Why is 'a fever' correct rather than 'fever'?

I have a fever” is a set phrase .Set phrases are exceptions than the normal rules . These exceptions are to be used as directed. No question of why and how. If you too grammarian you have another answer: “ I have fever. read more

The child has a fever or the child has fever. Both are correct. Other examples : It’s nothing but a fever dream," she cried. She was fighting a fever, one that made it hard for her to focus. The strange fever remained, making her feel as if she'd been sitting in a sauna for hours. read more

Fever is usually associated with physical discomfort, and most people feel better when a fever is treated. But depending on your age, physical condition, and the underlying cause of your fever, you may or may not require medical treatment for the fever alone. read more