Widal test can be non specifically elevated even in COVID 19. Advice him to undertake a Covid 19 RT PCR test at earliest. And meanwhile keep him at home isolation. Give him nutritious, protein rich food, plenty of fluid orally. And you may use paracetamol for fever. And normal supplements like
vitamin c, zinc etc.
Next Steps
RTPCR test for Covid 19
Health Tips
please maintain home isolation for this patient while waiting for test results, and check spo2 at least 3-4 times if possible.