MEXICO CITY—Mexican President Andrés Manuel López Obrador said Sunday he has tested positive for COVID-19 and that the symptoms are mild. Mexico’s president said on his official Twitter account that he is under medical treatment. “I regret to inform you that I am infected with COVID-19,” he tweeted. “The symptoms are mild but I am already under medical treatment. As always, I am optimistic. We will all move forward.” His announcement came shortly after news emerged that he would speak with Russian President Vladimir Putin on Monday about obtaining doses of the Sputnik V COVID-19 vaccine. Mexico Foreign Affairs Secretary Marcelo Ebrard said via Twitter the two leaders would speak about the bilateral relationship and supplying doses of the vaccine. The vaccine has not been approved for use in Mexico but the government is desperate to fill supply gaps for the Pfizer vaccine. Mexico has given more than 618,000 vaccine …