The emergence of the new H1N1 influenza virus last year grabbed the attention of health authorities and many of the world’s people. This never-before-seen disease spread quickly across the globe, causing illness and death and triggering a major public health response. But while the virus itself is new and unique, some researchers say it is just the latest in a long line of infectious diseases that share common ancestry in the way that they spread.
Infectious diseases are responsible for more than a quarter of deaths annually in the world. Dating back to the earliest days, viruses have had a huge toll on human health. Yellow fever, for instance, claimed 3.5 million lives, and the plague, ominously referred to as the Black Death, killed 50 million people across Europe and Asia in the 14th century,.
Disease experts and medical historians have traced outbreaks of disease through history. In a study last year, (PDF) researchers found similarities in what caused their spread.
The most significant cause found was the movement of humans. For example, disease spread along trade routes. As more and more trade routes popped up, more and more groups of people became connected, enabling disease to spread farther faster. (Just think about the impact of modern air travel.) Poverty and social inequality, and war and famine have similarly affected patterns of movement and the sharing of viruses.
Another common contributor to disease spread was the emergence of new technology and industries. The re-emergence of dengue fever, for instance, was sped in part by the preference of the disease-carrying mosquito to lay its eggs in discarded tires and metal cans.
As our world becomes more complex, opportunities for diseases to emerge are greater. New threats like H1N1 will continue to arise, and infectious disease, as it has throughout recorded history, will remain a challenge to human survival. Lessons learned from both ancient and modern plagues can help us better understand how diseases spread and reduce their impact in the future.