Airborne Transmission of SARS-CoV-2: What We Know academic.oup.com/cid/advance-ar… Paper from our @theNASEM #EnviroHealthMatters workshop. Source-to-dose framework, like for particulate matter and health effects, and 4 critical questions: /1
Q1: What size particles are generated by people & how do they spread in air? A: Large range of sizes and concentrations, aerosols+droplets important at short range (<1.5 m), aerosols dominate exposure at longer range (>1.5 m). /2
Q2: Which size particles are infectious and for how long? A: <5 μm and probably larger, half-life is around 1 hr /3
Q3: What behavioral and environmental factors determine personal exposure to virus? A: masks, ventilation (this focused on engineering...obviously choices about going out and socializing matter, too) /4
Q4: What do we know about the infectious dose and disease relationship? A: Depends on host & environmental factors, dose-response relationship not yet known nor how it and individual characteristics affect severity of disease /5

• • •

Missing some Tweet in this thread? You can try to force a refresh
 

Keep Current with Linsey Marr

Linsey Marr Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!

PDF

Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @linseymarr

13 Jan
Our multidisciplinary team sought to correct some bits of conventional wisdom on transmission of viruses through the air. Still working with historian @ethomasewing and others to show how these bits became embedded. journalofhospitalinfection.com/article/S0195-… Myths... /1
Myth 1: “Aerosols are droplets with a diameter of 5 μm or less”

Myth 2: “All particles larger than 5 μm fall within 1-2 m of the source”

Myth 3: “If it's short range [close contact], then it can't be airborne”

/2
Myth 4: “If the basic reproductive number, R0, isn't as large as for measles, then it can't be airborne”

Myth 5a. “If it's airborne then surgical masks (or cloth face coverings) won’t work”

Myth 5b: “The virus is only 100 nm (0.1 μm) in size so filters and masks won't work”

/3
Read 4 tweets
27 Dec 20
A 🧵on humidity and airborne viruses. Several articles have said that at higher relative humidity (RH), droplets/aerosols retain more water, are larger, and then fall out of the air faster. True, but the effect of RH on biological decay is probably more important. /1
.@DrWanYang and I studied this question in 2011, exploring different removal mechanisms from air as a function of RH. I thought we’d find that at high RH, droplets/aerosols would be a lot larger and settle out quickly. journals.plos.org/plosone/articl… /2
But the biological inactivation rate is more sensitive to humidity. See bigger steps in RH for inactivation than for settling in Fig. 5. We used decay rates for influenza from Harper 1961. Also note the difference ventilation makes at 1 vs. 10 ACH. /3
Read 13 tweets
14 Dec 20
Absolute 🔥 from the inimitable @edyong209! So much insight, so succinctly written, with input from scientists with deep expertise (from well before 2020) on viruses. Excerpts with my thoughts follow... /1
Their movements through the air have been poorly studied, too. “There’s this very entrenched idea,” says Linsey Marr at Virginia Tech, that viruses mostly spread through droplets (short-range globs of snot and spit)... /2
rather than aerosols (smaller, dustlike flecks that travel farther). That idea dates back to the 1930s, when scientists were upending outdated notions that disease was caused by “bad air,” or miasma. /3
Read 8 tweets
23 Nov 20
We started studying cloth masks in March. Preprint now at medrxiv.org/content/10.110… Take-home: Cloth masks are not an N95, but they work reasonably well for aerosols 1-2 microns and larger, which is the size that we think mostly mediates transmission. See thread. /1
.@jinpan @charbeleharb & Leng tested vacuum bag, microfiber, coffee filter, MERV 12 filter, cotton, acrylic, bandana, CDC sewn & non-sewn designs, surgical mask, face shield for material filtration efficiency in a filter holder and inward and outward protection on a manikin /2
For submicron particles, vacuum bag, microfiber, and surgical mask filtered out >50% of aerosols. Other materials were way below 50%. /3
Read 6 tweets
5 Oct 20
CDC's new guidance is out: "COVID-19 can sometimes be spread by airborne transmission" cdc.gov/coronavirus/20… /1
"Some infections can be spread by exposure to virus in small droplets and particles that can linger in the air for minutes to hours. These viruses may be able to infect people who are further than 6 feet away from the person who is infected or after that person has left...." /2
"This kind of spread is referred to as airborne transmission and is an important way that infections like tuberculosis, measles, and chicken pox are spread." /3
Read 7 tweets
25 Jul 20
Nearly tears of joy seeing new paper in medical journal with correct analysis and interpretation of aerosol transmission: thelancet.com/journals/lanre… See thread for summary of main points. /1
Where we have been: "Current infection control policies are based on the premise that most respiratory infections are transmitted by large respiratory droplets—ie, larger than 5 μm— produced by coughing and sneezing, then deposited
onto exposed fomite or mucosal surfaces." /2
Pathogens (e.g., M. tuberculosis, influenza, RSV, rhinovirus, many more) are consistently found in small aerosols <5 microns and if size-resolved data available, in much higher amounts than you would expect based on aerosol or droplet volume. /2
Read 11 tweets

Did Thread Reader help you today?

Support us! We are indie developers!


This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!