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expert reaction to latest R number and growth rates published by the government and latest data from the ONS Infection Survey

The government have released the latest R number ad growth rate estimates, and the Office for National Statistics (ONS) have released the latest data from their Infection Survey. 


Commenting on the ONS Infection Survey:

Prof John Edmunds, Professor in the Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine, said:

“The ONS survey gives us a unique insight into infection in the community.  The numbers are small and so difficult to interpret at times.  However, the slight increase in prevalence of the virus that has been picked up by the survey echoes increases in cases and test positivity that we have observed in the reported cases.  Together, these are worrying signs that require action to be taken to reverse the trend.”


Commenting on the ONS Infection Survey:

Prof Sheila Bird, Formerly Programme Leader, MRC Biostatistics Unit, University of Cambridge, said:

“The design of the ONS Infection Survey for England is such that most recent two-weeks [13 to 26 July] for which the estimated average number of new individuals infected per day was 3200 (95% CI: 1700 to 6000) is based on around 24,000 person-weeks of follow-up during which 10 new infections occurred.  By contrast, incidence during each of the four previous fortnights was based on 40,000 to 60,000 person-weeks of follow-up.  Even so, the centrally estimated incidence doubled in the most recent fortnight compared to the preceding 2-weeks (up from 1500 to 3200, p ~ 0.08) which is alerting.

“The counter-weight that hospital admissions for COVID-19 disease have not yet increase is light-weight for three reasons: first, there is a delay between infection and progression to hospitalisation; secondly, some of the newly swab-test positive infections in the ONS Infection Survey will never become symptomatic – and likewise a similar proportion of the 3200 new infections daily in the community in England but these asymptomatic infected persons are capable of transmitting the virus; thirdly, we need to know more about the demography (age, sex, ethnicity) of the newly infected persons in the ONS Infection Survey as disease progression and hence hospital admission are less likely for younger infectees.”


Dr Yuliya Kyrychko, Reader in Mathematics, University of Sussex, said:

“The headline R number for England is estimated to not have changed much since last week.

“However, since it takes time for actual changes in epidemic levels to translate into notable changes in people developing symptoms and requiring healthcare, this suggests that the situation is very close to a possible growth in the number of cases in the near future.

“This is further supported by the facts that in the North West and South West estimates of R number have increased since last week, with the latest estimates indicating that the R number can be above one in those regions.  This explains why overall SAGE is not convinced that the overall R number is below 1 in England at the moment.”


Dr Konstantin Blyuss, Reader in Mathematics, University of Sussex, said:

“A seven-day rolling average shows that the number of daily new cases in the UK is steadily increasing over the last two weeks.

“Taken together with latest ONS estimates of around 4,200 new cases each day this past week, this indicates that additional care, and possible further containment measures may be required to mitigate this growth in cases and reduce the potential of a large second peak.

“Since this infection is mostly spread through direct human contact, it looks unavoidable that, at least locally in the regions exhibiting highest growth in cases, some of the lockdown measures, and potentially some additional restrictions on travel between regions may have to be reintroduced.”


Dr Daniel Lawson, Lecturer in Statistical Science, School of Mathematics, University of Bristol, said:

“There is no such thing as a ‘slight’ increase in infection rate.  Either the infection is under control with the reproduction number below 1, or if it is greater than 1 the infection will spread rapidly through the population.  The ONS survey data provides some evidence of an increase.

“But there is a difficulty in measurement.  When cases are low, the average reproduction rate can still be below 1 but we can see an increase in cases by chance, because cases tend to occur in bursts within a community, which should be captured if test and trace systems are working.  We can also see an increase in cases by changes in testing or reporting.

“Decisions must be made in the face of this uncertainty, such as the announcement that the UK is pausing easing.  Evidence from Europe implies that we should take the apparent increase seriously, as acting too late can make lockdowns longer and increase mortality.

“The UK is clearly close to the tipping point in which the infection grows.  Whether local lockdowns and other actions are enough is as-yet unknown.  We should be prepared for further rapid action to prevent the infection from getting out of control again.”



R and growth rates:

ONS Infection Survey:


All our previous output on this subject can be seen at this weblink:


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