We have just witnessed a pandemic the like of which none of us has ever experienced. But what exactly are pandemics and have they previously been as severe as Covid-19?
The word pandemic literally means “across the people” and refers to a disease which spreads over a large distance, not just in a localised region. An infectious disease which spreads locally is known as an epidemic. Infections which have limited spread between people because most of their neighbours are immune or the germs have low infectivity are known as endemic. Infections can also be endemic because of special features of the environment where people live. For example malaria is endemic to countries with a hot climate and stagnant pools where a particular type of mosquito can thrive.
We are currently witnessing a pandemic the like of which none of us has ever experienced. But what exactly is a pandemic and have they been as severe as this in the past?
The word pandemic literally means “across the people” and refers to a disease which spreads over a large distance, not just in a localised region. An infectious disease which spreads locally is known as an epidemic. Infections which have limited spread between people because most of their neighbours are immune or the germs have low infectivity are known as endemic. Infections can also be endemic because of special features of the environment where people live. For example malaria is endemic to countries with a hot climate and stagnant pools where a particular type of mosquito can thrive.
Pandemics in the past were often referred to as plagues. In a historical context, plague does not necessarily signify what we mean by the word today. Many diseases once prevalent in the UK have disappeared in our lifetime. Smallpox has been completely eradicated across the globe and polio is only present in a small number of countries where there is a poor uptake of vaccination.
Other diseases like the sweating sickness in the 16th century vanished long before we were able to recognise its cause. New infections can emerge; examples in our own time are AIDS, New Variant CJD and coronavirus which is causing the current pandemic.
Pandemics in the past were often referred to as plagues. In a historical context, plague does not necessarily signify what we mean by the word today. Many diseases once prevalent in the UK have disappeared in our lifetime. Smallpox has been completely eradicated across the globe and polio is only present in a small number of countries where there is a poor uptake of vaccination. Other diseases like the sweating sickness in the 16th century vanished long before we were able to recognise its cause. New infections can emerge; examples in our own time are AIDS, New Variant CJD and coronavirus which is causing the current pandemic.
Many circumstances contribute to the rise and fall of pandemics. There may be changes in climate or in the host population of those infected. The infectious agents, particularly viruses, can mutate and become more or less virulent. There may be cross-transfer of infectious agents from other species when humans and animals move closer to each other. Cross immunity with other less virulent infections may lead to protection as demonstrated by cowpox providing protection against smallpox. Changes in behaviour patterns of human communities may occur, e.g. improved sanitation, new farming methods and medical interventions like vaccination and antimicrobial drugs. Overpopulation, crowding, war and famine make dissemination of contagious diseases more likely and faster global interchange of goods and people can rapidly disseminate a disease around the world.
Article by Dr. Roger Rolls.
Find out more about pandemics in Bath by following the section links below.