With accent marks:
Дурно́й приме́р зарази́телен.
A bad example is contagious.
Bad habits and wrong views of one person very often “stick” to other people.
The proverb is used to talk about a person who, without any thinking and hesitation, adopts bad habits of others.
Other Russian proverbs
We don't appreciate what we have but we cry when we lose it.
Crowded, but not aggrieved.
Appetite comes with eating.
Оne sees the mote in another's eye and ignores the log in his own.
Eggs don't teach the chicken.
Start taking care of the dress while it's new, and of your honor while you are young.
Without labor, you can not even catch a fish in the pond.
The quieter you go, the further you'll get.