No one knows how it started or who was responsible, what we do know is that the infection spread so quickly that no one even had time to find a cure. The "infection" was in truth a engineered retrovirus that altered the human genome that not only affected human development but also triggered a transformation in people who were experiencing puberty or older. Every one who was an adult or becoming sexually mature began to transform into monsters that had difficulty thinking about anything but sex.
The full affects of the changes to the human genome started from birth, all children are born looking female, and you'll stay younger for a little longer now experiencing puberty at around your early twenties. There are three stages that someone will go through wen they go into puberty. In the first stage you'll experience a sexual awakening feeling an urge to masturbate and having some perverted thoughts. The Second stage was wen your sexual organs begin to develop your clitoris will swell becoming a penis and your breasts grow in. This is also wen you'll typically start having sex.
The final stage is when the transformation begins and it will become difficult to think of anything other then sex, hunting for food, giving birth, and taking care of your babies. You won't be stupid though your brain is just over loaded with hormones. The transformation varies from person to person, typically you'll become very attractive, but usually will lose the human form in some way, and additional sexual organs often develop. Some other traits that have become common among humans are a wide variety of eye and hair colors, bioluminescence, and old age has become a thing of the past. People still die mind you but aging stops after your transformation and you'll typically live close to two hundred years or more, assuming you don't get yourself killed.
As you can imagine with the adults becoming horny monsters children had to take over running civilization. This doesn't work very well and civilization was forced to regress in some ways, things had to become a little more simple, and some technology was lost. But fortunately thanks to some very brilliant kids and occasionally and adult with strong self control some new self sustaining technologies have been created, which is good because the power grid shut down a few years ago.
So to summarize, babies and toddlers are cared for by their mother and siblings, wen your old enough you begin your education so that you can start participating in society as soon as possible. You will usually start with jobs like cleaning and helping in the gardens. As you get older you may choose to do something you love to do like cooking, knitting, taking care of the animals, and other things. The smartest of us will be the ones who make the big decisions, their the teachers and and the ones who maintain what technology we have left. But remember to not overwork yourself we're still kids so make sure to have fun wen you can.
Look I know how some of you feel we all eventually start to turn into a monster and that's scary. But remember we need to make sure that we keep things going so wen we have babies they can have good lives to. And don't forget to be nice to each other.