Ok, I'm sick of reading all these nutjob 5G conspiracies. Let's get some real scaremongering on the go!
Toxoplasma. It's a parasite that infects mammals and can influence behaviour by remodelling their neurons. Typically, it infects rats and alters their neural pathways so that they're no longer afraid of cats - instead of the fear pathway being activated, the sexual pathway is now activated by the smell of cat urine.
This lack of fear is designed to make the rat more susceptible to being eaten by a cat, with felines being the only hosts that the parasite can fully reproduce within - before being crapped out again and eaten by more rats, completing the cycle.
Toxoplasma is one of the most common parasites in developed countries and it is estimated that up to 50% of the world's human population now has it. Recent studies have shown that it can indeed influence human behaviour too and infected humans are almost twice as likely to partake in risk-taking activities - one example being that hosts are statistically more likely to be entrepreneurs. Much like rats lose their fear of cats, humans seemingly lose their 'fear of failure'/inhibitions.
It's estimated that up to a third of UK residents have it and previous estimates show it to be much higher in some countries - e.g. 84% in France due to catching it from undercooked meat.
Now for the crazy theory part. I think it's hypothetically possible that a similar/mutated parasite could result in a global '28 Days Later' type pandemic. Especially considering that rabies (also a parasite) is transmitted by bites and hence makes the host ferally aggressive in order to bite and spread. It also makes them develop hydrophobia to prevent them drinking water and flushing the saliva/parasite from the mouth to the stomach where it can't be passed on (which is bad for the parasite which wants to spread).
A behaviour influencing parasite as contagious as toxoplasma but with similar properties to rabies could quite literally create a zombie outbreak where half the world's population become feral and want to bite people.
But maybe toxoplasma in it's current form is what's missing from my life! 😂