Some terms to know

 epidemic vs. pandemic – You have probably heard both words.  Covid-19 was initially called an “epidemic,” namely, a disease that had suddenly afflicted a large number of people in a particular area.  Eventually, as the virus spread around the world, Covid-19 was declared a “pandemic,” which is just an epidemic that has affected people on a much larger scale (a whole country or the whole world).

pathogens – a term used to refer to microorganisms (such as bacteria and viruses) that can cause diseases. 

epidemiology – a field of medical science that includes the study of what causes diseases and how they are spread among certain populations. (Epidemiologists don’t only study diseases, though; they look at any topics related to the health of a population.)

virulent – capable of causing severe illness

The World Health Organization (WHO) – a branch of the United Nations whose purpose it is to address global health issues, including the control of diseases.  The organization also oversees health education and research worldwide.

The Centers for Disease Control and Prevention (CDC) – a federal agency of the United States whose purpose it is to help prevent and respond to health threats that affect Americans. 

More about viruses and infectious diseases

– Viruses enter hosts (for example, human bodies), and replicate there.  The symptoms that result in the body that the virus now calls home, such as coughing and sneezing, are effective ways for the virus to travel from one host to another.  Because humans move around and interact with one another a lot, they are efficient carriers of viruses.  Everything from a handshake to a hug or even just an unintended and often unnoticed spray of virus-laden moisture from the mouth when talking can transport microbes from one person to another.

– Before modern times, when people didn’t know about the importance of sanitary practices, like washing one’s hands and keeping living and working environments clean, pathogens spread like wildfire, particularly through crowded cities.  Once sanitation improved and vaccines and antibiotics were developed, there was a dramatic drop in the spread of disease.

– However, this doesn’t mean we don’t have to deal with the spread of deadly pathogens anymore.  COVID-19 is just one current example.  Scientists remain vigilant about new infectious diseases, which are popping up faster and faster.  Sars and HIV are two recent examples. 

– The number of outbreaks in the world has increased threefold in the last 40 years.  There are several reasons for this.  First, there are simply more humans on the planet.  This means that people live more closely together, enabling viruses to spread with increasing ease.   Secondly, we are living with more livestock than ever before.  This is convenient for viruses, many of which might start off in the animals that we raise and then hop over to us.  Another reason infectious diseases are spreading more rapidly these days is that the world has become so interconnected.  People quickly travel from one corner of the Earth to another – and viruses travel with them.  Climate change has contributed to the rise in new diseases, too, because the range of animals, which carry deadly pathogens –  in particular insects – has greatly expanded.  Finally, so-called “vaccine hesitancy” has been on the rise, due to lots of misinformation, which has been spreading almost as quickly and as dangerously as viruses.  In 2019, the WHO called the growth of the “anti-vaccination movement,” one of the “top ten public health threats” facing humanity.

Other pandemics of the past and present

To date, about 5.8 million people have lost their lives to Covid-19.  How does this pandemic, which has changed so much for so many, compare to pandemics of the past? 

1) The 6th Century – The Plague of Justinian was probably caused by the Bubonic Plague, which was an infection that was spread among humans by fleas living on rats, mice, and other rodents.  Some 50 million people were killed during that pandemic – almost half the world’s population at the time.

2) The 14th Century – The Black Death was likely caused by the same pathogen that killed so many during the Plague of Justinian.  It is estimated that 75-200 million people died worldwide. 

3) 1918 – During the 1918 flu pandemic 50-100 million people lost their lives.  The disease sickened one in three people around the globe.

4) The 20th Century – Smallpox caused some 300-500 million deaths.  By 1980, it was the first disease to be completely eliminated, thanks to a vaccine.

5) HIV is still with us, and to this day, there is no vaccine to prevent its spread.  It has caused over 30 million deaths since 1982 and has so far infected 75 million people.