Communicable diseases spread from one to another through air, water, contact, blood. There are many. Some of them are:
Tuberculosis TB - spreads through the infectious bacteria through air.
Viral infection - through air infected by another (fevers)
conjunctivitis - eye infection - viral through air
HIV/AIDs - through blood mixing, transfusion
Dengue fever transmitted by mosquitoes
Chikengunea is transmitted by the mosquitoes
amebiosis - through water