RISK ANALYSIS FOR COVID AND EVIDENCE-BASED PREVENTION METHODS

Updated: Feb 6


Firstly, we need to understand our enemy, this very potent virus that has become difficult to contain, resulting in a pandemic affecting nearly  all the countries and bringing the world to almost a standstill.

OUR INVISIBLE ENEMY - COVID -19 VIRUS (1)


A novel strain of coronavirus — SARS-CoV-2 — was first detected in December 2019 in Wuhan, a city in China’s Hubei province with a population of 11 million, after an outbreak of pneumonia without an obvious cause. The virus has now spread to over 200 countries and territories across the globe and was characterised as a pandemic by the World Health Organization (WHO) on 11 March 2020. 


As of 17:00 on 24 June 2020, 43,230 of these have died from COVID - 19 in the UK, and 512 K plus in all of the world. 


SPREAD (2)


SARS-CoV-2 belongs to a family of single-stranded RNA viruses known as coronaviridae, a common type of virus which affects mammals, birds and reptiles. In humans, it commonly causes mild infections, similar to the common cold, and accounts for 10–30% of upper respiratory tract infections in adults. However, it is more than just a common cold and the incubation period of a coronavirus varies but is generally up to two weeks.


The preliminary reproduction number (i.e. the average number of cases a single case generates over the course of its infectious period) is currently estimated to be between 1.4 to 2.5, meaning that each infected individual could infect between 1.4 and 2.5 people.



MODE OF ATTACK (3,4)


Viruses are difficult to kill as it replicates inside a human cell as opposed to bacteria, so any medication to destroy the viral load must be protective of the human cell and that is why it is tricky. The virus does not kill the host cell but uses it to replicate and then mostly attacks the lung tissues.



SIZE AND REACH OF THE ENEMY


Coronavirus particles are spheres with diameters of approximately 0.125 microns (125 nm). The smallest particles are 0.06 microns, and the largest is 0.14 microns. When it is coughed out - the droplets which are bigger (50 - 100 microns)  usually travel about 1-2 meters and the aerosol (>5microns) can travel up to 6 meters.



Picture courtesy - @Zianaart


DANGERS OF THE VIRUS (6,7)


  • Infectious people are asymptomatic for up to 72 hours with some not showing any symptoms at all.

  • It can remain suspended in the air from an hour to 3 hours.

  • Aerosol can travel in air and settle anywhere remotely from the infectious person.

  • Virus can remain viable and infectious in aerosols for hours and on surfaces, up to days. An infectious virus could be detected on copper surfaces for up to 4 hours, on cardboard for up to 24 hours, and on plastic and stainless steel for at least 72 hours in one of the studies.


RISK ANALYSIS


There is always a risk if we go outside and less of a risk if we stay at home but we need to go out to buy essentials or for exercise, so we have to weigh the risks. (8)


There are 3 suggestions to decrease risk. All three have been shown to really improve the condition in the countries that have followed it. They are:

  1. Social distancing

  2. Hand washing 

  3. Wearing a mask

The first two measures have been adopted by most countries and the public seems to have accepted it but not everyone agrees on the topic of wearing masks with some people completely against this practice.



THEORIES AGAINST MASKS

Various authors have justified not wearing masks based on four main grounds:


  1. There is limited evidence that masks are effective from a well-structured study.

  2. They argue that trials have shown that people are unlikely to wear them properly or consistently, which is important since prevention depends on people not repeatedly touching their mask, and on all or most people wearing them most of the time. 

  3. They point out that wearing a mask might make people feel safe and hence disregard other important public health advice such as hand washing and social distancing.

  4. They argue that because of the shortage of masks in the current crisis, the public should not wear them since healthcare workers need them more, and public buying could lead to major supply chain problems.


Personally, I am a great supporter of wearing masks.


COUNTRIES AND STATISTICS


Another significant theory is comparing the dates when countries began using masks and the total number of people affected by COVID in those countries. Have a look at this table below of the first few countries that adopted it (9):


Some countries were mask-wearing countries, to begin with, and the numbers shown from there are also quite remarkable. These were some of the first exposed countries but they contained the virus quite well and I do think that the masks have had a huge role. Please check this video showing how the patient numbers increased from the beginning and how countries came up on the list and moved up the table. (https://www.youtube.com/watch?v=DWVNml5HCPc ) (10)

So these numbers compared to the thousands that died in the non-mask wearing countries should ring an alarm.


One other article that caught my eye is about a letter to the editor regarding a man on the bus, a typical case of cluster outbreak caused by public transportation exposure. He first travelled from the city to the county, the bus journey being 2.10 hours and 39 passengers on board, he was having a cough so when he reached the first interchange, he bought himself a mask and continued his journey to his village in another bus with 14 passengers and a duration of 50 minutes. When this man was diagnosed as COVID positive, the remaining passengers were investigated and it came to light that 5 passengers from the first ride were infected, whereas none from the second ride where he wore a mask got infected. (11)


Another incident that helped increase my confidence in wearing masks is when 45 people of a 60-member choir were infected from one person, over a 2.5 hr period of practice and 2 of them succumbed to COVID 19 in Los Angeles. Singing, talking, coughing all produces droplets and aerosols. Droplets of 100 microns can travel for up to 1 meter and droplets of 50 microns as far as 2 meters. So the only way you can prevent inhaling it or getting it into your system is covering your nose, mouth and eyes from the droplets, which is usually quite efficiently done by any form of protection over them. (12)



COVID AND MATHEMATICS!


