Can you explain "dirty Asian" in American stereo type?

I heard people saying Asians are dirty. And, it's among the stereotypes. but I mean.. in what way? we have dirty restaurants or our ways of doing things are dirty or house is dirty or personality is dirty? I mean.. Chinese government is dirty they are hiding and do bad things behind and lots of Japanese yakuza is dirty definitely. Is that what you mean?

Can you explain "dirty Asian" in American stereo type?
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