SUA Seagull
Well-known member
I apologise in advance for the length of this post, which I wrote for a local residents’ community forum where my son lives (in London). He, and a few NSC friends (one of whom is medically highly vulnerable) with whom I have shared the article by email, have encouraged me to post it on NSC, in an attempt to highlight the maths behind social distancing (“SD”). It's a personal analysis and serves simply to highlight the exponential maths and how spread can occur so rapidly.
I keep witnessing examples of people unashamedly and irresponsibly ignoring the government’s SD advice, as they’re either too selfish, ignorant or arrogant (or all of those things) to comprehend the effects of what they are doing. So, I would like to take the opportunity to try and assess the consequences of their selfish deeds. I have hence calculated how the virus spreads based on different SD/isolation scenarios, which are summarised in the table below.
Scenario A shows that the current viral spread rate (“R”) is estimated to be about 2.5 every 5 days, i.e. with no SD 1 person would infect 2.5 others by day 5. Those 2.5 others would each infect 2.5 others themselves by day 10, and so on, with the spread rising exponentially every 5 days. In this scenario, after 30 days 406 people would be infected from just 1 person at day 0.
At the currently (early stage, to be refined with further data) estimated UK mortality rate of 0.9% (per Imperial College study dated 16th March) then 1 selfish person would cause circa 4 deaths (i.e. 0.9% of 406) within 30 days, most likely among the elderly and vulnerable. That’s 4 dead people (almost certainly strangers to the virus-spreader) because - in direct contravention to the government’s advice - they decided to exercise in an open-air/close contact communal space, attend an intimate family gathering, have a few drinks with a group of pals, ignore the 2m separation rule. Think about that. They will kill 4 people by having spread the virus. All of which could have been avoided, all because they (apparently) knew better than the scientific and medical advice being offered and because "this is just a heavy flu" which, staggeringly, I am still hearing some people suggest.
High spread rates are now happening and infection rates will rise (we just won't know the consequences for a few days yet). The NHS will eventually become totally overwhelmed and, denied appropriate treatment, thousands of people will die. And not just from Covid-19; accident victims will not be treated as NHS and emergency services’ resources are focused on battling the virus.
Scenario B looks at what happens if 25% of people are isolated. Here, the spread rate, R, falls by 25% to 1.88. In this scenario, total infections from 1 person at day 0 would be 92, or only 23% of the "free for all" scenario A. This illustrates the exponential nature of the virus - an isolation rate of only 25% for a month would result in a 77% (i.e. 100%-23%) reduction in the infection rate. That's still far too high in terms of NHS capacity.
Scenario C looks at what happens If 50% of people are isolated, Here, R would fall by 50% to 1.25. In this scenario, total infections from 1 person at day 0 would be 15, or only 4% of the "free for all" scenario A. An improvement, but still not enough, when one considers that the above table is the spread rate for just one person.
The only way to eradicate the virus is to drive R below 1, so as to limit each person's spread rate R to less than one other person, so that eventually the virus dies out. Until a vaccine is developed we have to rely on aggressive SD/isolation, and so if the public can't be trusted to comply then, IMHO, lockdown must be imposed.
To achieve R<1 in the above illustration would require an isolation rate of about 61% or higher (scenario D, where R = 0.98). Total infections would be only 6 people, or 2% of the "free for all" scenario A. In other words, 61% SD/isolation would result in a 98% reduction in infections in one month. This will enable the NHS to cope far better. It will also allow 39% of people (key workers, medical professionals, emergency services, food suppliers, delivery men) to keep the country going to look after the rest of us until testing, identification, quarantine, vaccination and other strategies can be developed eventually to drive down R to zero.
In terms of age distribution Covid-19 attacks the oldest and most medically vulnerable members of society far more aggressively than it does the younger members. In terms of projected effects by age, see Imperial College estimated table below, to which I have added a third column to show you the estimated death rate in each age group of those who contract the virus.
So, if a someone gets infected and then visits their (or anyone else’s) grandma or grandpa, aged 80+, who themselves become infected, then the grandparent (based on current estimates) is expected to stand a 1 in 11 chance of dying.
This is deadly serious, literally. If everyone follows the SD/isolation rules then many, many lives will be saved and unnecessary tragedy avoided.
