Young children who get Sars don't tend to have as serious symptoms as teenagers and adults, researchers have found.
Teenagers have trouble breathing, muscle pains and shivers.
But younger children have milder symptoms like a runny nose and a cough.
Good and bad news
They also recover more quickly than older people do.
Doctors don't know why this happens yet, but it's possible that kids have stronger immune systems to fight off 'childhood diseases'.
There's good and bad news about Sars around the world.
New cases
Possible first cases have been found in three new countries - Mongolia, South Korea and New Zealand.
There were nine new deaths in China on Tuesday, bringing the total there to 147.
And 202 new cases have been reported.
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