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
Being a guest is good, but being at home is better.
We don't appreciate what we have but we cry when we lose it.
Don’t wave your fists after the fight.
Live for a century, learn for a century, but die being a fool anyway.
Better to see once than hear a hundred times.
You can't help grief with tears.
The morning is wiser than the evening.
Your own shirt is closer to your body.