1. Mathematicians have been pointing out since January the predicted 4.9% chance of transmission in early January if EVERYONE wore masks (13) . It is estimated that approx 25% could be asymptomatic or pre-symptomatic at any one time in the population. Numbers are significant even if only 20% of people wore a mask as this would reduce the rate by - 


20% x 25% x 98.5% = 4.9% reduction


100% x 25% x 98.5% = 24.6%



2. I also came across these calculations according to which, if you were wearing any mask your chance of transmission, assuming someone was within 2 meters and infected with no mask, would only give a 30% reduction in the chance of transmission (i.e. 100% -70%).

If there was more than one infected person, the chance of transmission would be cumulative - i.e 

1 person = 70%

2 people = 91%

3 people = 97.3%

4 people = 98.6%....etc

i.e. 4 or more not wearing a mask within 2 meters would make no significant difference to your chances. These figures assume that the chance of infection with no protection within 2 meters of the infected is 100%, which is unlikely to be the case.



3. Another calculation I came across is (assuming the chance is 1 if no masks are worn.)


If you wear a mask and the other person doesn't and is infected = 70% chance of transmission 

Conversely, if the wearer is infected = 3% Chance of transmission

BOTH with masks, one infected = 1.5% chance of transmission


The benefits are likely to be greatest when face masks are used in conjunction with other practices (such as social-distancing and handwashing ), and when adoption is nearly universal and compliance is high. Hence, in my opinion, everyone should wear masks. Do it to protect others and it will help overall. The more it catches on, the more people we protect and the more we will be protected by  a magnitude - exponentially so! Literally a 'snowball effect'.


SO LET US ALL WORK TOWARDS SNOWBALLING THIS POSITIVE EFFECT- A SMALL BUT A SIGNIFICANT CONTRIBUTION!


P.S : I have listed a few more pieces of evidence from more recent publications at the end of the evidence for your own research and conclusions.


REFERENCES


1. WHO link of world stats for COVID -19 - https://www.gov.uk/guidance/coronavirus-covid-19-information-for-the-public


https://www.worldometers.info/coronavirus


2. COVID-19 is not a common cold - https://jamanetwork.com/journals/jama/fullarticle/2759815


This video - explains what happens when you get COVID -19 and ARDS

https://www.youtube.com/watch?v=OOJqHPfG7pA



3. The best video I have seen so far explaining how the virus caused COVID-19 - https://www.youtube.com/watch?v=5DGwOJXSxqg


4. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-(https://www.nejm.org/doi/10.1056/NEJMc2004973)


5. The diamond princess cruise ship, 3711 people on board. When tested 634 people were found to be positive, of which 328 (more than 50%) showed no symptoms.


https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2020.25.10.2000180#html_fulltext



6. Universal screening was done for women admitted for delivery at a maternity ward in a hospital in NewYork for COVID-19. In 1 month 215 people tested, 33 were shown to be positive, and of them, only 4 showed any symptoms. 


https://www.nejm.org/doi/full/10.1056/NEJMc2009316


7. Risk analysis of staying in v/s going out 


https://www.youtube.com/watch?v=n6QwnzbRUyA


8. The first 50 countries adopting wearing masks

https://www.aljazeera.com/news/2020/04/countries-wearing-face-masks-compulsory-200423094510867.html


https://www.newshub.co.nz/home/world/2020/04/coronavirus-countries-where-face-masks-are-mandatory-in-covid-19-fight.html


9. The video of the top 20 countries that got the virus from Jan - May 2020 - https://www.youtube.com/watch?v=DWVNml5HCPc


10. Man on the bus in China

https://onlinelibrary.wiley.com/doi/full/10.1111/irv.12740


11. The news of the choir members getting infected with COVID -19

https://josiebrown.com/wp-content/uploads/2020/04/


12. Mathematician calculation about adopting mask-wearing


https://www.sciencedirect.com/science/article/pii/S2468042720300117



SOME MORE EVIDENCES FOR WEARING MASKS


https://www.cam.ac.uk/research/news/everyone-should-wear-masks-in-covid-19-crisis-say-cambridge-researchers


https://www.sciencedaily.com/releases/2020/06/200612172200.htm


https://royalsocietypublishing.org/doi/full/10.1098/rspa.2020.0376#d1e2177


https://medicalxpress.com/news/2020-05-covid-transmission.html


Systematic review and meta-analysis 

https://www.sciencedirect.com/science/article/pii/S0140673620311429


https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818


https://www.thelancet.com/pdfs/journals/lanres/PIIS2213-2600(20)30134-X.pdf


Systematic review for flu virus and masks 

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/64D368496EBDE0AFCC6639CCC9D8BC05/S0950268809991658a.pdf/face_masks_to_prevent_transmission_of_influenza_virus_a_systematic_review.pdf


Informative videos by WHO https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public/when-and-how-to-use-masks