A pandemic is a worldwide outbreak of an infectious disease. The World Health Organization (link opens in a new window) declares a pandemic when the number of cases increases rapidly to cover multiple continents and a significant portion of the population. The difference between a pandemic and an outbreak has nothing to do with virology or the strength of a disease’s transmission; it is purely geographic.
What Are the Risks of a Pandemic?
While the threat of a pandemic differs from event to event, there are certain elements that are common. As the World Health Organization (WHO) says, “Pandemics are global events with a large impact on the global economy and social fabric.”
A cholera pandemic in 1881 spread from India to the Ganges River delta region of Bangladesh, then on to Indonesia and the Philippines. The next year, the disease reached Muslim pilgrims in the Hijaz and Mecca regions of Saudi Arabia and then to Egypt. The disease then spread to Europe via sea and air transport.
In 1918, an influenza epidemic became a pandemic, spreading around the world and killing millions of people, due to close quarters among troops fighting in the trenches during World War I. This pandemic was the deadliest in history.
Since then, there have been four more pandemics, including the current one caused by a new beta-coronavirus. This virus was first identified in 2012, in Saudi Arabia, and later named MERS (Middle East Respiratory Syndrome). The virus is now in Phase 4, which means that it is circulating in the environment and spreading between humans, with community-level outbreaks occurring in at least one country in one of WHO’s six global regions.
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