Most types of conjunctivitis are caused by herpes simplex and adenovirus. Both these types can occur with respiratory infections and other symptoms related to cold like sore throat. On the other hand, if you wear unclean contact lenses, there is a chance you might develop bacterial conjunctivitis.
Both these viral and bacterial conjunctivitis are contagious as they can spread through indirect or direct contact with the liquid present in the infected person’s eye.