Emerging Animal Coronaviruses: First SARS and Now MERS

The first major pandemic of the new millennium that arose from southern China in 2002 was of zoonotic origin from wild game animals, called severe acute respiratory syndrome [SARS]. The culprit was determined to be a coronavirus of animal origin [SARS-CoV]. The discovery of the SARS-CoV, which caused an outbreak of >8000 people in >30 countries with fatality of about 10%, resulted in intense search for novel coronaviruses with potentially high pathogenicity. Ten years later after the SARS pandemic, another novel coronavirus crossed the species barrier from bats to humans through an intermediate camel host, to produce a severe lower respiratory infection labeled the Middle East respiratory syndrome [MERS]. A novel coronavirus [MERS-CoV] was first identified in September 2012, from patients who resided or traveled to Saudi Arabia. The MERS-CoV spread through contacts with camel and subsequently from human to human via droplet transmission. MERS cases occurred in several other countries including in Europe and the United States, mainly from residence or travel to the Arabian Peninsula, but was not of pandemic potential. However, in the spring of 2015, a MERS outbreak started in South Korea which was initiated by a returning traveler from Saudi Arabia, and subsequently secondary infection of over 186 local residents occurred. Recent estimate in May 2015 indicates that the MERS-CoV have afflicted 1167 patients with MERS worldwide with 479 deaths [41% fatality]. Thus MERS is more deadly than SARS but appears to be less contagious. However, unlike SARS which has not reappeared since 2002–2003, MERS-CoV have the potential to cause sporadic or local outbreaks for many years as the virus may now be entrenched endemically in dromedary camels of the Middle East.