Toddler severe tantrums, inconsolable fits

#advicepls my 2yr plus old son goes into 15mins-30mins severe meltdown every day for the past few days. He's having fever and flu for a while, so we thought it might be due to him feeling uncomfortable. But the meltdowns are quite bad. He would cry uncontrollably, scream, go hysterical and nothing can stop him. He throws himself backwards violently and sometimes starts hitting me when I tighten my grip on him (to prevent him from falling). Each meltdown goes on for more than 10mins, happens once or twice a day, and the trigger can be something really minor eg change diaper. Not sure if I aggravated or triggered though cos sometimes I'm just very loud and assertive. But he usually responds well to all these triggers. Just like to understand if this is normal behaviour, ie kid can go hysterical when sick for no reason. Or it's something we need to work on, eg it's a fundamental problem thats not due to sickness?.