20 times higher. Non-communicable diseases Non-communicable diseases are a series of chronic illnesses such as cardiovascular disease, cancer, injuries, and respiratory diseases, among others. Historically these diseases have plagued developed countries far more than developing countries. In the Global Burden of Disease Study of 2001, it was discovered that 20% of deaths in sub-Saharan Africa were caused by non-communicable diseases. In 2005, the World Health Organization performed a study that showed 80% of chronic disease deaths occurred in low to middle income countries. Non-communicable disease prevalence has been rising in under-developed countries for a variety of reasons. Lack of education and preventive medicine in under-developed countries, along with malnutrition or poor diet lead to many risk factors for non-communicable diseases. Neglected tropical diseases Neglected tropical diseases (NTDs) have been identified by the World Health Organization (WHO) as 18 tropical diseases, affecting over a billion people worldwide, especially in developing countries. These diseases are heterogeneous, meaning originating outside the organism affected by the disease. NTDs are caused by parasites, viruses, and bacteria. NTDs are neglected because they are not normally fatal on their own but are disabling. Persons with these diseases become more susceptible to other NTDs and fatal diseases such as HIV or malaria. Neglected tropical diseases effect can be measured in disability-adjusted life year (DALY). Each DALY corresponds to one lost year of healthy life, whether by death or disability. In the year 2010, it was estimated 26.6 million DALYs were lost. In addition to this, it is estimated NTDs cause a loss of 15–30% of productivity in countries that NTDs are endemic too. According to the CDC, 100% of countries categorized as 'low income' were affected by 5 different NTDs at once. Interdisciplinary approach Tropical medicine requires an interdisciplinary approach, as the infections and diseases tropical medicine faces are both broad and unique. Tropical medicine requires research and assistance from the fields of epidemiology, microbiology, virology, parasitology, and logistics. Physicians of tropical medicine must have effective communication skills, as many of the patients they interact with do not speak English comfortably. They must be proficient in their knowledge of clinical and diagnostic skills, as they are often without high-tech diagnostic tools when in the field. For example, in an attempt to manage the Chagas disease being brought into the almost Chagas-free Brazilian city São Paulo by Bolivian immigrants, an interdisciplinary team was set up. The Bolivian immigrant population