Emerging infectious diseases” are those that are rapidly increasing in incidence or geographic range.  Most are zoonotic, entering the human population from other animal species.  None exemplifies this better than the coronaviruses.  The first three decades of the 21st Century have seen three zoonotic coronaviruses introduced into the human population.  The first zoonotic human coronavirus, SARS-CoV (Severe Acute Respiratory Syndrome coronavirus), first appeared in China in late 2002, and spread worldwide from a single patient in Hong Kong in February 2003. When the epidemic was ended, in June 2003, there had been 8,098 cases (with 774 deaths), in 19 countries, including mainland China, Taiwan, Vietnam, Singapore, and Canada.  The natural host of SARS-CoV was a small bat (Rhinolophus), and the virus probably reached humans through live animal markets in south China.  Further investigation identified a number of related viruses in the same and other bat species.  A decade later, in 2012, Middle East Respiratory Syndrome (MERS) coronavirus appeared, with clinical presentation similar to SARS.  The epidemic is still ongoing, with over 2,500 cases (> 870 deaths, case-fatality ratio ~34%); approximately 80% of the cases are in Saudi Arabia.  Healthcare associated transmission accounted for most cases of SARS and MERS.  In late 2019, patients were hospitalized with atypical pneumonia in Wuhan, China.  The cause was identified as a coronavirus, subsequently named SARS-CoV-2 because of its close relationship to SARS (the disease is called Coronavirus Disease 2019, abbreviated as COVID-19).  Unlike SARS, SARS-CoV-2 could transmit readily from person to person by the respiratory route, allowing it to reach pandemic proportions.  With both SARS and SARS-CoV-2, the infections came to global attention through ProMED-mail (a system for Internet reporting and discussion of emerging infections).  The global response galvanized by SARS in 2003 makes an interesting comparison with the current response to SARS-CoV-2.

Learning Objectives:

1. Discuss 2 similarities and 2 differences between SARS-CoV-2 (COVID-19) and the earlier zoonotic coronaviruses (SARS and MERS-CoV)

2. Evaluate the likelihood of future pandemic coronaviruses