Employees sit at their desks beside empty spaces as part of protective measures against the spread of the coronavirus, at the offices of Hyundai Card credit card company in Seoul, South Korea, April 9, 2020.
  • An effective way to reduce coronavirus infection risk is to create a "social bubble," a new study suggests.
  • The research evaluated three common contact-reduction strategies: interacting solely in small social bubbles, seeing only people with similar characteristics such as geographical closeness or age, and only interacting with friends and family who know and regularly see each other.
  • Interacting in small social bubbles was the most effective, though the most difficult.
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On Monday, a county in the San Francisco area in the US implemented new health guidelines that instruct residents to form social circles of up 12 people with whom to socialise. The Alameda County recommendations require a group commitment - all members can only see each other - and stipulate that interactions should still be outside only. Residents are being told to maintain the same bubble for three weeks at a time.

This "social-bubble" approach to curbing the coronavirus' spread is effective, according to a recent study published in the journal Nature Human Behavior. The researchers evaluated the impact that three types of reduced social contact have on the virus' ability to spread. The best strategy, they found, is to restrict interaction to a few repeated contacts, each of whom also only see the same bubble members.

Some people have already been using this strategy, forming "pods," "isolation cells," or "quaran-teams."

"These micro-communities are difficult for a virus to penetrate and - importantly - if the infection is contracted by one contact, it is difficult for the virus to spread much further," the researchers wrote.

'More moderate contact-reduction policies'

The researchers, a team from the University of Oxford and University of Zurich, wanted to figure out how to most effectively minimize coronavirus infection risk while still allowing some in-person interactions to resume.

"Adverse social, psychological and economic consequences of a complete or near-complete lockdown demand the development of more moderate contact-reduction policies," they wrote.

The first of the three strategies they analyzed involves seeing only contacts who have similar characteristics to you - for example, people within a small geographic region or one age group. In this model, people might only work near co-workers who also live in their neighborhood.

The second would have people see only those in their circles who regularly see one another. Since individuals usually have a number of groups - family, friends, co-workers - this strategy restricts one's interactions to only people who have contact with others in the network. Say your co-worker is also friends with your cousin and they interact, you can see both of them.

The third strategy creates a "social bubble," limiting one's interactions to a small number of repeated contacts. This means intentionally choosing a small group of people who only see one another. For example, that might mean choosing one other family for your family to interact with, and agreeing that nobody would see other family or friends outside of the group. (The researchers did not give a specific number of people that would be most effective in the bubble.)

"This strategy relies on a strategic decision to form the most convenient and effective bubbles, and restrict contact to within this bubble over time," the researchers wrote.

The bubble strategy would cut the risk of infection most, they found.

But the authors noted that "all three of our strategies substantially slow the spread of the virus" compared to situations with either no deviation from the norm or a random approach in which people did not follow a specific strategy and instead made random choices about who to see and when.

A strategic social bubble breaks the transmission chain

Forming a social bubble works best, according to the recent study, because it cuts down the number of people you come into contact with.

The researchers used social-network and infectious-disease models to calculate the infection rates that would result from each of the three strategies in groups of individuals that ranged from 500 to 4,000 people in size. The social-bubble strategy, they found, resulted in 30% fewer infected individuals than the randomized strategy. The strategy of group ties resulted in 19% fewer infections, and the "similar-characteristic" network strategy resulted in 2% less.

However, the social-bubble system is the most difficult to follow, the researchers said, because it "requires coordinated action of everyone involved in a given bubble."

They added that "since most individuals in a post-lockdown world need to interact across multiple social circles (for example, workplace, extended family and so on), employing only one strategy might not be practical."

A mix of strategies could be more realistic and still effective, they added.

"Each combination performs better in limiting infection spread" compared to the randomised approach to social contact, they wrote.

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