Learning from Past Pandemics

Gisele Norris


November 1, 2009

Pandemics are rare events. Our understanding of them comes mainly from data and information obtained from studying four events over the past 120 years: the 1889 "Russian Flu" pandemic, the 1918 "Spanish Flu," the 1957 "Asian Flu" and the 1968 "Hong Kong Flu."

One of the fundamental lessons learned from the past is that pandemics occur in waves. A pandemic wave is a fluctuation in the number of pneumonia- and influenza-related infections and deaths over a given period in a specific geographic location. The term "wave" relates to the number of infections building up, peaking and subsequently tapering off, and the duration and intensity of each wave can vary greatly from pandemic to pandemic-and even within individual pandemics. The reasons for multiple waves of varying impact are not precisely understood, but they probably include adaptation of the virus to its new host, demographic or geographic variation, seasonality and the overall immunity of the population.

Three identifiable waves characterized the Russian Flu pandemic. The waves were spread out over a period of three years with demarcated inter-pandemic periods between each wave. The first wave occurred between the spring and winter of 1889 and moved slowly but steadily throughout the world, causing high morbidity but low mortality. The second wave occurred a full year later in the spring of 1891 and caused high mortality. The third wave occurred in early 1892 and was relatively mild.

The "Spanish Flu" was even more devastating, infecting approximately 500 million people and killing at least 50 million-and possibly as many as 100 million. In the United States, the 1918 pandemic killed as many as 675,000 people, with the highest incidence of death occurring among adults under 45 years of age. The mortality rate in Europe and the United States during the 1918 pandemic was 2.5%. By comparison, mortality rates during the 1957 and 1968 pandemics were 0.02% and 0.01%, respectively.

In the case of the 1918 pandemic, three waves occurred in quick succession over a 12-month period with each wave barely separated by an inter-pandemic period. The first wave occurred in the spring and summer of 1918 with isolated outbreaks occurring unevenly throughout the United States and Europe. During this wave, morbidity rates were high but mortality rates were unremarkable. The second wave occurred in the fall of 1918, more specifically between September and December. This wave produced a flood of illness and death in a very short span of time that was simply overwhelming. The third wave occurred in early 1919 and had lower morbidity and mortality rates.

In the case of the 1957 pandemic, the waves were drawn out over a five-year period. During the 1968-1970 pandemic, the first influenza season led to a high mortality rate in the United States and had little impact on the rest of the world. During the second influenza season, many parts of the world were affected, but the pandemic actually unfolded as a series of smoldering localized epidemics, rather than acute spikes in mortality as was characteristic during the 1918 and 1957 pandemics.

As a pandemic unfolds, businesses should be attuned to patterns of disease diffusion in order to prepare their employees and businesses accordingly. For example, businesses should be prepared to react appropriately as illness and subsequent absenteeism builds, reaches a peak and ebbs. Businesses should also have a plan for action between one wave and the next.

Questions that should be addressed may include:

  • How is demand for your product or service likely to be affected during and between each wave?

  • What are your requirements and commitments with suppliers and customers? How might these be affected when the pandemic is at its peak?

  • What circumstances could precipitate a shutdown of your workplace?

  • What trigger will you use to  re-open the workplace?

  • Are alternative work arrangements available for employees who are not ill but still unable to come in?

  • How will you communicate with your employees at different points in the pandemic wave? What messages will you broadcast?

The dynamic nature of pandemic flu compels employers to track and understand the pattern of spreading disease. By considering various scenarios and planning for the resulting contingencies, business leaders prepare their businesses to react to the ebb and flow of the disease and the effects that this pattern will have on its employees, suppliers and customers.
Gisele Norris, DrPH, is managing director for Aon Healthcare's western region, where she develops innovative risk solutions for health care organizations. Most recently, she was a primary leader of Aon's Pandemic Preparedness Task Force.