RESUMO
INTRODUCTION: In health care, measures against cross-transmission of microorganisms are codified by standard precautions, and if necessary, they are supplemented by additional precautions. STATE OF THE ART: Several factors impact transmission of microorganisms via the respiratory route: size and quantity of the emitted particles, environmental conditions, nature and pathogenicity of the microorganisms, and degree of host receptivity. While some microorganisms necessitate additional airborne or droplet precautions, others do not. PROSPECTS: For most microorganisms, transmission patterns are well-understood and transmission-based precautions are well-established. For others, measures to prevent cross-transmission in healthcare facilities remain under discussion. CONCLUSIONS: Standard precautions are essential to the prevention of microorganism transmission. Understanding of the modalities of microorganism transmission is essential to implementation of additional transmission-based precautions, particularly in view of opting for appropriate respiratory protection.