2. Fever
A fever is one of the earliest symptoms that most people develop int the case of an illness or infection. This means that your immune system is reacting to something it perceives as an attack and reacting to it, usually by increasing the body temperature in an attempt to rid the body of the pathogen or intruder.
Most people who contract Hantavirus will develop a fever first: This is true for most infections and illnesses out there to which the immune system reacts to.
A fever can be temporarily brought under control with the use of paracetamol, but will always need medical attention due to the primary underlying infection causing it. Careful with the rate at which fever and subsequent sweating might dehydrate the body: Intake of fluids is crucial.
Together with other symptoms on this list, it could mean that the fever is due to the Hantavirus: See a doctor for tests to establish this.