The baby was delivered at North Middlesex Hospital, in Edmonton, north London (Picture: Press Association)

A positive coronavirus test of a newborn baby has raised concerns over the way the infection is transmitted, according to a virology professor at Imperial College.

The child tested positive for Covid-19 at North Middlesex Hospital, in north London, shortly after being delivered and became the youngest person to be diagnosed with the disease in the UK, the Sun reported.

The mum was also found to have coronavirus.

Professor Richard Tedder, Visiting Professor in Medical Virology, Imperial College London, said the news raised concerns about the potential ways in which the transmission may have occurred.

But he urged caution and said the positive test did not necessarily mean the child had Covid-19.

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Prof Tedder said: “It is important to say at this point in time that the detection of Covid-19 nucleic acid on the sample from the child does not necessarily mean that the child was infected.

“It could well have come from the mother at the time of delivery, further follow-up of the infant will clarify whether or not the infant is infected.

“Previous data from colleagues in China, published in the journal The Lancet, albeit on a small number of mother and infant pairs, did not show infection in any of the infants at the time of birth.

“Neither did sampling of breastmilk immediately after birth contain detectable virus.

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A man wearing a mask stands in an underground train in London (Picture: Getty)

Prof Tedder added the hospital’s observation of a possible neonatal transmission is unexpected and needs further confirmation.

He said the question of risk to a newly born child being nursed by a mother who is known to be infected is a matter that will need careful consideration.

North Middlesex university hospital NHS trust said in a statement: “Two patients at North Middlesex university hospital have tested positive for coronavirus.

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“One has been transferred to a specialist centre and one is being treated in an isolation room.

“The safety of our patients and staff is our top priority, so in following guidance from Public Health England, we are regularly deep cleaning the areas where the patients are cared for and staff who were in close contact with these patients were advised to self-isolate.”

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Ten more patients have died in England since Friday after testing positive for Covid-19.

The UK death toll now stands at 21, with 20 deaths confirmed in England and one in Scotland.

The patients were being cared for in Buckinghamshire, Sandwell & West Birmingham, Wolverhampton, Leicester, Barts, London, north Middlesex and Chester, NHS England said.

A number of the victims, who were over 60, had underlying health conditions.

There have been 1,140 positive tests for coronavirus in the UK as of 9am on Saturday, up from 798 at the same time on Friday, the Department of Health and Social Care said.