Dr. Fauci is not permitted to have a cat, because as director of the National Institute of Allergy and Infectious Diseases, his petting one would be considered giving aid and comfort to an allergen.
This comic is another in a series of comics related to the COVID-19 pandemic.
Jokes about professionals not being so professional in private have been presented before, for example in 2401: Conjunction and 1463: Altitude.
Dr. Anthony Fauci is the Director of the National Institute of Allergy and Infectious Diseases who was largely responsible for informing the public in the United States on how to avoid spreading SARS-CoV-2 in the beginning of the COVID-19 pandemic. He was recently awarded a one million dollar prize for his recent work. This may be the press conference he is going to. The comic shows him singing a silly made-up song to his pet fish as he goes about his daily routine - a counterintuitively childlike (albeit delightful and relatable) habit for an authority figure who normally presents himself to the public in a professional and prosaic "grown-up" manner. Incidentally, this characterization of Dr. Fauci doesn't seem to be far from the truth: Fauci's daughter Jenny is quoted in the Washington Post as saying of her father: "He's a goofball[...] He works hard and he does his thing, but he comes home and he's singing opera in the kitchen and dancing around."
In 231: Cat Proximity, it's presented as 'normal' for people to make inane statements and use baby talk near cats, but here, Dr. Fauci is singing to his fish. The title text explains that, as he is the director of the National Institute of Allergy and Infectious Diseases, he is forbidden from owning a pet cat, because petting the cat would be "giving aid and comfort" to an allergen, which is (a reference to) one definition of treason under the United States Constitution. The “allergen” refers to the hypothetical cat—some people are allergic to cats.