The History of Coronaviruses and Humanity

Several months into the COVID-19 pandemic, what we don’t know about COVID-19 still outweighs what we do know about the disease. Chinese researchers identified the causative virus as a novel coronavirus early in January 2020, making it the seventh known coronavirus to infect humans. Some coronaviruses circulate widely in humans, causing mild cold symptoms. Other coronaviruses have proven serious and deadly. How does the novel coronavirus fit into this picture?

WHAT IS A CORONAVIRUS?

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

THE COVID-19 PANDEMIC

The current pandemic was sparked by the newest coronavirus to move from animals to humans. This coronavirus was named the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), and it causes the disease known as Coronavirus Disease 2019 (COVID-19).

SARS-CoV-2, which appeared in China in late 2019, is highly contagious, much like the widespread cold-causing viruses. Unlike those viruses, it can lead to severe, life-threatening illness.

Physicians in China began noticing the new disease in December 2019, although the earliest cases are believed to have emerged in November of that year. By late December, China had recognized dozens of cases of the disease. The first death was reported on January 11, 2020. By early October 2020, the virus had infected more than 33 million people worldwide and led to more than 1 million deaths.⁸

Signs and symptoms of a SARS-CoV-2 infection range from mild, cold-like symptoms to fever, shortness of breath, and breathing difficulties. The most severe cases can lead to pneumonia, severe acute respiratory syndrome, and death.

SYNDROMIC RESPIRATORY TESTING

The signs and symptoms of a respiratory infection—whether it’s a cold, the flu, or COVID-19—can be similar and overlapping. That makes it impossible for a physician to know what’s making a patient sick without diagnostic results. Right now, anyone who comes down with a fever or cough is going to be concerned about COVID-19. But SARS-CoV-2 has been detected in respiratory samples less than 10% of the time during the COVID-19 pandemic.⁹

BioFire’s syndromic testing offers the ability to detect numerous pathogens with one, rapid test. The BioFire^® Respiratory 2.1 Panel identifies 22 respiratory pathogens, including SARS-CoV-2, with results in about 45 minutes.

Humanity will likely be living with COVID-19 for years to come—hopefully mitigated with effective treatment and vaccines. When you throw the annual flu season into the mix with COVID-19, along with handfuls of other respiratory viruses, the importance of syndromic testing becomes clear.

Learn more about BioFire’s syndromic reagent panels.

References

1. Chaplin, S. Prescriber. May 2020. 31(5):23-28.
2. Williams, S. The Scientist. June 2020. Retrieved from: https://www.the-scientist.com/news-opinion/a-brief-history-of-human-coronaviruses-67600
3. McLeod, V. Lab Health and Safety. March 2020. Retrieved from: https://www.labmanager.com/lab-health-and-safety/covid-19-a-history-of-coronavirus-22021
4. Johns Hopkins University. Coronavirus Resource Center: Mortality Analyses. Accessed on Sept. 8, 2020. Retrieved from: https://coronavirus.jhu.edu/data/mortality.
5. Paules CI, et al. JAMA. 2020;323(8):707–708.
6. Fani M, et al. Future Virol. 2020;10.
7. Andersen K., et al. Nature Medicine. April 2020. 26:450-455.
8. Johns Hopkins University. COVID-19 Dashboard. Retrieved from: https://gisanddata.maps.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6
9. The COVID-19 Tracking Project. The Atlantic. Retrieved from: https://covidtracking.com/data