Two Coronaviruses, HCoV-229E and HCoV-OC43, causing generally mild respiratory tract infections in humans, were described in the XX c. Pandemic Coronaviruses were first discovered as late as in the XXI c.: SARS-HCoV in 2002 – causing severe respiratory tract infections (SARS) in China; MERS-HCoV in 2012 – circulating mostly on the Arabian Peninsula. The SARS epidemic ended in 2004 resulting in morbidity of > 8000 and > 770 deaths, while the MERS epidemic is still ongoing (> 2000 ill, > 700 deaths) although its intensity decreased. Both viruses are zoonotic and require at least two “host jumps” for the transmission of the infection to humans: for HCoV-SARS – from bat to palm civet and then to human; for HCoV-MERS – from bats to camels and subsequently to humans. Primary mode of transmission is droplet in close contact (< 1 m), but both viruses remain active in aerosol (up to 24 h), so infection can be also spread by air (ventilation). The ability for human-to-human transmission is higher for HCoV-SARS than for HCoV-MERS (8 generations vs. 4, respectively). Moreover, there are differences in genome structure and pathogenic mechanisms: different receptor, cell entry mechanism, different way of host response modulation (e.g. inhibition of IFNβ cascade), etc. Probably, these differences influence the overall manifestation of the disease in humans. Infection caused by HCoV-MERS might manifest itself as ARDS, a mild-mannered and asymptomatic disease. HCoV-SARS infections seem to be associated with severe disease only. In this paper, a comparison of the structure of these viruses, the mechanisms underlying their ability to cross the interspecies barrier and to multiply in the human body, including modulation of IFNβ cascade, as well as routes of infection transmission and symptoms caused, were presented.
1. Background. 2. Comparison of structure. 3. Transmission of infections. 3.1. Origin of the viruses. 3.2. Interspecies transmission. 4. Infections in humans. 5. Growth of the viruses in the human body. 5.1. Inhibition of interferon cascade. 6. Infections due to MERS- HCoV and SARS-HCoV. 7. Hospital outbreaks. 8. Summary
