Diseases

What Are Diseases?

Simply put, a disease is an abnormal condition that impairs the normal functioning of an organism. One common differentiation is between communicable or infectious (extrinsic) diseases and non-communicable (intrinsic) diseases. Communicable diseases, ranging from the common cold to HIV/AIDS to malaria and the H1N1 virus, are clinically evident illnesses that result from the presence of some pathogenic agent, such as viruses, bacteria, and parasites. Noncommunicable diseases include cardiovascular disease, cancer, cerebrovascular disease, and hereditary diseases.

According to the Global Burden of Disease: 2004 Update, published by the World Health Organization (WHO), the leading cause of death in 2004 globally was heart disease, followed by cerebrovascular disease (which may lead to, among other things, stroke) and lower respiratory infections. Among the top 12 causes of death, noncommunicable diseases, such as heart disease, cerebrovascular disease, and lung-related cancers, killed almost twice as many people worldwide as did infectious diseases, such as diarrheal diseases, HIV/AIDS, and tuberculosis.

Looking at the leading causes of death by a country's income, a different common categorization can be detected: diseases of poverty, that is, those more prevalent among the poor, versus diseases of affluence, those thought to be a result of increasing wealth in a society. Among low-income countries (by gross national product per capita), the number one killer in 2004 was lower respiratory infections, followed by heart disease, diarrheal diseases, and HIV/AIDS. Remarkably, 6 of the top 10 killers were infectious diseases. However, among high-income countries, noncommunicable diseases topped the list—heart disease, cerebrovascular disease, and lung-related cancers. The only infectious disease among the top 10 was lower respiratory infections.

The spread and control of both communicable and noncommunicable diseases are increasingly relevant to global studies because both are impacted by, and have an impact on, processes and trends related to globalization and internationalization.

The Impact of Global Trends on Disease

Increasing population mobility is considered to be one of the main drivers of the apparently broader and quicker spread of diseases, especially of the infectious sort. According to the World Tourism Organization, the number of international tourist arrivals for business, leisure, and other purposes has risen from less than 100 million in the 1950s to more than 900 million in 2009; by 2020, the number is forecast to increase to nearly 1.6 billion. As people (and the vehicles in which they travel) move around, they may either take with them or introduce pathogens that are endemic to one area or population to other places where the population may not be prepared to handle them. Given [Page 418]that most infectious diseases have an incubation period of more than 24 to 36 hours and that most destinations can be reached—when traveling by air—in less time, the potential for the rapid spread of disease across borders is high.

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