The proportion of Covid tests coming back positive in England has soared throughout July, with just two councils now within a safe limit set by the World Health Organisation
It comes as a drop in cases in recent days has prompted hope that the current wave of infection has peaked.
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UK government data shows there was a 5.8% decrease in recorded coronavirus cases in the seven days to 22 July compared to the week before, falling from 267,492 positives to 251,968.
But analysis by NationalWorld has found the number of people taking PCR tests has also fallen by 5.8%, with the proportion of those that received at least one positive result in that week-long period climbing from 10.4% to 10.9%.
Pandemic considered out of control
Last year WHO recommended that governments should ensure the proportion of coronavirus tests coming back positive remains below 5% for at least two weeks before regions reopen.
The threshold is the maximum limit at which point a pandemic would be considered out of control, although positivity rates would ideally be far lower.
The rate is now greater than 5% in 313 out of 315 council areas. That is up from 304 a week earlier. Only Breckland, in Norfolk, and Somerset West and Taunton are now below the threshold.
Past the peak?
England’s positivity rate has climbed rapidly throughout June and July. In the seven days to 24 June it stood at 3.8%, rising to 5.9% in the week to 1 July and 7.6% in the week to 8 July.
The rate has fallen since reaching a peak of 11.8% in the seven days to 19 and 20 July, falling for two consecutive days since, although fluctuations in testing on different days of the week can always affect comparisons over periods that are not like for like.
A total of 2.41 million people were tested in the seven days to 22 July, during which time 251,968 positive cases were recorded.
The seven-day rolling number of cases has also fallen since a peak of 307,007 on 19 July – but the positivity rate remains higher than a week ago.
Overall Covid case numbers also include lateral flow tests, whereas the positivity rate counts the more accurate PCR tests only. The positivity rate removes duplicate tests for the same person.
The positivity rate increased in every region in the latest week except for the North East, which currently has the highest rate at 16.4%.
The North East has also seen the biggest drop in tests carried out – down by 16.5%, from 144,935 in the week to 15 July to 121,029 in the week to 22 July.
Overall, 214 out of 315 councils saw a rise in their positivity rate in the last week – 78 of which saw a simultaneous drop in recorded cases.
What has WHO said?
WHO set out its 5% threshold in May last year, long before effective vaccines had been developed and rolled out.
The positivity rate threshold should be used to supplement estimates of the R-number – the rate of the virus’s transmission in communities – to assess whether the epidemic is under control, it said.
In England, 88.1% of adults had received at least one vaccine dose as of 26 July.
NationalWorld has asked WHO if successful vaccination programmes would affect its guidance on test positivity. It has not yet responded.
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