarkable Progress and Persistent Challenges
The past two decades have witnessed unprecedented progress against NTDs. Since 2000, more than 42 countries have eliminated at least one NTD. Guinea-worm disease, which affected 3.5 million people in the 1980s, reported only 13 human cases in 2022—bringing eradication within reach. Trachoma elimination has accelerated, with 17 countries validated as eliminating the disease. Sleeping sickness cases dropped by 97% since 2000.
Mass drug administration programs have delivered over 10 billion treatments to more than 1 billion people annually, preventing millions of infections. Pharmaceutical companies have donated billions of doses of medicines—Merck donating ivermectin for river blindness, Pfizer donating azithromycin for trachoma, GlaxoSmithKline donating albendazole for lymphatic filariasis.
However, significant challenges remain. The COVID-19 pandemic disrupted NTD programs worldwide, with mass drug administration campaigns postponed and surveillance reduced. An estimated 1.6 billion people still require NTD interventions. Climate change threatens to expand the geographic range of vector-borne NTDs. Conflict and humanitarian crises disrupt control programs and displace populations into areas with high transmission.
Drug resistance threatens effectiveness of current treatments for some NTDs. Insufficient funding constrains program scale-up and sustainability. Weak health systems in many endemic countries struggle to deliver interventions and integrate NTD services with other health programs.
Prevention and Individual Protection
While comprehensive NTD control requires large-scale public health programs, individuals in endemic areas can take protective measures. Wearing shoes prevents soil-transmitted helminth infections and podoconiosis. Using insecticide-treated bed nets protects against lymphatic filariasis and other mosquito-borne diseases. Avoiding swimming or bathing in freshwater bodies in schistosomiasis-endemic areas prevents infection.
Practicing good facial hygiene and handwashing helps prevent trachoma transmission. Seeking prompt medical care for animal bites and ensuring pets receive rabies vaccination prevents rabies. Avoiding contact with triatomine bugs (kissing bugs) that transmit Chagas disease through improved housing reduces transmission.
However, emphasizing individual responsibility misses the fundamental point about NTDs—they are diseases of poverty and inadequate infrastructure. People shouldn’t need to avoid water because it’s contaminated or live in fear of insects because housing is inadequate. Like micronutrient deficiencies, NTDs ultimately require addressing root causes: poverty, lack of clean water and sanitation, inadequate housing, and insufficient access to healthcare.
The Path to Elimination
Achieving WHO’s 2030 targets for defeating NTDs is ambitious but feasible. Success requires sustained political commitment from endemic countries and international donors, adequate and predictable funding for NTD programs, continued pharmaceutical donations and development of new tools, strengthened health systems capable of delivering integrated services, improved water and sanitation infrastructure, community engagement and ownership of control programs, and addressing social determinants of health including poverty, education, and housing.
Like efforts to improve maternal health and ensure medical device access, defeating NTDs requires comprehensive approaches that extend beyond health sector interventions alone.
Ibrahim’s Future
Two years after we first met Ibrahim, his condition has improved dramatically. His village was included in WHO’s mass drug administration program for lymphatic filariasis. Every eligible person received annual medication preventing disease progression. Ibrahim also learned simple hygiene and leg care techniques to manage his swelling. While his legs haven’t returned to normal size—the damage was already done—they’ve stopped worsening, and Ibrahim no longer suffers constant pain.
More importantly, a local NGO supported by WHO helped establish a support group for people affected by NTDs in Ibrahim’s community. Through this group, Ibrahim found acceptance and friendship with others facing similar challenges. The group advocates for NTD prevention and treatment, reducing stigma and raising awareness. Ibrahim now helps educate younger children about preventing NTDs and pursuing their dreams despite disability.
Ibrahim’s story illustrates both the tragedy and hope surrounding neglected tropical diseases. The tragedy is that his suffering was entirely preventable—if his community had received interventions years earlier, he would never have developed elephantiasis. The hope is that with WHO leadership, political commitment, adequate resources, and community engagement, we can prevent future children from suffering Ibrahim’s fate.
A Call for Justice
Neglected tropical diseases represent one of the starkest health inequities in our world. No child should go blind from trachoma because their community lacks clean water. No one should suffer disfiguring lymphatic filariasis because mosquito control programs don’t reach their village. No person should die from rabies or snakebite because antivenom isn’t available at their local clinic.
The term “neglected” isn’t merely descriptive—it’s an indictment. These diseases are neglected because the people they affect are neglected. Addressing NTDs is fundamentally about justice, equity, and recognizing the inherent dignity and worth of every human being, regardless of geography or economic status.
The tools to prevent and control most NTDs already exist. Effective medicines, proven interventions, and practical strategies are available. What’s needed is political will to prioritize these diseases, adequate funding to sustain programs, pharmaceutical innovation to develop new tools, and global solidarity recognizing that health is a human right, not a privilege determined by birthplace.
