Up-to-date edition, all chapters and sections have been thoroughly updated with newer information. An entirely new part SARS COVID-19, under the section VIRAL INFECTIONS has been added, that cover major topics such as Covid-19: epidemiology, clinical course, treatment, lab-diagnosis, Covid complications and care clinics, etc. A separate chapter on Covid Vaccination is included. Section-HIV Medicine is broadened to various aspects including HIV Malignancy, Antiretroviral Therapy and interactions, HIV and Pregnancy, HIV-2 etc. A novel chapter on DNA-Repair Deficiency and Lysosomal Storage Disorders have been added. A separate chapter on the Impact of Covid-19 on Hospital Environment under section Environmental Medicine is presented separately., Authoritatively written by experts with immense knowledge and experience.