Some calculations on coronavirus infection risk

June 26, 2020

We want to know the probability of contracting coronavirus, especially from the viewpoint of someone for whom this poses a significant risk.  We try a top-down and a bottom-up approach.

Top down

The ONS gives an incidence rate of 0.04% per week over the course of their study (from 8 June to 21 June).  So the probability of not contracting CV in a week is (1- 5×10-4)

The probability of not contracting CV in N weeks is (1- 4×10-4)N

The probability of contracting CV in N weeks is [1 – (1- 4×10-4)N]

So this gives results like:


Of course, we would not expect the incidence rate to stay stable in reality, and the probability of any individual becoming infected will depend on their own circumstances.  However, this does indicate that it would be highly desirable to attain a technical solution vaccine, etc to COVID-19 within 100 weeks/2 years.


We start from contact between a susceptible and an infected person.

The prevalence of COVID is about 10-3  ONS data 25 June.

The probability of infection given contact with an infected person is ~ 10-1 [Suggested 5 x 10-2 here]

  • Prob of not being infected in 1 contact ~ (1-10-4)
  • Prob of not being infected in N contacts ~ (1-10-4)N
  • Probability of being infected in N contacts ~[1- (1-10-4)N]



Or we can look at the lower range of this in more detail:


So this obviously raises a number of questions, such as:

i) what level of risk of infection is acceptable?

ii) what level of uncertainty is there in the parameter estimates?

iii)  what exactly is a contact?

What level of risk of infection is acceptable?

This is obviously not merely a question for individual judgement, give the possibility of transmitting infection directly or at many removes to vulnerable individuals.

Confining ourselves to the consideration of individual risk as a first step, we consider the case of a male in his early seventies without relevant underlying health conditions. Data from China gives an infection fatality rate of 4.3% for this group.  UK data shows something like a 2% risk for this group dying in a year.  So let us say our subject wants the risk of dying from COVID to be no more than one tenth of this normal risk.  So we require the risk of infection to be less than 0.05 in round terms, which means our subject should confine himself to about 500 qualifying contacts in a year at the current prevalence.

What level of uncertainty is there in the parameter estimates?

We can consider the question of who the contacts are.  On the one hand, you are more likely to have contact with a supermarket cashier than with a shelf-stacker, and cashiers are likely to have higher prevalence for that very reason—they are in contact with more people.  (Compare ONS treatment of US data.) On the other hand, it may well be that people with [relevant] symptoms have a higher prevalence than those without and are also likely to withdraw from contact. (0NS 12 June).  This could do with further and more systematic treatment.

What exactly is a contact?

This is of course a crucial question.  The latest official UK advice with regard to contact tracing as of 17 June says:

What do we mean by a ‘contact’?

A ‘contact’ is a person who has been close to someone who has tested positive for COVID-19 anytime from 2 days before the person was symptomatic up to 7 days from onset of symptoms (this is when they are infectious to others). For example, a contact can be:

people who spend significant time in the same household as a person who has tested positive for COVID-19

sexual partners

a person who has had face-to-face contact (within one metre), with someone who has tested positive for COVID-19, including:

being coughed on

having a face-to-face conversation within one metre

having skin-to-skin physical contact, or

contact within one metre for one minute or longer without face-to-face contact

a person who has been within 2 metres of someone who has tested positive for COVID-19 for more than 15 minutes

a person who has travelled in a small vehicle with someone who has tested positive for COVID-19 or in a large vehicle or plane near someone who has tested positive for COVID-19

Where an interaction between 2 people has taken place through a Perspex (or equivalent) screen, this would not be considered sufficient contact, provided that there has been no other contact such as any of those indicated above.

So we can take this as a characterisation of the qualifying contacts between two people which might lead to transmission of infection.

Or we can say that R0 = (contacts per day)*(transmission probability per contact)*(number of days case is infective).

So we take Ras about 3, transmission probability per contact 0.1 and  infectious period 10 days, so

3 = (contacts per day)*(0.1)*(10)

So there are something like 3 qualifying contacts per day in a state of nature before imposition of social distancing, which implies a fairly substantial kind of contact.


On the basis of the discussion above, and indeed of common sense, we would say that if you are in a group where COVID-19 poses a significant risk, you should limit your qualifying contacts (with contacts as defined in the contact tracing guidance) as much as possible  unless or until this threatens to do tangible harm to yourself or others.