By defeating neglected tropical diseases, we don’t just eliminate infections—we break cycles of poverty, restore dignity to marginalized communities, enable children to reach their potential, and demonstrate that humanity values all lives equally. The 1.6 billion people affected by NTDs deserve nothing less than our complete commitment to ending their neglect.
Frequently Asked Questions (FAQs)
Neglected tropical diseases (NTDs) are a diverse group of 20 infectious conditions that are especially common in tropical areas, primarily affecting impoverished communities and disproportionately impacting women and children. They affect more than 1.6 billion people worldwide. They’re called “neglected” because they receive far less funding, research attention, and public awareness compared to diseases like HIV/AIDS or tuberculosis, despite causing immense suffering. NTDs affect politically powerless populations with minimal commercial incentive for pharmaceutical companies to develop treatments. They occur mainly in regions far from wealthy countries where most research happens. Many cause chronic disability rather than dramatic outbreaks, making them less visible and less likely to trigger emergency responses or media attention.
WHO recognizes 20 diseases as NTDs: Buruli ulcer, Chagas disease, dengue and chikungunya, dracunculiasis (guinea-worm disease), echinococcosis, foodborne trematodiases, human African trypanosomiasis (sleeping sickness), leishmaniasis, leprosy, lymphatic filariasis (elephantiasis), mycetoma and chromoblastomycosis, onchocerciasis (river blindness), rabies, scabies, schistosomiasis, soil-transmitted helminthiases (intestinal worms), snakebite envenoming, taeniasis/cysticercosis, trachoma, and yaws. These diseases are caused by various pathogens including bacteria, viruses, parasites, and fungi. What unites them isn’t biology but the populations they affect—the world’s poorest people lacking access to clean water, sanitation, and healthcare.
NTD transmission varies by disease. Some spread through insect vectors (mosquitoes transmit dengue and lymphatic filariasis; flies transmit sleeping sickness and trachoma; sandflies transmit leishmaniasis). Others spread through water contact (schistosomiasis from freshwater snails; dracunculiasis from contaminated drinking water). Soil-transmitted helminthiases spread through contaminated soil. Rabies spreads through animal bites. Chagas disease spreads through triatomine bug bites. People at highest risk include those living in poverty without clean water or sanitation, children (particularly vulnerable to intestinal worms and trachoma), agricultural workers exposed to vectors and contaminated water, and people in rural areas with limited healthcare access. Women often face higher exposure due to water collection duties and face greater social consequences from disfiguring NTDs.
Yes, most NTDs can be prevented and treated effectively. Prevention strategies include mass drug administration (giving preventive medications to entire at-risk populations), vector control (reducing disease-carrying insects through bed nets, insecticides, environmental management), improving water, sanitation, and hygiene (WASH) infrastructure, veterinary public health measures (controlling animal disease reservoirs), and health education. Treatment varies by disease but many NTDs respond to inexpensive medications—deworming drugs for intestinal worms, antibiotics for trachoma and yaws, antiparasitic drugs for schistosomiasis and lymphatic filariasis. Pharmaceutical companies have donated billions of treatment doses. However, access to prevention and treatment remains inadequate in many endemic regions due to weak health systems, poverty, and insufficient program funding.
Significant progress has occurred since 2000. More than 42 countries have eliminated at least one NTD. Guinea-worm disease dropped from 3.5 million cases in the 1980s to only 13 cases in 2022, nearing eradication. Sleeping sickness cases decreased 97% since 2000. Seventeen countries have eliminated trachoma. Over 10 billion treatments have been delivered to more than 1 billion people through mass drug administration programs. WHO’s 2021-2030 roadmap aims to reduce by 90% the number of people requiring NTD interventions, eliminate at least one NTD in 100 countries, eradicate guinea-worm disease and yaws, and reduce NTD-related deaths and disability by 75%. However, challenges remain including COVID-19 disruptions, climate change expanding vector ranges, insufficient funding, and weak health systems in endemic countries.
References
- World Health Organization. (2024). Neglected tropical diseases. Retrieved from https://www.who.int/health-topics/neglected-tropical-diseases
- World Health Organization. (2024). Neglected tropical diseases – Fact Sheet. Retrieved from https://www.who.int/news-room/fact-sheets/detail/neglected-tropical-diseases
- World Health Organization. (2024). Ending the neglect to attain the SDGs: A road map for NTDs 2021-2030. Retrieved from https://www.who.int/initiatives/defeating-neglected-tropical-diseases-2021-2030
- World Health Organization. (2024). Neglected tropical diseases: Progress dashboard. Retrieved from https://www.who.int/teams/control-of-neglected-tropical-diseases/overview
- World Health Organization. (2024). NTD data and country profiles. Retrieved from https://www.who.int/data/gho/data/themes/neglected-tropical-diseases
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