The image of a coronavirus is easily recognizable due to its bumpy topped spikes. These spikes earned the family of viruses their name, which comes from the corona, or crown, that encircles the sun.
Coronaviruses are zoonotic, which means they can be transmitted from animals to humans. Coronaviruses have been found in birds and in numerous mammals, including bats, camels, cows, civet cats, and even domestic cats and dogs. In fact, researchers have identified several coronaviruses circulating in animal populations that haven’t made the leap to humans.
THE COMMON COLD
What’s known as a “cold” is a respiratory viral infection that can be caused by any number of viruses. Most of these respiratory viruses are familiar to scientists, but some have yet to be identified. Four coronaviruses are prevalent in humans, causing 10–15% of all common colds.1
Researchers discovered the first human coronaviruses in the mid-1960s. These are called coronavirus OC43 and coronavirus 229E.2 The next cold-causing coronavirus, NL63, wasn’t discovered until 2004, and the fourth, HKU1, was identified in 2005.2
While it’s not clear when these coronaviruses first entered the human population, or from which sources, NL63 and 229E mostly likely came from bats, while OC43 and HKU1 probably originated in rodents.1
These four coronaviruses mostly cause garden-variety colds that can be unpleasant but are generally considered mild illnesses. They’re often accompanied by symptoms like coughing, sneezing, sore throat, and nasal congestion.
SERIOUS CORONAVIRUS OUTBREAKS
In late 2002, a new coronavirus emerged that was much more serious and deadly than previously known coronaviruses. This virus, ultimately named Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV), could cause a critical infection that progressed to pneumonia and respiratory failure. About 25% of infected patients required intensive care,1 and roughly 11% died of the disease.3 This is a much higher case fatality rate than seems to be caused by COVID-19. (Estimates for the case fatality rate for COVID-19 are preliminary and vary widely between countries and researchers. In early September, Johns Hopkins University pegged the case fatality rate in the United States at 3.0%.)4
However, SARS-CoV seemed to be more pathogenic and spread less effectively than the 4 known common cold-causing coronaviruses. Transmission of SARS-CoV appeared to require prolonged contact with an infected person, resulting in many outbreaks in healthcare settings.5
The Middle East Respiratory Syndrome Coronavirus (MERS-CoV) arrived on the scene a decade later, in 2012. While SARS-CoV most likely entered the human population from civet cats, MERS-CoV transmits from dromedary camels to people.6
MERS-CoV is even more deadly than SARS-CoV, with a mortality rate of 35%.2 However, MERS-CoV is not easily transmissible from person to person, much like SARS-CoV. Instead, it survives in dromedary camels and makes repeated jumps to people, “producing single infections or short transmission chains that eventually resolve, with no adaptation to sustained transmission.”7
MERS-CoV infections can be mild, but they can also lead to severe pneumonia, respiratory distress, septic shock, and multi-organ failure.1 More than 2,500 cases of MERS-CoV have been reported in 21 countries, although most cases occur in the Middle East.3
https://www.biofiredx.com/blog/history-of-coronavirus/
