Looking to prevent coronavirus infections imported from abroad, Japan has beefed up surveillance of people quarantining after entering the country.

Despite stringent border controls — from banning new entries, COVID-19 testing upon arrival and a 14-day quarantine requirement — new virus variants have been found in the country, prompting the government to suspect that arrivals may not have been self-isolating as strictly as they should have.

As a result, Japan introduced a new location-tracking app earlier this month to make sure that those quarantining actually do so.