Washington (AFP) – President Joe Biden tested positive for Covid-19 on Thursday, with his doctors saying the 79-year-old leader was experiencing only mild fatigue and would isolate at the White House while carrying out his duties. Biden, who posted a picture of himself working at his desk, tweeted that he was “doing great” — and apologized for missing a scheduled event in Pennsylvania. He also released a short video clip filmed on a White House balcony, saying: “I really appreciate all your inquiries and concern, but I am doing well… it’s going to be OK.” Announcing Biden’s diagnosis, the W…