A pandemic is an epidemic (infectious disease outbreak) that spreads on a global scale. Pandemics usually occur when a new infectious disease emerges that can spread rapidly around the world.
The World Health Organization (WHO) declared the outbreak of COVID-19 a pandemic on 11 March 2020. This COVID-19 pandemic is the first caused by a coronavirus. (WHO)
A pandemic can occur when a new virus emerges and there is worldwide spread of the disease. Most people do not have immunity to a new virus. Viruses that have caused past pandemics usually come from animal viruses that have mutated to affect humans.
For a new virus to have pandemic potential it must meet three criteria:
- humans have little or no pre-existing immunity against the virus
- the virus causes disease in humans
- the virus can spread efficiently from person to person.
Previous pandemics include Spanish Influenza in 1918 or H1N1 Swine Flu in 2009. Only Type A influenza viruses have been known to cause influenza pandemics. This COVID-19 pandemic is the first caused by a coronavirus.
On 11 March WHO declared COVID-19 a pandemic. The WHO used this declaration to call for urgent and aggressive action. They noted that this is a pandemic that can be controlled. Both China and the Republic of Korea have significantly declining outbreaks.
The health impact of a pandemic on the community depends on how easily the virus can be spread between people (i.e. transmissibility) and the seriousness of the illness it causes (i.e. clinical severity). Healthcare systems can limit the impact on a community by slowing the spread of the infection between people and increasing the ability of the healthcare system to look after people who do get sick. NSW Health is putting a lot of effort into doing both of these things.