Mumps is a viral infection first described by Hippocrates that in its classical form causes acute parotitis and, less frequently, orchitis, meningitis and pneumonia.
Poliovirus is highly contagious and infected individuals shed virus in the faeces and from oral secretions, thus the mode of transmission is person-to-person, both via the faecal-oral and the oral-oral routes.
Smallpox was a systemic disease, officially eradicated since 1979 (WHO), caused by infection with the Variola major virus, whose only reservoir was infected humans.