People infected with HIV may just feel like they have a cold or flu.
For some people, HIV presents no, or very mild, symptoms. The latent phase of HIV can last for 10-15 years in some people, and while the individual may stay symptom free, they can pass on the infection.
You can test easily at home; all it takes is a finger prick.
More information can be found at https://www.nhs.uk/conditions/hiv-and-aids/