The disease in Sweet Tooth, known as “The Sick,” has largely wiped out humanity and society by the time that viewers are shot into its world. Beyond the dwindling number of actual humans, new hybrid people that are half-animal, half-human have emerged as well and are regarded by many as a problem. Individuals and organizations hunt them down and kill them because they see them as some sort of threat.
So, is “The Sick” real? Definitely not. There really isn’t any plausible scientific case for a virus of this size and power to actually take shape on our planet, but the face-value symptoms of the show’s H5G9 do mimic a lot of known viruses, specifically COVID-19.
Symptoms such as coughing, fever, and difficulty breathing definitely overlap with real-world viruses, but the notion that it would culminate in a world also inhabited by hybrid babies is purely a work of fiction.
Interestingly enough, when Sweet Tooth initially debuted as a comic book series back in 2009, the virus that destroyed humanity was known only as “The Sick.” This means that the creator and/or Netflix writers took some creative liberties in the television adaptation by naming the virus H5G9.
Whether or not this decision was made to align with recent real-world events and provide another layer of spookiness to the storyline has yet to be confirmed.
Source : https://www.distractify.com/p/sweet-tooth-virus-explained