7 Jews Walk, Sydenham

June 14, 2020


Here are a couple of pictures of 7 Jews Walk, Sydenham. This was the last home of Eleanor Marx, who committed suicide by drinking poison. You have to suspect that she only chose to move there because of the name and that it’s a distorted version of something that has nothing to do with Jews.

This is not so far away from a couple of other radical addresses connected with Iskra and The Red Flag.


As for the name, we believe the Daily Telegraph claimed that it was a corruption of “Doo’s Wharf”, Doo being an ancient place name in Kent. 

Otherwise, a local forum suggests Jews Walk was named after two Jewish brothers who lived in Westwood, a large house on the edge of Sydenham Common, where the Shenewood estate now stands. In about 1769 the brothers obtained permission from Lord Dartmouth, the Lord of the Manor, to create a tree-lined walk across the common from what is now Kirkdale to their house. This walk became known as “the Jews’ walk”. When Sydenham Common was enclosed in the early 19th century the name was retained.

According to the passages of Sydenham and Forest Hill Through Time visible on Google Books,  the Telegraph was lying. There was a building called Doo’s Wharf on the Croydon Canal, but it was named after Henry Doo the owner and anyway later than Jew’s Walk, which was indeed a tree-lined walk leading to the house of David Ximenes, a Sephardic Jewish merchant–the brother may be a Telegraph-style fabrication.


Jews Walk in 1836



Saltburn and slavery

June 7, 2020


UCL have produced a map of the addresses of slaveowners claiming compensation after slavery was abolished in the British Empire in 1834 .   There are not many in Yorkshire, but of these two are rather close to Saltburn.

The Hon. George Heneage Lawrence Dundas of Upleatham Hall, Upleatham, who claimed £4,818 0s 6d as compensation for his freed slaves, also appears to have provided some support for UCL itself in its very early years…

Hmmmmmm not that surprising I suppose. Will not be able to walk on Dundas St without remembering this.

Actually, I was quite surprised since:

(i) you associate Saltburn with the Quakers, who were resolutely opposed to slavery. (But the development of Saltburn as we presently know it dates from 15 or 20 years after these slaveowner payouts, so this is not in fact relevant.);

(ii) there really weren’t that many of these claimants in Yorkshire or the NE–which makes sense, since there were lots of investment opportunities in mines and such closer to home.

In any case,  various things called Zetland (‘noble’ title of the Dundas family) are implicated:


Zetland Court, Dundas Street, Saltburn

Accordion song (Nikolai Yazykov)

April 15, 2020

Oh night, oh night like an arrow fly
Respite is bane to Svyatoslav
He only hungers to win or die
Oh night, oh night like an arrow fly
Respite is bane to Svyatoslav.

Tzimiskes, do you know your shield is strong?
That your chain mail is not delicate?
Our prince cries murder all night long
Tzimiskes, do you know your shield is strong?
That your chain mail is not delicate?

Give swiftest horses to your hordes
Or else our swords will catch them up
And they will not outrun our swords
Give swiftest horses to your hordes
Or else our swords will catch them up.

Boundless is the host you brought
Not many are we, but our blood is Slav
Our blows are sharp and they are fraught
Boundless is the host you brought
Not many are we, but our blood is Slav.

Oh night, oh night like an arrow fly
And fields for victory spread out wide
Rouse up now the warrior cry
Oh night, oh night like an arrow fly
And fields for victory spread out wide.


Nikolai Yazykov (1803-1846)

О ночь, о ночь, лети стрелой!
Несносен отдых Святославу:
Он жаждет битвы роковой.
О ночь, о ночь, лети стрелой!
Несносен отдых Святославу!

Цимисхий! крепок ли твой щит?
Не тонки ль кованые латы?
Наш князь убийственно разит.
Цимисхий! крепок ли твой щит?
Не тонки ль кованые латы?

Дружине борзых дай коней;
Не то — мечи её нагонят,
И не ускачет от мечей.
Дружине борзых дай коней;
Не то — мечи её нагонят.

Ты рать обширную привёл;
Немного нас, но мы славяне:
Удар наш меток и тяжёл.
Ты рать обширную привёл;
Немного нас, но мы славяне!

