and are two important families of RNA viruses that cause a range of human diseases. From the to global pandemics, these viruses have significant impacts on public health and society.
Their distinct structures and replication mechanisms lead to diverse clinical outcomes. Understanding their biology, epidemiology, and management strategies is crucial for effective disease control and future pandemic preparedness.
Picornavirus and Coronavirus Structure
Structural Characteristics
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Picornaviruses consist of small, non-enveloped viruses with positive-sense, single-stranded
Size ranges from 22-30 nm in diameter
Genome length approximately 7.2-8.4 kb
Coronaviruses comprise larger, enveloped viruses with positive-sense, single-stranded RNA genome
Size ranges from 80-120 nm in diameter
Genome length approximately 26-32 kb (largest among RNA viruses)
Picornavirus exhibits icosahedral symmetry composed of four structural proteins (VP1-VP4)
VP1, VP2, and VP3 form the outer surface
VP4 located internally, interacts with the RNA genome
Coronavirus contains spike (S), envelope (E), and membrane (M) proteins
S protein forms distinctive crown-like appearance (corona)
Helical nucleocapsid encases the RNA genome
Replication Mechanisms
Picornavirus replication occurs entirely in the cytoplasm
Involves formation of a single polyprotein cleaved into functional proteins
Utilizes internal ribosome entry site (IRES) for cap-independent translation initiation
Coronavirus replication produces nested sets of subgenomic mRNAs
Employs cap-independent translational enhancer (CITE) for translation initiation
Replication complex associates with double-membrane vesicles
Pathogenesis and Infection Outcomes
Picornaviruses typically cause lytic infections leading to cell death
Enter host cells through specific receptors (ICAM-1 for )
Rapid replication cycle (6-8 hours) results in cell lysis and virus release
Coronaviruses induce both lytic and persistent infections
Entry mediated by S protein binding to host cell receptors (ACE2 for )
Can establish persistent infections in certain cell types (neurons, kidney cells)
Picornavirus pathogenesis often involves entry through gastrointestinal or respiratory tract
Local replication followed by potential systemic spread ()
Neurotropic strains (poliovirus) can invade the central nervous system