I end with a quote from Professor Michael Osterholm, an internationally recognised expert in infectious disease epidemiology. In a recent online interview alerting all to the risks of Covid-19 he said “I don’t want to scare everyone out of their wits, I want to scare them into their wits.” Poignant, and potentially life-saving, advice.
Please be safe everyone.
I keep witnessing examples of people unashamedly and irresponsibly ignoring the government’s SD advice, as they’re either too selfish, ignorant or arrogant (or all of those things) to comprehend the effects of what they are doing. So, I would like to take the opportunity to try and assess the consequences of their selfish deeds. I have hence calculated how the virus spreads based on different SD/isolation scenarios, which are summarised in the table below.
Scenario A shows that the current viral spread rate (“R”) is estimated to be about 2.5 every 5 days, i.e. with no SD 1 person would infect 2.5 others by day 5. Those 2.5 others would each infect 2.5 others themselves by day 10, and so on, with the spread rising exponentially every 5 days. In this scenario, after 30 days 406 people would be infected from just 1 person at day 0.
At the currently (early stage, to be refined with further data) estimated UK mortality rate of 0.9% (per Imperial College study dated 16th March) then 1 selfish person would cause circa 4 deaths (i.e. 0.9% of 406) within 30 days, most likely among the elderly and vulnerable. That’s 4 dead people (almost certainly strangers to the virus-spreader) because - in direct contravention to the government’s advice - they decided to exercise in an open-air/close contact communal space, attend an intimate family gathering, have a few drinks with a group of pals, ignore the 2m separation rule. Think about that. They will kill 4 people by having spread the virus. All of which could have been avoided, all because they (apparently) knew better than the scientific and medical advice being offered and because "this is just a heavy flu" which, staggeringly, I am still hearing some people suggest.
High spread rates are now happening and infection rates will rise (we just won't know the consequences for a few days yet). The NHS will eventually become totally overwhelmed and, denied appropriate treatment, thousands of people will die. And not just from Covid-19; accident victims will not be treated as NHS and emergency services’ resources are focused on battling the virus.
Scenario B looks at what happens if 25% of people are isolated. Here, the spread rate, R, falls by 25% to 1.88. In this scenario, total infections from 1 person at day 0 would be 92, or only 23% of the "free for all" scenario A. This illustrates the exponential nature of the virus - an isolation rate of only 25% for a month would result in a 77% (i.e. 100%-23%) reduction in the infection rate. That's still far too high in terms of NHS capacity.
Scenario C looks at what happens If 50% of people are isolated, Here, R would fall by 50% to 1.25. In this scenario, total infections from 1 person at day 0 would be 15, or only 4% of the "free for all" scenario A. An improvement, but still not enough, when one considers that the above table is the spread rate for just one person.
The only way to eradicate the virus is to drive R below 1, so as to limit each person's spread rate R to less than one other person, so that eventually the virus dies out. Until a vaccine is developed we have to rely on aggressive SD/isolation, and so if the public can't be trusted to comply then, IMHO, lockdown must be imposed.
To achieve R<1 in the above illustration would require an isolation rate of about 61% or higher (scenario D, where R = 0.98). Total infections would be only 6 people, or 2% of the "free for all" scenario A. In other words, 61% SD/isolation would result in a 98% reduction in infections in one month. This will enable the NHS to cope far better. It will also allow 39% of people (key workers, medical professionals, emergency services, food suppliers, delivery men) to keep the country going to look after the rest of us until testing, identification, quarantine, vaccination and other strategies can be developed eventually to drive down R to zero.
In terms of age distribution Covid-19 attacks the oldest and most medically vulnerable members of society far more aggressively than it does the younger members. In terms of projected effects by age, see Imperial College estimated table below, to which I have added a third column to show you the estimated death rate in each age group of those who contract the virus.
So, if a someone gets infected and then visits their (or anyone else’s) grandma or grandpa, aged 80+, who themselves become infected, then the grandparent (based on current estimates) is expected to stand a 1 in 11 chance of dying.
This is deadly serious, literally. If everyone follows the SD/isolation rules then many, many lives will be saved and unnecessary tragedy avoided.
I end with a quote from Professor Michael Osterholm, an internationally recognised expert in infectious disease epidemiology. In a recent online interview alerting all to the risks of Covid-19 he said “I don’t want to scare everyone out of their wits, I want to scare them into their wits.” Poignant, and potentially life-saving, advice.
Please be safe everyone.
Last edited:
