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PLOS BLOGS Speaking of Medicine

Neglected Tropical Diseases that Kill

According to the latest (November 28) figures from the World Health Organization (WHO) and US Centers for Disease Control and Prevention, almost 6,000 people have died so far in the 2014 Ebola outbreak in West Africa, with estimates that the deaths will easily exceed 7,000 deaths before year’s end.

There is no question that Ebola virus infection is one of the most lethal of all of the neglected tropical disease (NTD) pathogens, but on a global scale there are a number of other NTDs that also cause large numbers of deaths.

The WHO currently lists 17 major disease conditions as NTDs.  Shown in Fig. 1 is an illustration from our previous publication in PLOS Neglected Tropical Diseases that compares the proportion of disability-adjusted life years (DALYs) that result either from disability (YLDs – years lived with a disability) colored in blue, or death (YLLs – years of life lost) colored in orange.   It’s clear that there is a lot more blue than orange meaning that most of the world’s NTDs are disablers rather than killers.  But there are also important exceptions such as the kinetoplastid infections, including leishmaniasis (kala-azar), African sleeping sickness, and Chagas disease, as well as the viral infections rabies and dengue fever which also represent major killers.  Schistosomiasis, which is a major disabler, is another important cause of mortality in Africa.

Hotez et al.
Hotez et al.

Indeed, if we compare the number of people who have died in this year’s Ebola epidemic with the number of deaths caused by NTDs from the Global Burden of Disease Study 2010, we find that there are some very serious and lethal NTDs that get very little attention.  At least six NTDs kill more people each year than all those who perished from Ebola virus infection this year.

Our takeaway is that while we urgently need new drugs, diagnostics, and vaccines for Ebola virus infection, the same could be said for all of the NTDs listed in Table 1.  As the global policy leaders in the United States, Europe, and elsewhere meet in the coming weeks and months, we hope they will consider new Ebola virus technologies in the context of each of our planet’s killer NTDs.

Table 1. Deaths from the NTDs and Ebola virus infection (modified from Refs. 1 and 3)

Neglected Tropical Disease Deaths Year
Leishmaniasis 51,600 2010
Rabies 26,400 2010
Dengue fever 14,700 2010
Schistosomiasis 11,700 2010
Chagas disease 10,300 2010
African trypanosomiasis   9,100 2010
Ebola virus infection 6,000-7,000 2014
Intestinal nematode infections   2,700 2014
Cysticercosis   1,200 2014
Echinococcosis   1,200 2014
Discussion
  1. […] This morning, Dr. Peter J. Hotez, M.D., Ph.D., the Dean of the National School of Tropical Medicine, gave a talk at UTSW titled “Neglected Tropical Diseases, Anti-Poverty Vaccines, and Blue Marble Health.” With the inundation of Ebola news, many of the more common (and more deadly) tropical diseases are forgotten. Take a look at this data, posted by Dr. Hotez, about Neglected Tropical Diseases that Kill. […]

  2. Two questions: 1. Why is yellow fever (30,000 deaths annually per WHO) not considered a neglected tropical disease (?availability of effective vaccine – are the programs in place to increase vaccination adequately funded?)? 2. Why no YLL for yellow fever in the chart?

  3. Thanks for your email. At PLOS NTDs we certainly do consider YF as an NTD. You would need to inquire with WHO about their list, however, I just noticed that they now call it “dengue and chikungunya”
    http://www.who.int/neglected_diseases/diseases/en/
    so perhaps they might consider enlarging to an “arbovirus” category. Regarding the DALYs and deaths, I believe the GBD 2013 is doing a deeper dive on YF so we might see revised estimates. I hope that helps a little!

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