Pandemic Overview

Updated: November 2022

What is a pandemic?

A pandemic is a world-wide disease outbreak. Several human flu pandemics occur each century, affecting millions of people. The last influenza pandemic was in 2009-2010 and experts agree it is inevitable another will occur.

COVID-19 is caused by the severe acute respiratory syndrome coronavirus (SARS-CoV-2) and was declared a pandemic in March 2020.

How do pandemics occur?

Pandemics can occur when a "new" virus emerges that has the following properties:
  1. Humans have little or no immunity to it,
  2. The virus can cause significant illness or death,
  3. The virus can be spread easily from person to person.
If these three criteria are met, the virus can then spread globally. The severity of the pandemic depends on the qualities of the virus. Some cause more severe illness and are more infectious than others.

Previous pandemics

1918 Pandemic (H1N1 virus): Considered the most severe pandemic in the 20th century, the 1918 influenza ("Spanish Flu") pandemic occurred immediately after World War 1 and lasted about 15 months. Even though this was the era before commercial airline travel, the disease spread across the world within 2 months. It was a global catastrophe. Approximately 30 percent of the world's population was infected and about 50 million people died - many within 48 hours of becoming ill. It was caused by an H1N1 strain of influenza A. The virus may have originated in Northern France or the USA. One of the current seasonal influenza strains is a “descendant” of this virus.

Several “waves” of infection occurred. The first wave of illness struck Europe, Asia, Africa and the USA. WHO described this first wave as “not especially deadly.” The second wave caused greater numbers of infection and saw more deaths.

Highs mortality was seen in people younger than 5 years old, 20 to 40 years old, and 65 years and older. A unique aspect of this pandemic was the high mortality in health people, particularly those in the 20 to 40 year age group. No antibiotics or vaccinations were available during this pandemic. Quarantine efforts did not prevent the disease from spreading globally, except possibly to delay its introduction into Australia.

1957 Pandemic (H2N2 virus): The virus responsible was first identified in East Asia. It was caused by an A/H2N2 strain of influenza A, which no longer circulates in humans. Low immunity rates in people less than 65 years of age allowed scientists to predict a pandemic and a vaccine became available in August 1957. The pandemic occurred in waves and most deaths occurred between September 1957 and March 1958. Death rates were highest in the elderly.

1968 Pandemic (H3N2 virus): In early 1968, an influenza pandemic virus was first detected in Hong Kong and was caused by an A/H3N2 strain of influenza A. The pandemic lasted from September 1968 until March 1969. Deaths from this virus peaked in December 1968 and January 1969, with those over the age of 65 most likely to die. A form of this virus still circulates as seasonal flu and is associated with severe illness in older people.

2009 H1N1 Pandemic: Formally known as "swine flu," this was the first pandemic of the 21st century and spanned April 2009 through August 2010. The 2009 H1N1 virus had not previously been known to cause infections in humans and contained a unique combination of genes from human, swine, and avian influenza A viruses. Children, young adults, and pregnant people were the most affected, while older adults seemed to have some immunity from exposure to H1N1 strains before 1957. The impact of the virus on the global population was less severe than previous pandemics. It is estimated that between 151,000-575,000 people worldwide died during the pandemic. A form of this virus still circulates as seasonal flu.

Which virus will cause the next pandemic?

No one can predict which virus strain will cause the next pandemic, how rapidly the disease will spread, or how severe it will be. It is uncertain which population groups will be at the highest risk of disease and death.

The World Health Organization (WHO) has developed a list of priority diseases that pose the greatest public health risk due to their epidemic potential and/or their lack of available vaccines/treatments. Currently, the list includes: COVID-19, Crimean-Congo haemorrhagic fever, Ebola virus disease, Marburg virus disease, Lassa fever, Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome (SARS), Henipavirus diseases, Rift Valley fever, Zika virus, and "Disease X." "Disease X" represents a disease caused by a pathogen currently unknown to cause human disease.

What we do know

As seen with COVID-19, pandemics can disrupt all aspects of life. Business may be significantly impacted due to absenteeism, as employees fall sick or have to care for sick relatives. Schools may be temporarily closed, mass gatherings may be cancelled, and government authorities may impose travel restrictions.

Flu pandemics spread in waves. Waves may last weeks to months. Quarantines and other public health interventions may slow but are unlikely to prevent global spread. It may take months to years to develop new vaccines and treatments.

Pandemic planning

Pandemic planning may mitigate some of these impacts. Whilst planning for the next pandemic is critical and even mandatory for some industries such as healthcare and essential services, every organisation is encouraged to undertake a risk assessment, and ensure business continuity plans encompass the pandemic threat.

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