Coronaviruses are a large family of viruses that usually cause mild to moderate upper-respiratory tract illnesses, like the common cold, in people. However, three times in the 21st century coronavirus outbreaks have emerged from animal reservoirs to cause severe disease and global transmission concerns.
There are hundreds of coronaviruses, most of which circulate among animals including pigs, camels, bats and cats. Sometimes those viruses jump to humans—called a spillover event—and can cause disease. Seven coronaviruses are known to cause human disease, four of which are mild: viruses 229E, OC43, NL63 and HKU1. Three of the coronaviruses can have more serious outcomes in people, and those diseases are SARS (severe acute respiratory syndrome) which emerged in late 2002 and disappeared by 2004; MERS (Middle East respiratory syndrome), which emerged in 2012 and remains in circulation in camels; and COVID-19, which emerged in December 2019 from China and a global effort is under way to contain its spread. COVID-19 is caused by the coronavirus known as SARS-CoV-2.
Thanks to research investments into the SARS and MERS outbreaks, NIAID scientists and grantees are better prepared to develop diagnostics, therapeutics and vaccines against COVID-19. Included in those projects are basic research to understand how the virus infects cells and causes disease; adapting platforms used to develop diagnostic tests and vaccines; and evaluating treatments such as broad-spectrum antivirals and potentially monoclonal antibodies.
In fact, within two weeks of the discovery of COVID-19, NIAID researchers had determined how the virus enters cells.
Why Are Coronaviruses a Priority for NIAID?
When SARS emerged from China in 2002 it swept across the globe—largely through air travel—causing deadly illness. More than 8,000 people fell ill and 774 died, numbers COVID-19 surpassed within two months. SARS drew the collective focus of researchers throughout the world. The disease disappeared in 2004, likely due to isolation and quarantine containment measures, and no cases of SARS have been reported since. In 2012, a new coronavirus emerged in the Middle East causing an illness similar to SARS. Again, researchers at NIAID and across the globe initiated studies to understand MERS-CoV and how to stop it. Research efforts from those two outbreaks—including development of a DNA vaccine candidate for SARS by NIAID’s Vaccine Research Center—have prepared scientists to quickly assess the severity and transmission potential of SARS-CoV-2, and to develop countermeasures.
How Is NIAID Addressing This Critical Topic?
When MERS emerged in 2012 and COVID-19 was identified in 2020, NIAID intramural and extramural scientists mobilized quickly to study the viruses, efforts which continue today. Key areas of investigation include basic research on their origins, how they cause disease, and developing animal study models, new treatments, and vaccines.
To learn about risk factors for coronaviruses and current prevention and treatment strategies visit the MedlinePlus coronaviruses site.
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Since its emergence in 2012, NIAID scientists have advanced their understating of how the virus causes disease. Work has shown that for MERS to infect a person, the virus enters cells using the spike, or S protein. After entering the cell, the virus delays the normal immune system response, allowing the infection to gain a foothold in the body. By the time the immune system recovers, the infection has progressed and become much harder to fight. Their research also shows that SARS and COVID-19 use a different protein than MERS uses to enter cells.
Tracking Coronavirus Transmission
Coronaviruses evolve quickly and have a long history of shifting between animal species, leading scientists to explore the origin of MERS and how it infects people. While many other coronaviruses in nature are not known to infect people, COVID-19, MERS, and SARS are notable for their ability to infect a variety of different species.
Therapeutics & Vaccines
NIAID-funded scientists are exploring ways to treat and prevent COVID-19 and MERS infections by working to develop new antibodies, drugs, and vaccines that block entry to cells or delay the immune system response. Other grantees are working to develop a live, attenuated MERS vaccine, which is a type of vaccine that contains a version of the living microbe that has been weakened in the lab so it cannot cause disease.