Airborne Transmission of COVID-19 in the Hospital

There has been a lot of talk about how COVID-19 is spread in the community and how it is spread within a hospital. The current understanding is that in the community, this disease is mostly spread through droplets (i.e. sneezing, coughing, or talking to infected people). One reason this virus may have spread so rapidly and broadly is through droplet transmission between asymptomatic individuals.

In the hospital, healthcare workers are wondering to what extent COVID-19 is an airborne illness, meaning how much of the virus is spread from small virus particles that linger in the air.

This is especially relevant nowadays when there is a massive shortage of personal protective equipment in the hospital as well as confusion about what type of equipment is needed in different settings. Currently, the CDC recommends using an N95 respiratory which filters 95% of airborne particles for protection in scenarios where disease transmission is airborne and a surgical mask when disease transmission is large droplet. Notably, this is different from the Chinese recommendations, which recommended N95 respirators for all inpatient hospital care during the Wuhan epidemic (Source: https://www.alibabacloud.com/universal-service/pdf_reader?spm=a3c0i.14138300.8102420620.dreadnow.6df3647fwVQwvF&pdf=Handbook_of_COVID_19_Prevention_en_Mobile.pdf).

CDC Infographic for N95 vs Surgical Mask
Source: https://www.cdc.gov/niosh/npptl/pdfs/UnderstandDifferenceInfographic-508.pdf

SARS-CoV-2 is Viable in Air for >3 Hours

van Doremalen et al. simulated aerosolization of SARS-CoV-2 virus with a nebulizer and a Goldberg drum apparatus and found that high viral loads remained in the air for more than three hours and that the stability of the virus was similar to the 2003 SARS virus. See: https://www.nejm.org/doi/full/10.1056/NEJMc2004973 for more details. This is significant because we can turn to the medical literature for what lessons we learned from the original SARS outbreak.

Source: van Doremalen et al. NEJM 2020

Lessons Learned from 2003 SARS Outbreak

The 2003 SARS virus was a respiratory disease that also emerged from China. Similar to our COVID-19 pandemic, the 2003 SARS disease also had an incubation time for about a week, was characterized by symptoms of fever, body aches, and cough, and had imaging findings of atypical pneumonia which could progress to ARDS.

The outbreaks of SARS were predominant in healthcare settings with large transmission to nurses, doctors, and hospital visitors. Many frontline healthcare professionals involved with aerosolized procedures contracted SARS and developed serious illness. For example, critical care nurses involved with intubation, suctioning, and nebulizer treatment had a four times increased risk of infection (Loeb et al. Emerging Infectious Diseases 2004. Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3322898/). SARS transmission was also associated with other procedures like noninvasive pressure ventilation and cardio-pulmonary resuscitation (Siegel et al. CDC 2007 Source: https://www.cdc.gov/infectioncontrol/pdf/guidelines/isolation-guidelines-H.pdf). The healthcare workers who contracted SARS the most were those who did not consistently use personal protective equipment (Gamage et al. Journal of Infection Control 2005. Source: https://www.ajicjournal.org/article/S0196-6553(04)00639-X/fulltext).

Tran et al. summarized all the aerosol generating procedures associated with increased SARS transmission (Tran et al. PLoS One 2012. Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3338532/). They found that tracheal intubation was the most consistent procedure associated with increased SARS. Statistically significant analysis of the other procedures was limited due to small sample size, but other procedures that had point estimates of increased transmission risk included suction before intubation, manipulation of oxygen masks, bronchoscopy, noninvasive ventilation, chest compressions, and collections of sputum samples.

Tran et al. Plos One 2012.

Summary

The big takeaways that I learned when reading about the 2003 SARS outbreak were that healthcare workers were the most at risk for infection, personal protective equipment and training are needed to decrease transmission of disease, and that extra precaution is needed during aerosol-generating procedures.

What we need now is more personal protective equipment. I agree with Andrew Cuomo’s call for the Federal Government to nationalize the medical supply chain. Without enough supplies, we are sending healthcare workers into a dangerous environment where they can get sick and die from illness.

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