Coronavirus: the definitions of pandemic and epidemic - and why it matters
Covid-19 outbreak declared a pandemic by World Health Organization after it spreads to 125 countries
The World Health Organization (WHO) has officially declared the new coronavirus outbreak a pandemic after the number of cases outside China soared in recent days.
There have now been more than 126,000 cases reported across 125 countries and territories. More than 4,600 people have died, with around 1,470 of these fatalities outside China, where the outbreak began.
At a news conference on Wednesday, Tedros Adhanom Ghebreyesus, the director-general of WHO, said: “We are deeply concerned both by the alarming levels of spread and severity, and by the alarming levels of inaction. We have therefore made the assessment that Covid-19 can be characterised as a pandemic.”
So what does this mean?
Pandemic vs. epidemic
The US Centers for Disease Control and Prevention defines an epidemic as “an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area”. A pandemic, on the other hand, “refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people”.
For example, swine flu, or H1N1, was declared a pandemic by WHO in 2009.
Brian Labus, assistant professor of epidemiology and biostatistics at the University of Nevada, Las Vegas, notes that the term pandemic does not describe a disease’s severity.
“Because of their wide geographic distribution, pandemics usually affect a large number of people,” he writes in an article on The Conversation. “While we usually think of pandemics in relation to serious, life-threatening diseases, even outbreaks of mild diseases could cross borders and become pandemics.”
WHO’s website explains that for a pandemic to be declared, at least one other country in a different region to the original source nation - in this case, China - must have a “community level outbreak”, and “human-to-human spread of the virus” must have occurred in at least two countries in one region.
Seven countries outside China have now reported at least 1,000 cases, with Italy the second-worst affected nation, with more than 12,000 known patients and 827 deaths.
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Significance of terminology
Even when an outbreak is declared a pandemic, “the terminology doesn’t change anything about the severity of the disease or how we are responding”, says Labus on The Conversation.
And the risk to individuals will not change because of the terminology. “Even if an outbreak is spreading worldwide, how it is spreading locally and how people respond is what determines your risk,” he says.
Ghebreyesus said WHO had been cautious in declaring a pandemic because the word, “if misused, can cause unreasonable fear, or unjustified acceptance that the fight is over”.
He echoed Labus in saying that the terminology does not change the threat or what countries should do to respond, and added: “Let me give you some other words that matter much more… Prevention. Preparedness. Public health. Political leadership. And most of all, people.”