The BBC have produced a short video guide on the ‘R’ Number

In the news we here that the ‘R’ number is up or down in the covid-19 infection statistics. The ‘R’ stands for the estimate a measure of ongoing transmission. In simple terms the BBC have described the ‘R’ number as a way of rating a disease’s ability to spread.

If the number of people that an infected person passes the virus on to is greater than 1 then this can lead to a rapid, exponential rise. The numbers are a range as they a made up of several factors that will vary from place to place and situation. London has more dense, diverse and higher population.

Ebola, 20141.51 to 2.53
H1N1 Influenza, 20091.46 to 1.48
Seasonal Influenza0.9 to 2.1
Measles12 to 18
SARS-CoV-2 (causes COVID-19)1.5 to 3.5
R0 values by disease type – table courtesy University of Michigan

Measles has one of the highest numbers with a reproduction number of 15 in populations without immunity. It can cause explosive outbreaks – especially in areas of high density population. Another good reason to ensure children are vaccinated against it.

The history of the ‘R’ number dates back to before the 1950s and the research carried out by Ronald Ross his ideas helped the theoretical work of George Macdonald and the empirical work of some of his close associates. The theory for transmission dynamics and control, a deliberately simplified set of concepts, in the “Ross-Macdonald” model plays a role in today’s science.

The latest Covid 19 ‘R’ figures are available by region.

MRC data is publicly available

These figures show the regional Covid-19 ‘R’ values.

The blue lines is show when interventions have been introduced (lockdown on 23 Mar and the relaxation of measures on 11 May), and the red line shows the date these results were produced on 3rd June 2020.

For London, the black line is the median value R=0.95

The lower calculated value for London’s R=0.72

The higher calculated value for London’s R=1.2

The density and diversity of London’s population is high.

Figures for the South West where R is rising and thought to be 1.0 are based on a lower population density overall.

The figures for the North West are worrying as this has a higher density population and a higher number of cases. R=1.01

Although the average national figure for R is less than 1, the regions have different values with London, South West and North West hovering around 1.

There is a margin of error and it looks like we are well within this. Only time will tell whether lockdown was lifted too early.

It is salutary to note that some councils are not expecting their schools to open on Monday 9th June. Tameside Council, part of Greater Manchester has issued a statement citing the rise in the ‘R’ as a reason to change their plans and advise schools not to open.

The Letter from Tameside Council’s Director of Public Health, Dr Jeanelle de Gruchy states:

“Tameside Council understands that this is an extremely challenging time for all who live in our borough but recognises fully the many acts of kindness which local residents have undertaken to support each other. We would like to pay special tribute to the work of headteachers, staff, school governors and childcare providers for their fantastic work in supporting children and families during this and your brilliant contribution to the Borough’s response to Covid 19.

“Nationally, the government is requesting that schools and childcare settings start to increase the numbers of pupils attending over the coming weeks. Our local approach, as you know, has been to focus on making safe and sensible decisions and maintaining, wherever possible collective approaches which can inform local decisions. Headteachers and their staff, in partnership with the Local Authority, have done excellent preparatory work undertaking and completing risk assessments in their schools.

“Members of SAGE (Scientific Advisory Group on Emergencies) and the Association of Directors of Public Health advised caution and concern about the too rapid easing of lockdown and the increased risk of a second pandemic wave. Balancing this concern, the national R number being between 0.7 to 1.0 and estimated at 0.73 in the North West and the importance of having our children back at school, I supported the limited increase in the number of children attending planned in the Borough from Monday 8th June.

“However information released at 2pm today estimates the R value is now above the critical value of 1 for the North West, at 1.01.

“Because of this change in R, and despite the excellent work undertaken, I am therefore strongly advising all schools and childcare settings to delay wider opening until at least 22 June for us to be more assured that the rate of infection is reducing and R is firmly below 1.

“All settings should continue to remain open for vulnerable children and the children of key workers as they have been since the start of the national lockdown.

“I will continue to monitor what is a fast-evolving situation very closely and keep my advice to you under constant review. I will write to you all again next Friday with a further update and advice on wider opening.”

Schools in the NW England change course

Dr Patrick Roach, NASUWT General Secretary, said:

“Employers have statutory responsibilities to protect the health, safety and welfare of their employees at work and to minimise the risks to which employees are exposed. Given the reports that the R rate has now risen above 1 in the North West, meaning that the virus may be growing again, the NASUWT believes these local authorities must fulfil their duty of care to staff and pupils by rethinking plans for the wider reopening of schools in their region.”

“In the absence of new risk assessments being provided to the NASUWT and in the light of the increase in the R rate, the Union must insist that these local authorities demonstrate how they intend to keep pupils and staff safe and if they cannot, they must pause their plans for the wider reopening of schools.”

According to reports in The Guardian, Dr Sebastian Funk of the London School of Hygiene & Tropical Medicine said the UK government appeared to be happy with R floating around 1, despite infections remaining relatively high. “That will come with the risk of higher number of deaths and morbidity compared to a scenario where you drive the disease to lower numbers before loosening the physical distancing measures,” he said.

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