Manners are Infectious
Infectious means liable to be transmitted to people. In his essay "On Saying Please" Alpha of the Plough has very aptlycommented on good and bad manners as infectious. If the bad manners of one person influence others and make them rude and ill-tempered; the good manners of one person also affect others and make them polite and kind. The writer has propagated his view point with two examples.
The first example is of bad manners. A fellow did not say "please" to a lift-operator and was thrown of the lift by him. May be that fellow has had a quarrel with his wife on breakfast table. The wife might have been annoyed by the cook who might have been irritated on the behaviour of the house-maid. Thus due to one person's discourtesy, a chain action started and so many people were infected with it.
The second example is of good manners. A bus conductor on London routes was very nice and helpful to his passengers. He treated the blind, the old and the young ones carefully and lovingly. He even gave the writer a ticket when the writer boarded his bus without any money in his pockets. His civility radiated comfort, joy and peace. As a result his passengers could not help being nice and polite.
In short, the writer has rightly said that manners are infectious; whether they are bad or good. Like infections they travel from person to person leaving their bitter or sweet taste in the environment. They quickly spread from one person to another like a contagious disease. As we live in a society so the ways and manners of people are bound to affect others.