The Microbiome of Airborne Particles

Abstract

Airborne microorganisms can strongly influence environmental and human health. However, the airborne microbiome in many locations remains largely uncharacterized. Understanding what microbes are present, where they are located, and how they spread is essential for predicting their presence and function. The transport and spread of airborne microbes is affected by their associations with particles of different sizes. Associations with smaller particles also increases the likelihood that they will penetrate deeply into the lungs and bloodstream. In Chapter 1, I describe the airborne microbiome in the Sahara, a globally important source region for atmospheric dust. Results showed abundant and diverse microbes in all size fractions, including potential pathogens, even on fine particles (≤2.5 μm) that are capable of long-distance transport. In Chapter 2, I explored the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), in the air of a Boston hospital. I found airborne SARS-CoV-2 RNA to be present in all particle sizes tested and more prevalent in areas without COVID-19 patients. Presence of the virus on fine particles indicates the ability to remain airborne for extended periods of time and travel farther than six feet. In Chapter 3, I evaluated the location-dependent size distribution of airborne SARS-CoV-2. I conducted a study of SARS-CoV-2 in size-fractionated particles in a healthcare facility in Kuwait. Large particles (≥10 μm) were the predominant source of SARS-CoV-2 in symptomatic patient rooms. By contrast, outside the hospital entrance and in intubated patient rooms, viral RNA was more frequently associated with fine particles. These findings emphasize the importance of universal airborne precautions that protect against fine particles in all locations, including non-COVID-19 wards and outside the hospital. This research demonstrates airborne particles contain an abundant and diverse microbiome with important implications for human health and disease transmission.