As the deadly COVID-19 outbreak spreads to Iran, Italy and South Korea, health authorities fear the contagious disease is on the brink of evolving into a global pandemic.
As of Monday, more than 78,800 cases have been confirmed globally, and 2462 people have died – the vast majority in China.
Foreign governments have enforced quarantine for infected people and issued travel bans on people leaving China.
But the spread of the disease is showing no signs of slowing down.
The World Health Organisation (WHO) has so far described the novel coronavirus as an epidemic affecting several countries.
The risk level could soon be elevated to pandemic status as the number of nations grappling with the sickness rises.
How does an outbreak, epidemic and pandemic differ?
What is an outbreak?
An outbreak is a sudden spike in the number of cases of a disease.
It can happen in a single community, region or several countries.
The most common outbreak is influenza, known as the flu, which occurs almost every year during winter – even in highly developed countries like Australia.
Despite huge leaps forward in medicine, influenza continues to infect people because the virus is able to evolve just enough to evade human immune systems.
For thousands of people, especially the elderly or young children, common influenza is deadly.
Typically, seasonal flu is thought to cause about 400,000 deaths each year globally.
In some unique situations, a single case of an infectious disease can be considered an outbreak if it is rare, such as rat-bite fever, or has serious public health implications, like anthrax – a naturally occurring bacteria that is used as a biological weapon.
What is an epidemic?
An epidemic occurs when an infectious disease spreads rapidly to a large number of people in a population.
Put simply, an epidemic is a more serious outbreak.
The outbreak of severe acute respiratory syndrome (SARS) from 2002 to 2003 is considered an epidemic because it claimed the lives of nearly 800 people around the world.
Like COVID-19, SARS is thought to be an animal virus that first infected humans in China, in the Guangdong province.
The spread of the gruesome Ebola disease in West Africa from 2014 to 2016 is another example of an epidemic.
The outbreak started in Guinea and then moved across land borders to Sierra Leone and Liberia, killing more than 11,300 people.
What is a pandemic?
A pandemic is a global disease outbreak that is difficult to control.
It differs from an outbreak or epidemic because it infects a greater number of people across multiple continents.
A pandemic is often caused by a new virus, or a new strain of virus, that has not circulated among people for a long time.
Humans usually have little to no immunity against it, meaning the virus is able to spread quickly from person to person worldwide.
Pandemics cause many more deaths than epidemics, and they often create other problems like social disruption and economic loss.
One of the world’s worst pandemics in human history was the Plague, also known as the Black Death, which killed an estimated 75 to 200 million people in Eurasia from 1347 to 1351.
Another devastating pandemic was the Spanish flu between 1918 and 1919 that wiped out between 20 and 50 million people.
