Chapter 57 Picornaviruses - Rhinoviruses Medical Microbiology Chapter 57 Picornaviruses - Rhinoviruses

Rhinoviruses Pico-rna-viruses Structure: Rhinoviruses cause the common cold Structure: Naked virus Single-stranded RNA genome (linear) Plus-strand of RNA (essentially an mRNA) Contains 7200-8450 bases with a poly-A tail The genome alone is able to cause infection Human Rhinoviruses consist of at least 100 different serotypes Importance in cold recurrence Vaccine?

Rhinoviruses Infection may be initiated by as few as 1 virus Attachment occurs through the ICAM-1 molecule on epithelial cells Viral replication shuts down normal cellular RNA and protein synthesis This is the primary cause of pathology Infected cells release inflammatory chemicals which stimulate nasal secretions (“runny nose”) Viruses are shed in nasal secretions (500-1000 viruses/ml)

Rhinoviruses The viruses replicate poorly at above 33º C Confined to upper respiratory tract Implications for cold weather infections? Transmission – virus can be passed by aerosols or contact with fomites (naked virus) Hands seem to be the major mechanisms of transmission Box 57-5 and 57-6 Info. from other text