Other causes could be SLE, rheumatoid arthritis, Polyarteritis nodosa (PAN) and other auto immune disorders, UTI, drug fever, sinusitis, glandular fever, otitis media, IBS, HIV, STDs, endocarditis, parasitic infestations (quite possible as you have a high eosinophil, hence get a stool test done), fungal infections, lymphomas
and other cancers etc.
Low grade fever is also seen in anemia, diabetes, hypothyroid states, overwork, stress and fatigue. Dehydration is another cause.