О ночь, о ночь, лети стрелой!
Поля, откройтесь для победы,
Проснися, ужас боевой!
О ночь, о ночь, лети стрелой!
Поля, откройтесь для победы!


In a series of campaigns against the Kievan Rus’ encroachment on the Lower Danube in 970–971, [John I Tzimiskes]  drove the enemy out of Thrace in the Battle of Arcadiopolis, crossed Mt. Haemus, and besieged the fortress of Dorostolon (Silistra) on the Danube for sixty-five days, where after several hard-fought battles he defeated Great Prince Svyatoslav I of Rus’. (Wikipedia article)


March 6, 2020


A compound adjective that is of inestimable value in daily life, this is indeed used several times in the गीत गोविन्द (Gīta Govinda) of Jayadeva.


With regard to the Gīta Govinda, Krishna is certainly doing some kneading of Radha (milkmaid/female cow herder/cowgirl) in the illustration above, but a pedant could query whether his hands are on her breasts.

Cowgirl. Indeed.

Milkmaid. Female cow-herder. GOPI.

I wonder, is there some implied race fetishism here, inasmuch as Krishna is as black as coal, while Rahda is as pale as the milk she labours over?

The name Krishna apparently means ‘dark blue’. In various artistic conventions (but I know nothing of Indian ones), women are portrayed as light-skinned and men as dark-skinned.

He’s always got his sticky hands all over a milkmaid or three.

Mr Jones, Curzon Victoria 14 February

February 29, 2020



This film started with a typical Ukrainian wooden house in a field of typical Ukrainian wheat and in the house the Ukrainian writer George Orwell is writing Animal Farm.

Apart from that, the action presumably takes place in 1933 when Gareth Jones, who has just been made redundant as Lloyd George’s secretary and has previously succeeded in interviewing Hitler in an aeroplane travels to Moscow in the hope of interviewing Stalin and finding out there the money to pay for forced industrialisation is coming from.  By that stage of course there was a National Government without Lloyd George, so the reference to him and Ramsay Macdonald sorting out the economic crisis made little sense.

Anyway, once in the Soviet Union Jones manages to escape his minder on a trip to Kharkov and tramp round the Ukrainian countryside observing scenes of hunger, death and cannibalism.  He also has to contend with Walter Duranty, the senior foreign correspondent in Moscow, who expounds the official line that there is no famine, really.  Then we get what seems to be an entirely fictional entanglement with the Metro-Vickers trial  and the British engineers being held hostage for Jones’s silence.  Similarly, the idea that Orwell was converted to anti-Communism by Jones’s account rather than his own experiences in the Spanish Civil War is…strange…

So the mingling of fact and fantasy was unsatisfactory, which can leave people wondering about the historicity of the Ukrainian famine.  Another question would be what the actual story is meant to be. If it’s about the famine in Ukraine, then why does it only exist when a Westerner finds out about it?  If it’s about the discovery of the famine, then Malcolm Muggeridge for instance had already written about it.  As the subject of a film, the story of Duranty could have been better, or compare-and-contrast of him and Jones as very able men who could not easily find a place in normal life.


Macbeth, Greenwich Theatre 28 February

February 29, 2020



Picture from Davy’s Wine Vaults/Twitter

The Lazarus Theatre production of Macbeth at the Greenwich Theatre was manly, clear and straightforward, at least when you could make out the words.  (A scene with Macduff’s pregnant wife addressing her bump was almost entirely lost on me, and it was sometimes difficult to understand what Lady Macbeth was saying.)

In line with manliness, the witches were male and as well as having some witchy exchanges cut they wore gas masks in one scene,  The direct approach meant that the pace of the action and there was on occasion the feeling that the cast just wanted to get it over with quickly.  There was no real distinction between the external world of action and heroism and the inner one of evil, obsession and femininity.

Tomorrow and tomorrow and tomorrow raised a small shiver at the end, while Macbeth’s address to sleep was rather thrown away as he busied himself with washing off blood.  The murderers waylaid Banquo in complete darkness, rather contrary to their own words on the occasion.  Duncan became simply a comic figure at times.  The scene where Malcolm relates his imaginary failings to Macduff was even more tedious than normal, though that probably can’t be helped.

It was one of those productions where you can ask yourself what they are quarrelling over–if there is no glory, magnificence or colour (apart from Lady Macbeth’s dress) then what is the point.  But it will have been useful in helping anyone studying the text for an exam remember who the characters are and what they do.

