WASHINGTON (AP) – President Joe Biden has tested positive for COVID-19 on Thursday, making him the second U.S. president to get the virus and underscoring the extent to which the virus has infiltrated American society. The 79-year-old Biden is fully vaccinated after getting two initial doses of the coronavirus vaccine and two boosters since. When a fully vaccinated person experiences a breakthrough infection, the chance of severe illness or death is low. The announcement highlights the unpredictable nature of a virus that has now infected numerous world leaders, despite an urgent global vaccination drive and feverish efforts at containment.