The Novel Coronavirus: What Are Novel Viruses, and How Do They Impact Public Health?

As we learn more about SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19) and is often referred to as a “novel coronavirus,” it is important to understand what makes this virus unique and what is meant by the term “novel.”

There are hundreds of different coronaviruses, most of which are found in animals such as pigs, camels, bats, and cats. But they can sometimes jump from animals to humans. When they do, they can cause illnesses that affect the upper respiratory tract (or upper breathing airways) — like the common cold, cough. 

It’s very rare that animal coronaviruses infect people and then spread between people.  However, three of the seven coronaviruses known to affect humans, which now includes SARS-CoV-2, have emerged from animals over the last two decades, and they’ve caused serious, widespread illness and death.

What does “novel” mean in medicine and virology?

The word “novel” originated from the Latin word “novus,” which means “new.” In medicine, “novel” usually refers to a virus or bacterial strain that was not previously identified. COVID-19 is a new disease, caused by the novel, or new, coronavirus SARS-CoV-2 that was not previously seen in humans.

What is a novel coronavirus, specifically?

Coronaviruses are a family of viruses named for the crown-like spikes on their surface. The word “corona” itself means “crown.” Although most coronaviruses are found in animals, the first human coronaviruses were identified in the mid-1960s, and seven, including SARS-CoV-2, are known to affect humans today. When animal coronaviruses evolve and are able to infect humans, these viruses are considered to be novel. Over time, these viruses change to be able to attach to different host cells, allowing them to enter the cells of new species. Since these viruses had not been seen before in humans, scientists and researchers must learn how the virus infects human cells and causes disease in order for them to develop potential treatments and vaccines.

COVID-19 is caused by a different coronavirus than those that cause the common cold. Four of the seven human coronaviruses typically cause mild to moderate illness and account for 10% to 30% of upper respiratory tract infections in adults. The other three, including SARS-CoV-2, can cause more serious respiratory illness. More on this below.

What about novel influenza (flu) viruses?

When you’ve heard of novel viruses in the past, it may have been in the context of novel influenza (flu) viruses, and not coronaviruses. We have seasonal influenza type A and type B viruses (influenza A and B viruses) that appear during each year’s cold and flu season, but there are also novel influenza A viruses that are not seasonal. Just like novel coronaviruses, these generally circulate among animals but have caused outbreaks in humans. 

Those of most recent concern include avian influenza A viruses (bird flu) that humans get from exposure to infected poultry, and swine/variant influenza A viruses (swine flu) that humans get from exposure to infected pigs. A significant concern of these novel influenza A viruses is their ability to spread from person to person, potentially causing a pandemic as we see today with SARS-CoV-2.