The Christmas risk of Covid is ‘difficult to control’

If the majority of UK households flock together in ‘bubbles’ for the Christmas holidays, coronavirus infection rates could be difficult to control.

That’s the warning from the scientists who model the possible spread of the virus over the five-day period.

In England, Scotland and Northern Ireland, the rule is that three different households can temporarily meet under one roof, whereas in Wales only two are allowed.

But there is mounting pressure on ministers to change that policy, amid fears of an increase in cases.

Last month, a report from government scientific advisers warned that the number of infections could easily double over the course of the hiatus.

Studies have shown that the coronavirus spreads most easily in crowded and congested rooms where people are together for long periods of time, a typical setting for Christmas gatherings.

And the greater the spread of the virus in the community, the greater the chance that someone in a family gathering will become infected, possibly without realizing that they have no symptoms.

In recent weeks, teams of scientists across the UK have been trying to get a better idea of ​​the potential impact of loosening the restrictions.

But it is a difficult task without exact answers, because it all depends on how people choose to spend the next few days, and that is impossible to predict.

Scientists at the University of Bristol studied the implications of the bubbles themselves and the effect of the joining of different households.

And the first results, yet to be formally published, indicate that the fewer people who take the option of forming a bubble with others, the better, from the point of view of containing the disease.

If a one-person household joins another household of any size, the impact on infection rates would be marginal, they suggest.

But if all UK households were paired with each other, each bubble would contain an average of 4.7 people.

That would lead to a reproduction number (R) within households between 1.9-2.4.

And an R number above one means that the disease is increasing.

If only half of UK households join a bubble, it could still increase the R number by 30%.

The Bristol modelers assessed the implications of all households in the country opting for the maximum allowable Christmas mix, forming a bubble with two other households.

In that case, there would be an average of just over seven people in each bubble.

And the R number would rise to 2.84-3.55, suggesting a rapid rise in infections.

The research concludes that everyone who joins a Christmas bubble “has the potential to make transmission extremely difficult to control.”

According to team member Dr. Ellen Brooks-Pollock, understanding the scale of the risks will help them figure out the best way to respond.

“It is important to be as honest as possible about the results of the analysis work that we have done,” he says.

And it’s easy to imagine a kind of terrible scenario.

“But really, when you start modeling it, you can start to think about how you would balance these higher risks elsewhere.”

House bubble formation “should not be encouraged in general,” says Dr. Brooks-Pollock.

If people don’t really need to reunite with another household, it would be helpful if they didn’t.

And if they do, they should minimize contacts with people outside the bubble as much as possible, to prevent them from contracting infections while together at Christmas and then spreading the virus to friends and colleagues when they return home in other parts of the UK.

Scientists at the London School of Hygiene and Tropical Medicine have been investigating the likely scale of social mixing over the Christmas period.

Having schools and many workplaces closed at that time should help reduce the number of infections overall.

But greater social interaction in households will have the opposite effect.

The key to the effect on infection rates will be how well people limit their interactions before entering their Christmas bubble.

“There is a great risk during Christmas of essentially a transfer of infection from younger groups with more contacts to older groups that do not usually have this level of mixing, especially in this type of year,” said Dr. Adam Kucharski , associate professor at LSHTM, says.

“Even in normal years, we see an increase in hospitalizations for diseases like pneumonia after the Christmas period.

“And the kind of intergenerational mixing that we see during this Christmas break is likely to contribute to that, because we basically have groups with very different risk profiles who mix in ways that they don’t usually mix.

“What will happen when we get to January is very difficult to predict because it is a very unusual year.

“But it all depends on how exclusive and big the gatherings are and how careful the people are before and after Christmas.”