In the USA you only are 'suggested' to quarantine for 5 days after the date of exposure. Aside from that, if you get a positive test...immediately get yourself another one. I was there in January and my DD got a positive when I got a negative and I was 95% sure she was also negative. There's a story but the short version... based on the testing we had done in the previous few days and what precautions we took I was pretty sure it was a false negative. I was right...got her a real NP swab and it was negative.