At least five other people had died from the coronavirus in the UK by the time the government reported the first death from the outbreak, new data has revealed.

The figures show that the lethal impact of the outbreak had already been recorded when Boris Johnson joked about shaking hands with hospital staff in the first Downing Street coronavirus briefing on 3 March, when no deaths had been officially announced.

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The first death was not made public until two days later on 5 March, when a woman in her 70s died at the Royal Berkshire hospital in Reading. But the new figures provided to the Guardian by NHS England show that another patient also died that day, at the Pennine acute hospitals trust in Greater Manchester.

It also emerged that the first coronavirus death in the UK occurred on 2 March when a care home patient died, according to details confirmed by Public Health England. This was the first of an additional 3,811 deaths that occurred outside hospitals that were added this week to the the UK’s death toll of those who have tested positive for the virus.

It has also emerged that the first three hospital deaths occurred in Nottingham, Essex and Buckinghamshire on 3 March – the day of the first Downing Street briefing. At the briefing Johnson said: “I was at a hospital the other night where I think there were a actually a few coronavirus patients and I shook hands with everybody.”

Johnson would go on to continue shaking hands with people until at least 9 March, when a fifth victim was publicly confirmed to have died in the UK. The updated NHS England data, shows that 16 people had died by 9 March, including three that day.

Earlier this month, NHS England said its revised records showed the first death occurred on 28 February, but it has now clarified that this was a data entry error. A spokeswoman said: “The actual date of that death was 28 March, and the 28 February had been put in by mistake. The records have been updated.”

She explained that those collating the daily death toll have to rely on data being accurately recorded by individual hospital trusts.

She said: “Data teams are checking in daily with trusts on their deaths. The recorded deaths that we announced every day have generally taken place over the previously three or four days.”

The time lag on reporting the deaths has meant the impact of the virus actually hit much earlier than previously acknowledged. By 13 March, the end of the Cheltenham festival when 68,000 people gathered for the Gold Cup, there had been 51 deaths in English hospitals at a time when only 11 deaths in the UK had been announced.

On the day the lockdown was imposed on 23 March, the government had announced 336 deaths, but by the end of that day there had actually been 802 deaths in English hospitals alone, including 136 that day.