Oedipus King, Theatro Technis 18 January

January 19, 2020



Overexposed picture I acquired from Twitter

They are certainly very nice people at Theatro Technis, and go out of their way to make you feel part of the family.  At the end of the production, director George Eugeniou made an affecting appearance to thank the audience and to point out the contemporary relevance of the play.  His idea was that Sophocles had reflected in Oedipus the character of his friend Pericles, who had done much good for Athens but also lead it down the road of empire.  And now our world was beset by charismatic, dishonest leaders like Trump, Erdogan and Boris Johnson.

As for the production itself, there was some effective direction in for instance the reaction of individual chorus members to the news of Jocasta’s death, and the creation of striking stage pictures, as in the stolen and overexposed picture above.

BUT it was very difficult to make out what any of the actors were saying, even the native speakers of Standard English, so anyone who did not already know the piece would have been baffled.  ALSO the curse of naturalistic acting, when what was needed to stand and deliver (clearly!) ALSO the chorus neither danced nor sang.  ALSO there should have been some indication that Oedipus and Jocasta are King and Queen and so set apart.  ALSO the translation by Don Taylor depressingly combined inexactness with the bureaucratic-colloquial register.  ALSO the family feeling included audience members recording proceedings on their mobile phones, which distracted me at least.

Twelfth Night, Brockley Jack 16 January

January 17, 2020



As far as we know, this comedy was first performed on the sixth of January (the twelfth day of Christmas) 1601, while in the play Antonio advises Sebastian

In the south suburbs, at the Elephant,
Is best to lodge (III.iii.39-40)

So Brockley on the 16th of January was pretty close both in time and space, and appropriately enough this production was very much mainline pub theatre Shakespeare.  In particular, ID tags, mobile phones and messages from electronic devices were very much in evidence.

At the beginning I was just alienated by the people rushing around but then I was drawn in by the poetry and the combination of absolute beauty with absolutely accurate psychological insight.  I enjoyed the boyish charm of Jessica Kinsey playing Viola playing Cesario.  The character of Feste was elided, so his machinations fell to Maria, while Olivia was very much a no-nonsense North Country lass who seemed to be mourning as a matter of form to pass the time.

The audience laughed or at least chuckled quite frequently, which is far from a given at Shakespeare comedies, and this was a very reliable performance of a very reliable comedy.

But what interested me was Olivia with her hard-bitten morning and her name that contains ‘Viola’, as does Malvolio’s name.  First of all, I thought that as in some kind of student clique Olivia (I, Viola) was trying to get in on the sibling mourning thing, while Malvolio (Viola, olm)  was trying to get in on Olivia, just not very adroitly.

Then I decided that in fact this was all an hallucination of the drowning Sebastian, where he fantasises Olivia as a longed-for ideal of salvation but Malvolio (who remains unreconciled) serves a a reminder that all is not well.  In fact, Sebastian is deluded and confined like Malvolio but in a watery grave.

When Malvolio says

I will be revenged on the whole pack of you! (V.i.380)

he will indeed, for they are all dead…

Antigone, New Diorama Theatre 1500 11 January

January 12, 2020



This was the story of Antigone reflected in the world of two girls too young to go drinking.  I found that painful, with the heroism and beauty of the original dismissed without hope of appeal and what felt like a lot of overextended improvisation of sisters arguing and sistering.  They occasionally got to imitate some other characters as well.

I just about managed to last out an hour by concentrating on Ismene’s spangly sneakers and counting the number of people in the audience and fantasising about a clear run to the doorway.

Once again somebody had missed the point that tragedy is about things happening to people who are adults and are able to comprehend and react to events as adults.  That is tragic, bundles of suffering crushed by the incomprehensible is just disgusting.

After Antigone’s death there followed what I thought was a rather affecting momologue by Ismene covering first sexual experience, marriage, childbirth, social obligations, widowhood, being left unoccupied in a big house.  It would have been better if the actress had spoken more clearly.

So then I thought the playwright wanted to ask what a woman’s life is for.  First of all Antigone tries to be like a man and act in the world and then Ismene although damaged experiences family life and a husband and going to ceremonies with relatives, but all the will and intellect is just the emptiness of unused rooms.

I quickly made my way to the NDT unisex toilets, and then home.  See also  Greek Drama in London 2020.