Communicable diseases include the familiar global scourges, such as HIV/AIDS (human immunodeficiency virus/acquired immune deficiency syndrome), tuberculosis, and malaria, but also include so-called neglected tropical diseases as well as emerging infectious diseases.
HIV/AIDS, tuberculosis, malaria, lower respiratory infections and diarrheal disease cause close to nine million deaths every year, the vast majority of which occur in low- and middle-income countries Lozano et al. 2012). Neglected tropical diseases (NTDs) such as Chagas disease, schistosomiasis, and leishmaniasis are diseases that have traditionally not received the same degree of attention and funding as HIV/AIDS, malaria, and tuberculosis although they impact over one billion people and cause over 500,000 deaths annually (Kealey and Smith 2010). Emerging infectious diseases are infections that are appearing for the first time in a human population or already exist but are increasing in incidence; examples include hantavirus pulmonary syndrome and West Nile fever (Morse 1995, Keesing et al. 2010). Despite concerted efforts and some success in preventing and treating communicable diseases by the global health community, they remain among the leading causes of mortality in many countries, particularly in Africa and south Asia (Lozano et al. 2012). These diseases are spread in several ways: directly from person-to-person through contact with blood or other bodily fluids, from animals to humans, and via airborne pathogens.
Communicable diseases disproportionately impact the poor, both rural and urban, and mortality from these diseases is highest among children under age 5. In recent years, technological advances such as oral rehydration salts for diarrheal disease, triple (pharmaceutical) therapy for AIDS, and vaccines for common diseases like pneumococcal pneumonia have resulted in significant reductions in morbidity and mortality from communicable diseases in some countries. However, low-income countries have had relatively small increases in per capita annual health expenditures from 1995 to 2010 compared with middle-income countries, US $10 to $26 for the former and US $50 to $220 for the latter, and these technologies remain out of reach for many of the world’s poorest people (So and Ruiz-Esparaza 2012).
The economic and societal impacts of common communicable diseases such as AIDS, tuberculosis, and malaria are significant in low-income countries. AIDS often impacts young adults in these countries and can reduce average life expectancy by up to 20 years. Beyond the obvious personal costs, this has major impacts on the work force and can impact overall economic growth. There are significant social impacts as well; it is estimated that about 40 million children worldwide have lost a parent to AIDS. Individuals with tuberculosis, a chronic, debilitating disease, can lose up to four months of work time annually. Treatment for malaria, which most often impacts children in low-income countries, can cost up to 25% of a family’s income (Fonkwo 2008).
Global factors that influence the spread of communicable disease include migration, urbanization, and environmental degradation. More than half of the world population already resides in cities and this trend is expected to continue in coming decades; it is estimated that the urban population in Africa will triple by 2050. The crowded conditions and poor sanitation in many cities, particularly in poorer communities, can serve as the perfect setting for infectious agents to incubate and propagate. Cities also serve as hubs of international travel, which facilitates the spread of pathogens globally (Alirol et al. 2011).
As mentioned, environmental degradation also influences the spread of communicable diseases. Rural residents who can no longer meet their basic needs due to drought, floods, or soil degradation often migrate to cities, resulting in the transmission of predominantly rural diseases to urban populations. For example, the incidence of visceral leishmaniasis is increasing in some Brazilian cities as prolonged droughts in the northeast region of the country have prompted rural migration to cities (Alirol et al. 2011). Furthermore, there is also increasing evidence that biodiversity loss due to environmental degradation may increase transmission of certain infectious diseases such as malaria and schistosomiasis (Keesing et al. 2010).
In 2011, an estimated 34 million people were living with HIV/AIDS globally, with almost two thirds located in sub-Saharan Africa (UNAIDS 2012).Read more
It is estimated that 12 million people are living with tuberculosis worldwide. In 2011, there were almost nine million new cases and more than one million people died from the disease (Glaziou et al. 2013).Read more
In 2010, there were more than 200 million cases of malaria worldwide, causing more than 1.2 million deaths; more than half of these deaths took place in children under the age of 5 (WHO 2013b, Murray et al. 2012).Read more
It is estimated that 1.5 million children die from diarrheal disease every year in low- and middle-income countries, making it one of the leading causes of child mortality in these countries (Kumar and Subita 2012, Ahs et al. 2012).Read more
Acute lower respiratory infections, such as pneumonia, are a leading cause of morbidity, mortality, and hospitalizations among young children globally (Neiderman and Krilov 2013).Read more
Neglected tropical diseases are a group of infections that impact more than one billion people worldwide, and are particularly prevalent among the poorest populations in low-income countries (Kappagoda and Ioannidis 2012).Read more
Emerging infectious diseases such as SARS (severe acute respiratory syndrome) and avian influenza A H5N1 have rapidly spread globally and present significant threats to public health (Coker et al. 2011).Read more