3 different coronavirus R rates in one afternoon. What's going on in the UK?
It’s beyond doubt that coronavirus has started to spread more quickly in recent weeks.
As a consequence, Boris Johnson has made social gathering rules even stricter across the country. Birmingham has also become the latest area to be subjected to stricter local lockdown rules, with households banned from mixing with each other.
Liverpool has also been added to the coronavirus watchlist of areas of concern after a four-fold rise in confirmed cases.
According to the government, the coronavirus R rate across the UK has risen to at least 1 in all regions. It’s weekly update - which happens every Friday afternoon - says the range is between 1 and 1.2.
The R rate value shows the average number of people each COVID-19 positive person goes on to infect, and is hard to measure exactly. When it is above 1, it is a strong indication the virus is spreading.
Today, however, observers of the R rate may also have noticed two other R rates. One study from Imperial College London, which said it could be as high as 1.7.
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There have also been reports the rate could be 1.3, based on unofficial data from a government-funded app in which users self-report Covid-19 symptoms.
This is how each of those different estimates have come about.
The government’s estimate
The official estimate that the UK’s R is between 1 and 1.2 was released on Friday, following a week of new daily infections totalling more than 2,000 a day.
The government says it uses a “range of data” to estimate R and the virus’s growth rate.
It uses epidemiological data such as admissions to hospital and intensive care, as well as deaths. This can result in a three-week lag because of the time it takes for a person to become infected and later end up in hospital after developing complications.
Surveys assessing people’s behaviour are also used, which can be quicker to feed into new R rates but rely on self-reported behaviour and make assumptions about how the information relates to COVID-19’s spread.
Household infection surveys, where people are given swab tests, also feed into the data.
Different models are then produced and the government uses those to produce an estimated range of the R number, with the true value likely to be somewhere within that range.
A study released today suggested England’s cases have been doubling every seven to eight days since 22 August.
Scientists at Imperial College London examined test results from more than 300,000 volunteers between 24 July and 7 September – the country’s largest study into the coronavirus outbreak.
They believe that 13 in 100,000 people in England had the coronavirus, compared to four in every 10,000 between 24 July and 11 August.
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The study suggests R is at 1.7 – higher than the official estimate.
The University of Reading’s Dr Simon Clarke said: “If the R number is as high as 1.7, as this data suggests, then we could be at risk of being almost back at square one in terms of our ability to contain the virus.
“This is a massive blow to the government’s strategy to contain the spread of COVID-19.”
The government has reacted to the rise in cases this week by banning gatherings of more than six in England.
Prof Paul Hunter, Professor in Medicine, UEA, said the results were of “particular concern” adding it “may not be many days before case numbers exceed those seen in May.”
Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading described the study as “a massive blow to the government’s strategy”. He added: “It’s likely that the coronavirus is circulating more freely out in the community again.”
A third study out on Friday placed the R value at 1.3 in England, 1.2 in Scotland and Wales and 1.1 in Northern Ireland.
The unofficial data was drawn from a government-funded app by health science firm Zoe in which users can self-report coronavirus symptoms. Analysis is then provided by King’s College London.
According to the Mirror, the study suggested 35,248 people have symptomatic COVID-19, up from just over 22,000 last week, with the UK averaging 3,610 cases each day in the two weeks to 6 September.
The 1.3 estimate for England is just above the government’s figure for the same country, which is at most 1.2.
Coronavirus: what happened today
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