Physics of breathing explains rapid secondary infections in the lungs

What is it about?

The study explores how microdroplets formed from mucosal liquids in the upper respiratory tract (URT) during inhalation may contribute to the rapid onset of deep lung infections following initial URT symptoms. Typically, particulates must be smaller than 5 micrometers to effectively reach the lungs. However, the fate of larger particulates, which can exceed this size and originate from the initially infected areas of the URT such as the nasopharynx, remains poorly understood. This research employed advanced imaging techniques to create a detailed 3D model of the airway. Within this model, the inhaled airflow and the movement of microdroplets ranging from 1 to 30 micrometers—fragmented from the mucosal substrate during inhalation—were simulated computationally. The high fidelity numerical findings (validated experimentally and theoretically) indicate that unexpectedly large microdroplets can penetrate the lower airways, carrying a significant viral load that may facilitate a quicker spread of lung infections. The results provide valuable insights on the mechanisms by which infections can rapidly progress from the upper to the lower respiratory tract.

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Photo by Aakash Dhage on Unsplash

Photo by Aakash Dhage on Unsplash

Why is it important?

The rapid onset of secondary lung infections cannot be solely attributed to the tissue-level replication of invading pathogens following the onset of the initial infection in the upper respiratory tract. This study is the first to conclusively demonstrate that downwind transmission to the lower airways could be explained by the physical mechanics of pathogen-rich mucosal fragments formed during inhalation near the sites of initial infection in the upper airway.

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