Source control (respiratory disease)

Source control is a strategy for reducing disease transmission by blocking respiratory secretions produced through breathing, speaking, coughing, sneezing or singing.

[2] In the past, suggestions have been made that covering the mouth and nose, like with an elbow, tissue, or hand, would be a viable measure towards reducing the transmissions of airborne diseases.

[6] In 2013, Gustavo et al. looked into the effectiveness of various methods of source control, including via the arm, via a tissue, via bare hands, and via a surgical mask.

[11] Cloth face masks can be used for source control (as a last resort) but are not considered personal protective equipment[12][11] as they have low filter efficiency (generally varying between 2–60%), although they are easy to obtain and reusable after washing.

[23][24] Despite the aforementioned belief, a 2020 research by the NIOSH and CDC shows that an uncovered exhalation valve already provides source control on a level similar to, or even better than, surgical masks.

[10] HIV was a noted co-infection in around 35% of those affected by TB in some regions of the US,[31] despite extended close contact being a requisite factor for infection.

[30] In 2007, the CDC HICPAC published a set of guidelines, called the 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings, suggesting that use of "barrier precautions", defined as "masks, gowns, [and] gloves", would not be required, so long as it was limited to "routine entry", patients were not confirmed to be infected, and no aerosol-generating procedures were being done.

"Standard precautions" requiring the use of masks, face shields, and/or eye protection, would be needed if there was potential for the spraying of bodily fluids, like during intubation.

[36][37] During the COVID-19 pandemic, cloth face masks for source control had been recommended by the U.S. Centers for Disease Control and Prevention (CDC) for members of the public who left their homes, and health care facilities were recommended to consider requiring face masks for all people who enter a facility.

[38] Masking patients reduces the personal protective equipment recommended by CDC for health care personnel under crisis shortage conditions.

Use of masks for source control is still recommended in times of high viral activity, but the CDC did not provide numbers for benchmarks.

The new policies are thought, according to the New York Times, based on various citations to medical literature, to increase mortality among vulnerable patients, especially those with cancer.

The 2023 paper also cites a research letter published in 2022, that suggests that the surge of COVID-19 cases in hospitals may have been due to the high contagiousness of Omicron,[42] an article which suggested a high secondary attack rate relative to Delta,[43] and papers finding increased mortality of cancer patients due to higher rates of breakthrough infections.