The new coronavirus struck at the heart of Mexican President Andres Manuel Lopez Obrador's inner circle on Thursday as Finance Minister Arturo Herrera said he was infected.
Herrera, the most high-profile member of the cabinet to test positive for the virus, said he only had "minor" symptoms.
"From this moment I will be in quarantine, and continue working from my house," he said on Twitter.
One of Lopez Obrador's closest advisors, Herrera was seen in a video standing next to his boss on Monday at the National Palace in central Mexico City where both have their offices.
A photo from a week ago showed them standing close to each other and talking outside. Neither was wearing a mask to cover the mouth and nose as recommended by public health experts to limit the spread of the virus.
The president's office did not immediately respond to a request for comment.
The virus has hammered Mexico's economy and brought life to a standstill for many months. Still, the peso and stock exchange largely shrugged off the news, with one trader saying it was because Herrera's symptoms were reportedly mild.
It is not clear if Herrera's positive diagnosis will impact Lopez Obrador's planned trip to Washington next month to meet US President Donald Trump.
Earlier this month, Lopez Obrador shrugged off calls to take a coronavirus test when another member of his inner circle also tested positive.
Mexico has darted up the list of countries hardest-hit by coronavirus and now has the seventh-highest death toll globally.
Lopez Obrador has been criticized by some Mexicans for his handling of the pandemic, including accusations that he did not take the virus seriously enough at the start and sent the wrong signal by not wearing a mask in public.
Last week Herrera accompanied the president on his visit to the central Mexican state of Hidalgo.