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
One head is good, but two ones are better.
A wolf is fed by his legs
A bird is visible by its flight.
The apple never falls far from the tree.
Get your sleigh ready in summer and your (horse-drawn) cart in winter.
There are no friends for taste and color.
Put your trust in God, but don't make mistakes yourself
Do not chop the branch you sit on