Coronaviruses: important emerging human pathogens

Abstract

The identification of Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012 reaffirmed the importance of understanding how coronaviruses emerge, infect, and cause disease. By comparing what is known about severe acute respiratory syndrome coronavirus (SARS-CoV) to what has recently been found for MERS-CoV, researchers are discovering similarities and differences that may be important for pathogenesis. Here we discuss what is known about each virus and what gaps remain in our understanding, especially concerning MERS-CoV.

FIG 1

(A) Genome structures of SARS-CoV and MERS-CoV. The single-stranded positive-sense coronavirus genomes encode the structural proteins (blue) membrane (M), spike (S), envelope (E), and nucleocapsid (N), two replicase polyproteins (purple), ORF1a and ORF1b, and unique accessory proteins (red) that perform important functions in coronavirus replication and pathogenesis, such as blocking the innate immune signaling pathway. (B) Transmission routes. SARS-CoV transmission is thought to be from bats harboring SARS-like viruses to palm civet cats, which infected humans. SARS-CoV could also have been transmitted from bats to humans directly. MERS-CoV is thought to be transmitted from camels to humans, with the possibility that at some point bats infected camels. The dashed line identifies a low-level transmission event, the thin solid line identifies a potential transmission event, and the thick solid line identifies a probable transmission event.