Coronavirus: Is Covid-19 an epidemic or a pandemic? What's the difference?

During a recent daily media briefing, the World Health Organisation's Director-General Tedros Adhanom Ghebreyesus revealed that although Covid-19 has spread worldwide, the WHO was yet to consider it a 'pandemic'.

"Our decision about whether to use the word 'pandemic' to describe an epidemic is based on an ongoing assessment of the geographical spread of the virus, the severity of disease it causes and the impact it has on the whole society," Ghebreyesus said during the briefing.

KT explains why the epidemiological terminology, or how we describe the amount a particular disease is present in a community, is important.

According to the US Centers for Disease Control and Prevention, an 'epidemic' refers to an often sudden increase in the number of cases of a disease above what is normally expected in the population of that area. The commonly used word 'outbreak' carries the same definition, but is often used for a more limited geographical area.

For example, we could say that there was an outbreak of the coronavirus epidemic in Wuhan.

One of the most famous epidemics was the Western African Ebola virus epidemic of 2013, which was one of the most widespread outbreaks of the Ebola virus disease in history, claiming the lives of over 11,000 people.
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Because the Ebola epidemic was mainly confined to Western African countries such as Liberia and Sierra Leone, with a few cases being reported outside the region in medical workers, it was never classified as a 'pandemic'.

A pandemic refers to an epidemic that has spread over several countries or continents, usually affecting an extremely large number of people, different from an epidemic in that it reaches a much larger scale.

"The word pandemic comes from the Greek 'pandemos', which means everybody. Demos means population. Pan means everyone. So 'pandemos' is a concept where there's a belief that the whole world's population will likely be exposed to this infection and potentially a proportion of them fall sick," said Dr. Mike Ryan, WHO's Executive Director of Health Emergencies Programme.

"What we don't understand yet in Covid-19 are the absolute transmission dynamics. So we're in a phase of preparedness for a potential pandemic," he said.

Other epidemiological classifications include 'endemic', which refers to the constant presence of a disease in a geographical population. For example, malaria is an endemic in the WHO African Region, with 94 per cent of worldwide malaria deaths occurring in the region.

'Hyperendemic', on the other hand, refers to persistently high levels of a disease in an area, such as HIV being hyperendemic in Southern Africa, where as many as 1 in 5 adults has the disease.

To stop diseases from reaching pandemic levels, the CDC proposes a four-programme for public health systems to follow, which include:

> Surveillance systems to rapidly detect and report cases
> Laboratory networks to accurately identify the cause of illness
> A trained workforce to identify, track, and contain outbreaks
> Emergency management systems to coordinate an effective response

"Let's focus on what we can do and what we need to do, which is prepare," said Dr. Mike Ryan on what WHO was doing to prevent coronavirus from reaching pandemic levels.

"When we mean prepare, we mean prepare to detect cases, prepare to treat cases, prepare to follow contacts, prepare to put in place adequate containment measures."