Parties and a lack of social distancing over Christmas and New Year are among factors that will cause coronavirus infections to spike, a top public health official has said.

Jim McManus, Hertfordshire’s director of public health, said there is “no doubt” that there will be a spike in cases from the festive and New Year period, with people having “eased into unsafe behaviours”.

Multiple New Year parties were shut down by Hertfordshire Constabulary, with Chief Superintendent Matt Nicholls estimating that police were called to between 40 and 50 in the county.

Mr McManus said people getting too close to one another and gatherings in the "last gasp before we went into lockdown" will have caused cases to rise.

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Speaking in a Covid-19 press briefing today (Wednesday), Mr McManus said: “In terms of the numbers, I think there is no doubt that there will be a spike from the Christmas and New Year period, including New Year’s eve.

"We know there were some people having house parties. We also know a colloquial report from some supermarket workers who said that the alcohol aisle in one or two places was chaos because people were kind of mixing and that’s enough mixing to pass the virus.

"There were also people in Hertfordshire who went to demonstrations and got close to people and didn’t wear masks and even outdoors that is enough to transmit the virus.

"We’ve also seen people congregate in a number of play areas in large numbers with no social distancing.

"I think the general thing is we have eased into unsafe behaviours and Christmas and New Year has definitely fuelled that and it is showing in the numbers as they are continuing to rise despite the fact that we should have all been at home on Christmas and New Year.

"It will take at least a week before that curb is turned."

Speaking about patrolling New Year’s Eve, CI Nicholls said it was “quite complex” from a policing point of view.

He said police resources were largely geared up for house parties.

He said: “Normally our focus will be on nightclubs and bars and our general hotspots on New Year’s Eve would be Watford, parts of Stevenage and Hertford.

"So, it was a difficult one to call and plan for. But obviously over the course of summer to autumn there had been unlicensed music events and some of these have been reported globally, particularly a large one in France.

"So, we were making sure that we did not have any large-scale unlicensed music events and we were studying social media very closely around that and we also put out to the general population what sort of things to look for in order to prevent those things from happening.

"We were called to a number of house parties, in my head I have got somewhere in the region of 40-50 across the evening. There may have been more going on, but these were the ones that were sufficiently annoying to other people that would have led to them calling us and for us then dealing with them.

"But generally new year from a policing perspective passed off relatively peacefully."