Opportunistic infections (OIs) are the growing concern as the microbe takes advantage when the immune system is weak. Even the microbes that reside in us for many years may cause serious disease when the immune system has weakened. Also, certain microbes get reactivated and cause opportunistic infections. Such common OIs include oral and pharyngeal candidiasis, Tuberculosis, Herpes Zoster, Bacterial pneumonia, Cryptoccal meningitis, Taxoplasmasis. Such secondary infections are common in immunocompromised and long term hospitalized severely ill patients. Currently, the incidence of secondary infections is increased world-wide in COVID-19 infected patients. The interface of biology, chemistry, computer science and mathematics has shown tremendous innovations in infectious diseases. In this book, such interdisciplinary approaches have been focused for the management of OIs. The edited book would be helpful for scientists, scholars, industrialist to obtain updated key information about interdisciplinary approaches to tackle opportunistic infections.