Almost one in three people in Kent could have already had coronavirus, scientists have estimated.

This week the county hit the grim milestone of 100,000 total confirmed positive Covid tests.

But experts from the University of Kent say the true figure could in fact be more than half-a-million.

Prof Martin Michaelis and Dr Mark Wass, from the uni's School of Biosciences, say they are able to make a "reasonable estimation" using the Covid infection-fatality rate.

They calculate that between 184,600 and 553,800 residents have been infected across Kent and Medway, accounting for between 10% and 30% of the total population.

But the bioscientists have issued a stark warning that the high number of cases does not mean the county is set to benefit from any sort of herd immunity.

“Although an increasing number of people have become infected, this does not mean that the pandemic would come to a natural end any time soon," they told KentOnline.

"Recent data from Brazil show that in Manaus the outbreak is still ongoing although more than three quarters of the population have already been infected.

"Moreover, not everybody who has been infected is also protected.

"There is an increasing number of re-infections, some of which are more severe than the original ones, and antibodies, which normally indicate immunity, have been shown to rapidly decline in many individuals after Covid-19 infection.

"The only thing that we do know is that the more people become infected, the more people are going to die.

"If, like in Manaus, 75% of the population become infected, about 460,000 people are going to die in the UK at an infection-fatality-rate of 0.9%, which has been previously determined for this country."

Prof Michaelis and Dr Wass say the more Covid spreads, the more virus mutations are created - such as the new, highly-infectious strain which originated in Kent.

They say if more people develop antibodies, this makes it more likely there will be a "selection pressure" that favours the formation of variants that can bypass pre-existing immunity.

The scientists add: "Therefore, we need to suppress Covid-19 transmission as much as possible."

Prof Michaelis and Dr Wass argue that countries which have suffered fewer deaths have also endured less damage to their economies.

They point out that Taiwan has reported just seven deaths out of population of 23.5 million residents. So far, almost 3,000 people have died out of a population of 1.8 million in Kent and Medway alone.

"Very low Covid-19 numbers make it possible to control outbreaks locally without far-reaching, national restrictions, which then enables the sustainable reopening of the economy," they add.

"Hence, we need to do everything that we can now to get the Covid-19 numbers as low as possible.

"Only following the rules in the current lockdown and avoiding all contacts that are not absolutely necessary will, together with the roll-out of vaccines and increased testing capacities, get us to a kind of normal and give us our lives back.

"As long as the numbers are as high as they currently are, we will have to endure severe restrictions of our freedoms."

How did the scientists calculate the estimated total number of Kent Covid infections?

Prof Michaelis and Dr Wass say the standard approach would be to find out how many people have antibodies. But current systemic data on this is not available.

They say Covid-19 antibody levels appear to decrease quickly "in a significant fraction of Covid survivors".

Meanwhile, the number of positive tests recorded is not a reliable indicator as there will have been many cases that will never be formally diagnosed.

They add: "However, deaths are hardly ever missed, and there are reliable data that estimate the infection-fatality rate for Covid-19, i.e. the percentage of infected people that die from the disease, is between 0.5% and 1.5%."

According to the most recent figures, there have been 2,799 Covid deaths in Kent and Medway combined including 50 recorded within the last 24 hours, the highest daily death rate recorded so far in in the county.

For an infection-fatality rate of 1.5%, this results in 184,600 infections (9.9% of the Kent and Medway population). For an infection-fatality rate of 0.5%, this results in 553,800 infections (29.8% of the population).

The average infection-fatality rate in high-income countries like the UK is 1.15%, according to researchers from Imperial College London.

Under this measure, one in eight people (13%) in Kent and Medway would have already caught coronavirus.

So far, 100,234 of the county's residents (5.3%) have tested positive for Covid. But there was far less testing during the first wave last Spring than there is today.

Health secretary Matt Hancock has said about one in three people with coronavirus are asymptomatic.

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