You probably know a thing or two about malaria — the deadliest parasitic disease in the world. But chances are you’ve never heard of visceral leishmaniasis (VL), a neglected tropical disease that is the second-deadliest parasitic disease, and a threat to children and young adults in poverty-stricken regions of the world.

Also known as kala-azar, VL is the most serious of the diseases caused by the leishmania parasite.

VL can become fatal in more than 95% of cases if left untreated. The World Health Organization (WHO) estimates 50,000 to 90,000 new cases occur per year, and between 20,000 and 30,000 people die from it.

Take Action: No Woman Should Suffer From Diseases We Know How to Treat or Prevent

The disease is transmitted by female sandflies infected with the leishmania parasite. Sandflies often breed in poor sanitary conditions, like open sewerage or crowded housing. Deforestation and urbanization have helped them spread into populated areas, which were not previously areas at-risk for infection.

Common symptoms of VL include fever, weight loss, anemia, and an enlarged spleen and liver.

Almost all new cases (90%) were found in seven countries in 2015: Brazil, Ethiopia, India, Kenya, Somalia, South Sudan, and Sudan, where it mostly affects poor and neglected populations as it is associated with populations that have poor housing and malnutrition — people who have weakened immune systems.

An individual's risk of infection is high when others around them become infected — not because the disease is infectious, but because sandflies are likely to be living in the same household.

There is currently no preventative vaccine, but there are highly effective and safe anti-leishmanial medicines available. Access to these medicines has significantly improved thanks to a WHO-negotiated price scheme and a medicine donation program.

In order to prevent further cases of VL, containment efforts that include control measures against sandflies, as well as regional surveillance will be key. Addressing this disease, as well as all NTDs, is essential not only in achieving good health and well-being for all, but also in lifting whole communities out of extreme poverty.

"What You Don’t Know About X" is a new series focusing on neglected tropical diseases (NTDs). NTDs are a cluster of parasitic and bacterial diseases. While you may have heard of a few of them, it’s likely you know very little about their actual effects or why they are so often overlooked. This series looks to shed light on these devastating — and preventable — diseases.