Why “la Covid-19” and not “le Covid-19”? After all, it’s a virus and the word virus is masculine in French (“un virus”). Don’t “le Covid-19” make sense?
For centuries, the “Académie de la Langue Française” in Paris, founded in 1634, was the only official authority on the usages, grammar, and vocabulary of the French language. Since then, French language has been spread here and there around the world, and other institutions have been founded such as the Translation Bureau at the Government of Canada, in 1934, and the Office Québécois de la Langue Française (OQLF) in 1961.
The gender chosen for “COVID-19” is a good example of the professionalism and notoriety that these two institutions gained over the years.
In May 2020, even though the masculine (“le Covid”) is paramount until then in France (in medias and conversations), l’Académie de la Langue Française, got along with the Translation Bureau and the OQLF, specifying - like both Canadian institutions did - that COVID is the acronym for "Corona Virus Disease". Disease being a feminine word in French (“la maladie”), then COVID-19 can no longer be masculine.