The WHO Strikes Back: Droplet vs. Airborne Precautions

I cannot believe that there is still a mystery from the WHO as to whether COVID is a droplet or airborne virus. The World Health Organization has obtained the paper I referenced yesterday. In addition, the study in the NEJM that I covered on 3/18/2020. Please read the document for yourself. I have provided links, as always. Please interpret this data yourself. Don’t trust me.

Regarding the NEJM study which concluded that the virus could be in the air up to three hours:

Their take: “the finding of COVID-19 virus in aerosol particles up to 3 hours does not reflect a clinical setting in which aerosol-generating procedures are performed—that is, this was an experimentally induced aerosol generating procedure.”

My take: can you please give us some data as to how long we could expect it during clinical settings of aerosol-generating procedures to be in the room? Can we have some expert guidance?

Regarding the study I posted yesterday, 3/30.
The WHO provided citations for two studies, one published in JAMA (Ong study) and the other in Infection Control and Hospital Epidemiology to disprove the Santarpia study.

Their take: “It is important to note that the detection of RNA in environmental samples based on PCR-based assays is not indicative of viable virus that could be transmissible. Further studies are needed to determine whether it is possible to detect COVID-19 virus in air samples from patient rooms where no procedures or support treatments that generate aerosols are ongoing. As evidence emerges, it is important to know whether viable virus is found and what role it may play in transmission.”

My take: since we don’t know with reasonable certainty, then we should err on the side of caution and protect our teams.

Here are the two studies cited by WHO as to why it is NOT airborne but droplet.

Ong study: sampled 3 patients, the one who was the sickest noted the virus in the air outlet fans (airborne infection isolation rooms). Per the article, this suggests “that small virus-laden droplets may be displaced by airflows and deposited on equipment such as vents”. The limitation stated by the authors includes that “the volume of air sampled represents only a small fraction of total volume, and air exchanges in the room would have diluted the presence of SARS-CoV-2 in the air. Further studies are required to confirm these preliminary results.” In this study they also found the virus on the shoe of a physician.

My take: Hardly concrete not definitive.

Cheng study: “air samples were all undetectable for SARS-CoV-2 RNA when the patients were performing 4 different maneuvers (normal breathing, deep breathing, speaking 1, 2, and 3 continuously, and coughing continuously) while putting on and putting off the surgical mask.”

It seems based on the discussion that they did this on only ONE patient. They state “we may not be able to make a definite conclusion based on the analysis of a single patient”.

My take: inconclusive.

My understanding is that a viral culture is needed to assess viability rather than PCR. Neither of these studies looked at viral cultures. WHO, can you get this for us?

All in all, I believe that their attempts leave much to be desired as to whether COVID-19 should be treated as airborne or droplet by the WHO.

Click here for breakdowns of other COVID-19 Articles.


WHO Commentary on Transmission Modalities

Cheng V, Wong S-C, Chen J, Yip C, Chuang V, Tsang O, et al. Escalating infection control response to the rapidly evolving epidemiology of the Coronavirus disease 2019 (COVID-19) due to SARS-CoV-2 in Hong Kong. Infect Control Hosp Epidemiol. 2020 Mar 5 [Epub ahead of print].
Link to AbstractLink to FULL FREE PDF

Ong SW, Tan YK, Chia PY, Lee TH, Ng OT, Wong MS, et al. Air, surface environmental, and personal protective equipment contamination by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from a symptomatic patient. JAMA. 2020
Link to FULL FREE Article

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