The common cold is a seasonal disease.
In over 50% of the cases, the common cold is caused by a Rhinovirus (of the family picoRNAvirus). This virus is a postive single stranded RNA non enveloped (but encapsulated) helicoidal virus, which means it can be directly interpreted by the cells ribosoms. It is stable in the presence of detergent and heat, but not acids. It replicates poorly in temperatures above 33c which is why it remains in the upper respiratory tract. It releases histamines, which cause the symptoms of the cold (and explains why their similar to allergies)[8].
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Common cold is caused by viruses