Thread by @NicholasChiuMD

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⭐️Respiratory virus shedding in exhaled breath & EFFICACY OF FACE MASKS?

This #Tweetorial, @BUMedicine classmates/future @BIDMC_IM coresidents @RahulAggarwalMD and I review:

🔷@NatureMedicine (hot-off-press 🔥04/03)
@bencowling88

#MedTwitter #MedEd #COVID19 @MedTweetorials

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First off: a question to test understanding of the size difference between RESPIRATORY DROPLETS and FINE-PARTICLE AEROSOLS:

What is the diameter cutoff for a droplet to be considered a FINE-PARTICLE AEROSOL?

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5 micrometers is the traditional cutoff for defining FINE-PARTICLE AEROSOLS.

So, when public health officials refer to a virus as airborne, they mean transported in virus-laden aerosols smaller than 5 micrometres in diameter.

Back to the objective of this study…

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BACKGROUND:
Viruses spread b/w humans through director/indirect contact, RESPIRATORY DROPLETS & FINE-PARTICLE AEROSOLS. Little is known about efficacy of masks in filtering infectious respiratory virus droplets.

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KEY CLINICAL QUESTION OF STUDY:

🔷Quantify AMOUNT of respiratory virus in EXHALED BREATH of pts w/ respiratory viral illnesses

🔷Determine the EFFICACY of SURGICAL FACE MASKS in preventing transmission of human coronaviruses and influenza from symptomatic individuals.

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POPULATION

-3363 individuals screened in two study phases

-Enrolled 246 pts who PROVIDED EXHALED BREATH SAMPLES

SAMPLE COLLECTION METHOD:

Bioaerosol collecting device: captures exhaled breath particles and differentiates into RESPIRATORY DROPLET (>5 µm) & AEROSOL (≤5 µm)

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INTERVENTION

246 pts 1:1 RANDOMIZED TO:

🔷NOT WEAR FACE MASK during 1st exhaled breath collection (122 pts)

🔷WEAR FACE MASK during 1st exhaled breath collection (124 pts)

49 pts (20%) voluntarily provided a 2nd exhaled breath (of ALTERNATE TYPE than 1st)

See graphic..

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RECALL goal: see if masks prevent transmission from SYMPTOMATIC pts…so, ≥1 virus had to be confirmed by PCR:

≥1 virus (n=123)
Corona (n=17)
Influenza (n=43)
Rhinovirus (n=54)
Corona/Influenza co-infect (1)
Rhino/Influenza co-infect (2)

⭐️111 TOTAL pts as FOCUS OF ANALYSIS

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OUTCOME MEASURES

VIRAL SHEDDING in terms of viral copies per sample (TOTAL VIRUS by PCR) in:

🔷Nasal swabs
🔷Throat swabs
⭐️Respiratory droplet samples
⭐️Aerosol samples

For the two ⭐️ samples, VIRAL SHEDDING was compared between samples collected WITH vs. W/OUT FACE MASK

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RESULTS (NASAL VS. THROAT)

🔷Nasal swabs
🔷Throat swabs

Viral shedding HIGHER in NASAL SWABS than in throat swabs for:

-Coronavirus (8.1 log10 virus copies per sample vs. 3.9)
-Influenza (6.7 vs. 4.0)
-Rhinovirus (6.8 vs. 3.3)

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VIRAL RNA identified from both RESPIRATORY AND VIRAL DROPLETS for all 3 viruses while NOT WEARING A FACE MASK:

⭐️RESPIRATORY DROPLETS:
Coronavirus: 30%
Influenza: 26%
Rhinovirus: 28%

⭐️AEROSOL:
Coronavirus: 40%
Influenza: 35%
Rhinovirus: 56%

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Detection of virus WHEN WEARING MASKS vs NOT:

⭐️RESPIRATORY DROPS:

-Coronavirus: Reduction (p=0.09, not quite 0.05 level) to 0 of 11 (0%) from 3 of 10 (30%) (p=0.09)

-Influenza: Significant reduction ⬇️ to 1 of 27 (4%) from 6 of 23 (26%) (p=0.04)

-Rhinovirus: Not sig.

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Detection of virus WHEN WEARING MASKS vs NOT:

⭐️AEROSOL:

-Coronavirus: Significant reduction ⬇️ to 0 of 11 (0%) from 4 of 10 (40%) (p=0.04)

-Influenza: Not significant

-Rhinovirus: Not significant

(*Viral Load results in bottom half of image)

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DISCUSSION/CONCLUSIONS:

"AEROSOL TRANSMISSION is a potential mode of transmission for CORONAVIRUSES as well as influenza and rhinoviruses."

"SURGICAL FACE MASKS could prevent transmission of human CORONAVIRUSES and INFLUENZA viruses from SYMPTOMATIC individuals."

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DISCUSSION/CONCLUSIONS CONT'D:

"This has important implications for control of COVID-19, suggesting that surgical face masks could be used by ILL PEOPLE to REDUCE ONWARD TRANSMISSION."

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LIMITATIONS:

-Large proportion of pts w; undetectable viral shedding exhaled breaths (obtained in 30 min sampling durations)
-Study does not confirm infectivity of coronavirus or rhinovirus from exhaled breath

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Congrats to authors!
Nancy H. L. Leung et al.
 
#MedTwitter Q:
What are clinicians' thoughts on the study's implications for the use of masks in the clinical setting & considerations for the public? @bencowling88

#COVID19 #SARSCoV2 @CPSolvers @thecurbsiders @MedTweetorials