Structure & Property

Transmission

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment

Family: picornavirus

Size: 22-30nm

Genome: single stranded RNA, positive polarity.

Nucleocapsid: icosahedral

More than 100 serotypes.

Replicate better at 33 than at 37 degrees

Acid-labile: killed by gastric acid when swallowed.

Host range: humans and chimpanzees.

Transmitted directly from person to person via aerosols of respiratory droplets.

Transportation of respiratory droplets on hands or surfaces by fingers to nose and eye.

Occur worldwide, causing disease in fall and winter particularly.

Main cause of common cold.

Affect primarily the nose and conjunctiva rather than lower respiratory tract.

Rarely cause lower respiratory tract disease as it grow poorly at 37 degrees.

Portal of entry is upper respiratory tract and infection is limited to that region

Incubation period: 2-4 days

Sneezing

Nasal discharge

Nasal obstruction

Sore throat

Cough

Headache

Complications:

- sinusitis

- otitis media

Isolation:

- mouth washings

- nasal secretions

Tissue culture:

- human embryo lung

- monkey kidney cells

Serologic tests are not done.

Respiratory IgA shows the main protective effect against reinfection with particular serotype responsible.

No antiviral therapy available.