Words Ended with '-demic': Pandemic, Epidemic, Endemic, Twindemic, and Infodemic

This year during the COVID-19, we hear enough words ended with '-demic', some are old and some are new. A usual saying is that "the epidemic (or outbreak) is inevitable, but the pandemic is optional".

An epidemic is defined as “an outbreak of disease that spreads quickly and affects many individuals at the same time.” According to the CDC, "Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area."

Epidemics occur when an agent and susceptible hosts are present in adequate numbers, and the agent can be effectively conveyed from a source to the susceptible hosts. More specifically, an epidemic may result from:

• A recent increase in amount or virulence of the agent,
• The recent introduction of the agent into a setting where it has not been before,
• An enhanced mode of transmission so that more susceptible persons are exposed,
• A change in the susceptibility of the host response to the agent, and/or
• Factors that increase host exposure or involve introduction through new portals of entry.

A pandemic is a type of epidemic (one with greater range and coverage), an outbreak of a disease that occurs over a wide geographic area and affects an exceptionally high proportion of the population. Pandemic refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people. WHO simply defined "A pandemic is the worldwide spread of a new disease."

While a pandemic may be characterized as a type of epidemic, you would not say that an epidemic is a type of pandemic.

WHO classifies the pandemic as six phases + post-peak period and post-pandemic period and each phases should require different actions. 

The WHO is responsible for announcing the emergence of a new pandemic based on how the spread of the disease fits into the following 6 phasesTrusted Source:

• Phase 1. Viruses circulating among animal populations haven’t been shown to transmit to human beings. They’re not considered a threat and there’s little risk of a pandemic.
• Phase 2. A new animal virus circulating among animal populations has been shown to transmit to human beings. This new virus is considered a threat and signals the potential risk of a pandemic.
• Phase 3. The animal virus has caused disease in a small cluster of human beings through animal to human transmission. However, human to human transmission is too low to cause community outbreaks. This means that the virus places humans at risk but is unlikely to cause a pandemic.
• Phase 4. There has been human-to-human transmission of the new virus in considerable enough numbers to lead to community outbreaks. This kind of transmission among humans signals a high risk of a pandemic developing.
• Phase 5. There has been transmission of the new virus in at least two countries within the WHO regionTrusted Source. Even though only two countries have been affected by the new virus at this point, a global pandemic is inevitable.
• Phase 6. There has been transmission of the new virus in at least one additional country within the WHO region. This is known as the pandemic phase and signals that a global pandemic is currently occurring.

Endemic refers to the constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area. Endemic is a characteristic of a particular population, environment, or region. Examples of endemic diseases include chicken pox that occurs at a predictable rate among young school children in the United States and malaria in some areas of Africa. The disease is present in a community at all times but in relatively low frequency. An endemic disease may become pandemic - for example, HIV infection/AIDS used to be endemic in sub-Saharan Africa region and grown to pandemic in 1980's. 

Hyperendemic refers to persistent, high levels of disease occurrence.

A twindemic is the new word proposed this year and refers to the possibility of a severe flu season coinciding with a surge in COVID-19 cases. Even a mild flu season is concerning, given that the inevitable serious cases of the flu tax the medical system each year.

An infodemic is an overabundance of information, both online and offline. It includes deliberate attempts to disseminate wrong information to undermine the public health response and advance alternative agendas of groups or individuals. Mis- and disinformation can be harmful to people’s physical and mental health; increase stigmatization; threaten precious health gains; and lead to poor observance of public health measures, thus reducing their effectiveness and endangering countries’ ability to stop the pandemic.

Misinformation costs lives. Without the appropriate trust and correct information, diagnostic tests go unused, immunization campaigns (or campaigns to promote effective vaccines) will not meet their targets, and the virus will continue to thrive.

References: 

• Wood on Words: Getting to know your ‘-demics’ is all academic
• Managing the COVID-19 infodemic: Promoting healthy behaviours and mitigating the harm from misinformation and disinformation
• 'Pandemic' vs 'Epidemic' - How they overlap and where they differ
• Experts Warn of a Possible 'Twindemic'—Here's What That Means
• CDC: Epidemic Disease Occurrence
• CDC: Glossary of Epidemiology and Public Health