Check out the lifecycle of the flea- it's amazing. They can stay dormant as eggs for up to 2 years and can live in the old carpet or gaps in the skirting board - which is most likely in your case.
Complain to landlord immediately - it is his responsibility. There are some very good sprays around from Vets but expensive for treating affected areas. If you don't treat it will get worse. Vacuumming every crack and crevice + spraying will help get rid.
I find that fleas are attracted to navy blue fabric like denim - anyone know why?
Freedom at the point of zero............