Viral infections are illnesses caused by a virus rather than bacteria or fungi. Many viral infections can cause skin rashes, called exanthems. Most clear up on their own, but some require medication.

Head colds are very contagious. When a person with a head cold sneezes or coughs, droplets that contain the virus can travel through the air and reach other people who could contract the virus.

Influenza virus is an infectious agent belonging to the virus family Orthomyxoviridae that causes a respiratory tract infection (influenza or 'flu') in vertebrates. There are three main species ...

Viral evolution refers to the heritable genetic changes that a virus accumulates during its life time, which can arise from adaptations in response to environmental changes or the immune response ...