Berchmans Honors Blog: Where Else Have We Seen Coronaviruses?

Where Else Have We Seen Coronaviruses?

Recently, the word “coronavirus” has been used to describe the novel respiratory virus, COVID-19 (the disease) or SARS-CoV-2 (the virus) that has caused more than 4.6 million deaths as of September 2021. However, coronaviruses themselves aren’t novel and have infected humans as recently as the 1960s. In fact, most of the human coronaviruses (HCoV) were considered a nuisance prior to the discovery of SARS-CoV, MERS-CoV, and especially SARS-CoV-2.

The first of these zoonotic coronaviruses were HCoV-OC43 (Organ Culture 43) and HCoV-299E (code name of the specimen), which were discovered in the 1960s, the era of the invention of the electron microscope. Since they only caused mild cold-like symptoms, most scientists decided to focus their research on other diseases, although these viruses remained the center of research for HCoV.

In 2003, a SARS-CoV (Severe Acute Respiratory Syndrome Coronavirus) strain was discovered in Asia. This coronavirus outbreak would not be like the previous ones, however. Although all coronaviruses cause respiratory disease, SARS-CoV was less common than its counterparts but had a greater case fatality rate with a total of 8,098 confirmed cases and 774 deaths in Asia, Europe, and the Americas.

More attention has been brought to the origin of SARS-CoV compared to the previous coronaviruses. Scientists have tried to track down the animal or animals SARS-CoV has come from, and the majority point to bats being a reservoir because evidence of coronaviruses have been found in their natural habitats. It is more likely, however, that an intermediary animal, such as a common mammal that humans come in contact with, helped pass along the virus from bats to humans.

The introduction of a new coronavirus with such a high death rate prompted scientists to not only look into the origin of the virus, but also to look for other HCoVs that could help them better understand the nature of coronaviruses. Scientists looked for patients with flu-like symptoms and found NL63 (Netherland 63) in 2004 and HKU1 (Hong Kong University 1) in 2005. These two viruses were very similar to their older counterparts; they all caused mild to modest illness in the upper respiratory tract and all four viruses contributed to 15-30% of colds in people. In fact, there is evidence that proves it is not atypical for a person to be infected with the same coronavirus twice, even with less than a year between infections.

Since 2004, there have been no more reported cases of SARS-CoV. However, not long after the SARS outbreak, a new coronavirus was discovered: MERS-CoV (Middle East Respiratory Syndrome Coronavirus). As the name suggests, this coronavirus originated in the Middle East but eventually made its way to Europe and Asia. There have been approximately 2,580 reported cases of MERS-CoV with a case fatality rate of about 35%, meaning that around 900 people have died from this virus. Unlike SARS-CoV, however, cases of MERS-CoV are still being reported in the Middle East. Most human cases were linked back to camel exposure, suggesting that camels act as the intermediary for the virus between bats and humans, although human-to-human transmission is possible but far less likely.

Both MERS-CoV and SARS-CoV were extremely deadly viruses with dangerously high case fatality rates, yet both were controlled and contained easily in contrast to the four common coronaviruses that only inflict minor illness but are nearly impossible to contain. However, SARS-CoV-2 uses the dangerous aspects from both virus types to create a virus with pandemic potential. Humans have already experienced the devastating effect of this virus, with its high transmissibility and case fatality rate of about 1.3% in May of 2020, although the statistics show an increase to about 2% currently.

It’s unlikely that we’ll see another coronavirus as devastating as SARS-CoV-2 anytime soon. However, the virus won’t simply “go away” like polio did when the vaccine was introduced. It is too widespread to be exterminated. The best that humanity can hope for is to reduce the disease severity so that living with the virus won’t be such a dangerous situation as 2020 has made it seem.