History teaches us that epidemics can occur at any time, in any place on Earth, with no regard to the systems of government in place, or to the development levels of the areas they affect. Diseases such as the bubonic plague – which ravaged Europe during the mid-14th century – affected people from all socio-economic environments, of all ages, and regardless of gender. The same can happen in present times, with the only difference being the fact that now it can happen a lot quicker.
 

While population mobility was praised for connecting people everywhere and for making the world smaller, it is also the main reason why the severe acute respiratory syndrome (SARS) jumped from Hong Kong to Toronto in a matter of days. Infected passengers, traveling by airplanes, buses or trains, can nowadays infect very high numbers of other people, unlike 500 years ago, when the first signs of an epidemic prompted a thorough curfew.
 

In the current economic environment, it's impossible to shut down an entire city, if signs of disease appear. No matter how serious the infections, hospitals will try to deal with it, while the rest of the town goes about its usual business. While this may help maintain the economy, it does not solve the issue of widespread contamination, which can occur even if one person carrying an infectious virus escapes the quarantine zone.
 

"The art of predicting disease emergence is not well developed. We know, however, that the mixture of determinants is becoming ever more complex, and out of this increased complexity comes increased opportunity for diseases to reach epidemic proportions quickly," explained David Morens, M.D., a scientist working with the National Institute of Allergy and Infectious Diseases, one of the authors of a recent article on the spread infectious disease, published in The Lancet Infectious Diseases.
 

In order to prevent widespread pandemics, scientists have to take into account a large number of factors, both natural and man-made, that could cause a harmless virus or bacteria to mutate into a devastating infectious agent. Large population movement routes, such as airport terminals and important, trans-continental highways, should be scanned regularly, so as to prevent the spread of diseases through these corridors.