Functional assays are critical in the field of infectious diseases for several reasons: - They help in the identification and development of new antimicrobial agents. - They provide insights into the mechanism of action of drugs, which is crucial for understanding how these agents work. - They are used to assess the virulence of different pathogens, which aids in the development of vaccines and other preventive measures. - They can identify resistance mechanisms, helping to combat antimicrobial resistance.