Thread by @HaryaxPathak

Hey #MedTwitter

As promised, taking this thread further, I'll highlight a few more aspects about #COVID19.

A) TRANSMISSION and SPECIFIC PRECAUTIONS
B) WHAT IS SUPER-SPREADING?
C) WHAT IS R0?

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https://twitter.com/HaryaxPathak/status/1330803873980801025

A) TRANSMISSION and SPECIFIC PRECAUTIONS

So, what are the various mechanisms of COVID-19 transmission?

As defined by the @CDCgov, these are the 3 mechanisms of COVID-19 spread:

➡️Fomites (least important)
➡️Droplet Spread
➡️Aerosol

cdc.gov/coronavirus/20…

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➡️Fomites

Fomites are objects or materials which are likely to carry infection, such as clothes, utensils, and furniture.

They were thought to transmit COVID19 as well, but @CDCgov has said that COVID transmission through fomites is minimal.

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➡️Precautions for FOMITES

> Regular hand washing
> Cleaning/Disinfecting objects of frequent contact

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➡️Droplet Spread

"Droplet transmission is an infection spread through exposure to virus-containing respiratory droplets (i.e., larger and smaller droplets and particles) exhaled by an infectious person." - @CDCgov

Talking, coughing, sneezing, shouting produce droplets.

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Respiratory droplets can be of varying sizes - larger ones descend to the ground earlier; smaller ones can travel further - up to a distance of 6ft or 2m.

So, a healthy person within 6ft or 2m of an infected person can get infected by the droplets of the infected person.

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➡️Precautions for Droplets

> Personal Hygiene - cover the face while coughing/sneezing to prevent dispersion of droplets.
> Avoid Direct Contact
> Masks
> Social Distancing

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> Masks

Simply put, Masks reduce the dispersion of droplets to a great extent.

As shown in the image, Masks reduce the risk of contracting the infection if everyone masks up, irrespective of whether infected or healthy.

The next tweet explains WHY MASKS?

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Thermal plumes produced by a person.

In (a–c) no mask is worn, in (d–f) a non-surgical three-ply disposable mask is worn.

(a,d) sitting quietly breathing through their nose
(b,e) saying ‘also’ when speaking at a conversational volume
(c,f) laughing

bit.ly/3fyZFRk

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> Social Distancing

As mentioned above, droplets can travel up to 2 metres in the air.

That is precisely the reason for practicing Social Distancing - to keep yourself out of the range of droplet dispersion from a possibly infected person.

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➡️ AEROSOL TRANSMISSION

Infectious aerosols are suspensions of pathogens in particles in the air.

They can remain suspended in the air indefinitely; unless they are removed by air current or ventilation.

They can also travel nearly 10m distance.

bit.ly/363jk8P

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Droplet vs Aerosol

Droplets are larger in size and travel up to 2m.

Aerosols are far smaller in size (<5microns) and can travel further up to nearly 10m.

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This image clearly shows droplet and aerosols production and dispersion.

bit.ly/3l8plFn

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➡️Precautions for Aerosol Transmission

> Masks + Social Distancing - still most important and the primary mode of protection against infection.
> Reduce exposure time: Reduce time spent in proximity to other people as much as possible.
> Ventilation

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> Ventilation

A closed room with no ventilation allows accumulation and concentration of the aerosols which increases the risk of infection.

Adequate ventilation continuously recycles the air in a room and flushes out the aerosols, making them less concentrated.

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This here is an extremely helpful, interactive, and graphical representation of how Airborne Transmission works.

Must read and share.

english.elpais.com/society/2020-1…

by @javisalas

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B) WHAT IS SUPERSPREADING?

It is the disproportionate spread of infection from a single person to a large group of people - who then go on to infect more and more people - leading to an exponential rise in the number of infections.

GIF: vis.sciencemag.org/covid-clusters/

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➡️Super-spreader Events

Any event that leads to an outbreak of COVID, with a majority of the infections/cases tracing back to the said event can be called a Super-spreader event.

Such events cause large outbreaks and can be responsible for 100s to 1000s of cases.

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Super-spreader events can range from a small party or a family get-together to public gatherings like concerts, election rallies, religious gatherings, festivals like Diwali, Eid, Christmas, supermarkets, etc.

So, why does Super-spreading occur?

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C) WHAT IS R0?

A high R0 is the reason for super-spreading.

In simple terms, R0 is the average number of people infected by a single person.

R0 > 1 -->epidemic/pandemic
R0 = 1 -->stable/controlled spread
R0 < 1 -->minimal spread

COVID-19 has an estimated R0 b/w 2-6.

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Here is another extremely interesting and interactive article that explains how Super-spreader events occur and how R0 works in real life.

Must share.

vis.sciencemag.org/covid-clusters/

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➡️Prevent Super-spreading

>Avoid crowded places
>Avoid large indoor gatherings
>Ensure maximum natural indoor ventilation
>Avoid mass gatherings, especially during festivals

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To sum up:

➡️Transmission is mainly by droplets and aerosols.
➡️Masks, Distancing, Hygiene, and Ventilation are a must.
➡️To prevent Super-spreading events - avoid crowds and mass gatherings.

➡️Educate yourself and others. Share as much as possible.

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