The UK is considering imposing a 14-day quarantine on people who enter the country. Businesses object.

Is such a quarantine useful?

Imposing quarantine on people entering your country makes rational sense for reducing the spread of Covid-19 in two situations, as far as I can see.

• They are coming from countries where coronavirus is more prevalent than it is in your country. In that case, they might transmit the virus more than the people who were already in your country.
• Your country has an effective system of tracing contacts and quarantining people who get exposed. Since you can't track the previous contacts of people who enter, you need to consider they may have been exposed before they came.

Outside of these two situations, quarantining people for entering the country is a pointless nuisance that serves only to help politicians scapegoat foreigners. Maybe that is why Bogus Johnson wants to do it.