Emerging infections: a perpetual challenge

Abstract

Emerging and re-emerging infectious diseases, and their determinants, have recently attracted substantial scientific and popular attention. HIV/AIDS, severe acute respiratory syndrome, H5N1 avian influenza, and many other emerging diseases have either proved fatal or caused international alarm. Common and interactive co-determinants of disease emergence, including population growth, travel, and environmental disruption, have been increasingly documented and studied. Are emerging infections a new phenomenon related to modern life, or do more basic determinants, transcending time, place, and human progress, govern disease generation? By examining a number of historically notable epidemics, we suggest that emerging diseases, similar in their novelty, impact, and elicitation of control responses, have occurred throughout recorded history. Fundamental determinants, typically acting in concert, seem to underlie their emergence, and infections such as these are likely to continue to remain challenges to human survival.

Figure 1

Newly emerging, re-emerging/resurging, and deliberately emerging diseases (A) Selected emerging diseases of public-health importance in the past 30 years (1977–2007),, with representative examples of where epidemics occurred. (B) Selected emerging diseases of public-health importance in previous centuries (430 BC to 1981). MDR=multidrug-resistant. SARS=severe acute respiratory syndrome. vCJD=variant Creutzfeldt-Jakob disease. XDR=extensively drug-resistant.

Figure 2

Examples of modern and historically important emerging infectious diseases (A) Emerging epidemics caused by war and famine. Plague in an Ancient City, by Michael Sweerts, circa 1652, represents the Plague of Athens. Oil on canvas, Los Angeles County Museum of Art, CA, USA. The infamous epidemic, the cause of which is still unidentified, occurred during the Peloponnesian wars between Athens and Sparta (430–426 BC). (B) Emerging epidemics associated with intent to harm. The Black Death (bubonic/pneumonic plague) of 14th century Europe was associated with a bioterrorist attack at Caffa., , The untitled and anonymous painting has been referred to as Death Strangling a Victim of the Plague (circa 1376; Clementinum Collection of Tracts by Thomas of Stitny, also known as Stitny Codex, University Library, Prague, Czech Republic). Photo credit Werner Forman, Art Resource/NY. (C) Emerging epidemics due to travel and trade. Honoré Daumier's depiction (hand-tinted woodcut) of the 1832 Paris choléra-morbus epidemic, which spread slowly from Asia to Europe along established travel routes. National Library of Medicine, History of Medicine Division. (D) Emerging epidemics associated with microbial adaptation and change. A Maori (New Zealand Polynesian) cenotaph (monument honouring the dead) at a marae (meeting place), Te Koura, New Zealand, memorialises those who died in the 1918–19 influenza pandemic. Photographed by Albert Percy Godber. Cenotaph designed and carved by Tene Waiter. Alexander Turnbull Library, National Library of New Zealand, Wellington, New Zealand.

Figure 3

Average travel time between England and Australia, 1925–2000 As travel times between distant places have decreased markedly in the past nine decades, the potential for human importation of diseases, especially those with long incubation periods—even if they are easily identifiable—is greatly increased, thereby increasing the potential for re-emergence of epidemic diseases via spread into new geographic areas. The serial generation time of measles is approximately 14 days. Adapted from Cliff et al, 2000, by permission of Oxford University Press.