Emerging and Re-emerging Infectious Diseases

Emerging and Re-emerging Infectious Diseases

Emerging and Re-emerging Infectious Diseases

Infectious diseases have had a great impact on human history, killing vast numbers of persons and disabling or disfiguring many others. Some diseases have transformed the social and economic landscape of a region, as when the decline in the peasant population following the Black Death contributed to the end of the feudal system. The fight against smallpox led to the development of vaccination, a weapon in the human arsenal that prevented major loss of life by protecting people from a wide range of diseases (Talan et al 2000). Due to an ever-better understanding of the causative agents of infectious diseases, other tools have been developed to prevent or treat illnesses, including improved sanitation, greater availability of clean drinking water, the increased use of disinfectants, the discovery of antimicrobial compounds, and improvements in the inspection, processing, and preparation of food and drink. The incidence and severity of infectious diseases have fallen in developed nations but are again on the rise worldwide.

Infectious Diseases Today

The leading causes of death due to infectious diseases in the world today are lower respiratory tract infections, diarrheal diseases, HIV/AIDS, tuberculosis, malaria, and dengue hemorrhagic fever and shock syndrome. Many of the victims of these diseases belong to the most vulnerable segments of our population, the very young and the very old, those weakened by other pathological conditions, and those with compromised immune responses. Many other diseases affect smaller segments of humankind (Archibald et al, 2004). Some of these preferentially strike those living in certain climates or ecosystems, in lower socioeconomic groups, or in regions of civil unrest and war. Other diseases are more prevalent in some racial groups, age ranges, occupations, or one gender. Still other diseases are indiscriminate killers. Incidence of some diseases peaks in certain seasons, while others occur year round.

Emerging and Reemerging Infectious Diseases

Many diseases have either been described for the first time within the past 40 to 50 years or have increased in incidence, severity, or geographical range. This text focuses on a number of such diseases and the associated microbes. Several factors in combination have contributed to the explosion of emerging and reemerging infectious diseases in recent times (as evidenced by the Timeline at the end of this chapter). Our awareness of new infections may be due in part to improved detection and understanding of the underlying causes of illness. Many of the emerging diseases, however, appear to be entirely new to humans, while many reemerging diseases represent increasing threats to humankind. Several of the factors believed to contribute to the emergence or reemergence of infectious diseases include microbial evolution, the trend toward increasing urbanization, population migrations between regions or into formerly uninhabited areas, the ease and speed of long-distance movement of persons and materials, natural disasters, climatic and ecological changes, and decreased vaccination rates in many regions of the world. One of the important factors contributing to the rapid emergence of new infections is the increasingly ...