Test & Trace: what is a close contact?

[DecentPleasant]

Impossible to get a definitive answer it seems.
If person A tests positive on Friday and spent Wednesday in work with person B, when was A likely to be infectious? Symptoms started with headache on Friday. When is B ‘safe’?
Thank uou. I am B. I go nowhere apart from work and food shopping so feeling quite worried due to health issues.

Dp had close contact with someone on Wednesday who tested next day on lft and next day by pcr. Dp had a pcr test Friday evening which came back Saturday negative but a positive lft Sunday morning followed by pcr. He had symptoms but not any of the main 3 on Sunday. It can go from negative to positive really quickly!

They say you are contagious the 48 hours before symptoms start. If there's no symptoms and just a positive pcr, it's harder to pinpoint.

To add, Dp caught it off someone who was asymptomatic. His colleague only lft tested as his wife had covid. More people at there work has now tested positive over the weekend.

Close contacts are anyone they spent time with 48hrs before symptoms. So yes, you would be deemed a close contact if you were physically close to them on Wednesday.

Past 48 hours www.nhs.uk/conditions/coronavirus-covid-19/self-isolation-and-treatment/when-to-self-isolate-and-what-to-do/

More details here www.gov.uk/guidance/nhs-test-and-trace-how-it-works#how-nhs-test-and-trace-helps-fight-the-virus

Thanks for the replies and links and help. Very interesting and useful.