SEATTLE (AP) — Microsoft co-founder Bill Gates says he has tested positive for COVID-19 and is experiencing mild symptoms. Via Twitter, the billionaire philanthropist said Tuesday he will isolate until he is again healthy. Gates wrote that he’s fortunate to be vaccinated and boosted and have access to testing and great medical care. The Seattle-based Bill and Melinda Gates Foundation is the most influential private foundation in the world, with an endowment of about $65 billion. Bill Gates has been a vocal proponent for pandemic mitigation measures, specifically access to vaccines and medication for poorer countries. The Gates Foundation in October said it will spend $120 million to boost access to generic versions of drugmaker Merck’s antiviral COVID-19 pill for lower-income countries.