A communicable disease is
The diseases which are transmitted from one person to another or from reservoir to susceptible person are called communicable diseases.
Diphtheria is an infection caused by the bacterium Corynebacterium diphtheria. Symptoms include a sore throat, fever, barking cough, a grey or white patches develop in the throat. Diphtheria is usually spread between people by direct contact or through the air. It may also be spread by contaminated objects.
Diphtheria is a communicable disease because it can be transmitted from one person to another through droplet infection.
So, the called as 'Diptheria'.