Mexico’s President Andrés Manuel López Obrador announced Sunday that he has tested positive for COVID-19.

“I regret to inform you that I am infected with COVID-19,” López Obrador tweeted. “The symptoms are mild but I am already under medical treatment. As always, I am optimistic. We will all move forward.”

López Obrador confirmed that he will continue working following the diagnosis, including taking a call with Russian President Vladimir Putin on Monday about obtaining doses of the Russian Sputnik V COVID-19 vaccine.