When the next pandemic hits – and it’s a question of when, not if – it will be vital that we did all we could at this moment to learn the lessons taught to us by coronavirus. One key lesson has been the effectiveness of travel bans. Countries that managed to contain the virus effectively implemented immediate health screenings of new arrivals, 14-day quarantines for those entering the country and even full travel bans. Of the world’s population, 91% live in countries with current travel restrictions, and 39% of people live in countries whose borders are completely closed to non-citizens and non-residents. In mid-March Australia noted that 80% of cases being detected were linked to returning travellers. The government quickly introduced a border-closure policy in which only nationals were let into the country, who then needed to spend two weeks in mandatory quarantine in a hotel room. Despite the cost to the economy, roughly $4bn per month from international travellers and $5bn from domestic travellers, who are restricted from crossing state borders, the government felt it was imperative to get a handle on the number of new cases. This policy has paid off with a complete crunching of the coronavirus curve: Australia has had 102 deaths, and has only a handful of daily new cases. Life is slowly returning back to normal, with thethreat of coronavirus pushed beyond its borders. A similar story can be told about New Zealand, Greece, Iceland and the Faroe Islands. The UK is implementing its own restrictions, but what took us so long? To understand this delay requires a delve into the minutes of Sage (the Scientific Advisory Group for Emergencies) that the government points to as evidence of it “following the science”. On 3 February and 23 March travel restrictions were discussed by Sage but were seen to have a negligible effect. Modelling noted that “if the UK reduces imported infections by 50%, this would maybe delay the onset of any epidemic in the UK by about 5 days; 75% would maybe buy 10 additional days; 90% maybe buys 15 additional days; 95% maybe buys a month.” This fits with Sage’s initial advice from January to March to develop a strategy based on the 2011 Pandemic Flu Plan. It recommended that coronavirus be treated like the flu and allowed to spread, while keeping the number of cases within the NHS’s capacity and protecting the elderly and vulnerable. Therefore travel bans were seen as only delaying the inevitable spread of the virus within the UK, and thus not worth the associated disruption and economic cost. When the UK went into lockdown on 23 March, people living within the country were instructed to stay home and not travel farther than a few miles from their homes and only for essential journeys. At the same time, passengers from countries such as Italy, Spain, New York, Brazil and Russia could arrive at Heathrow and take the tube straight into London with no checks, screening or monitoring. It is ironic that the government that ran on “taking back control of our borders” was so reluctant to implement border controls when they were actually needed to protect its citizens and residents. The current UK plan to quarantine all arrivals (except a small group of essential workers) for 14 days feels three months too late and too blunt an instrument. To stop the outbreak and limit the number of people exposed to the virus, the UK government should have moved quickly in late February/early March to implement border closure while moving to an early lockdown. This would have limited the number of imported cases, provided time to aggressively go after the virus through testing and tracing anddrive down numbers to the dozens. Under the new plans, arriving passengers and crew must self-isolate at their homes or a specified location. They are only permitted to leave the house to buy food or medicine, attend funerals and court hearings, and to access public services. This will be monitored by unannounced visits and a breach would result in a £1,000 penalty. While the overall idea to monitor importation of new cases is indeed a valid one that has been endorsed by the World Health Organization as countries exit lockdown, the implementation is problematic. It would make more sense if quarantine was mandated only for those arriving from countries with much higher rates of infection, and notthose that have a marginal number such as Greece, Australia, Norway, South Korea, Taiwan or Denmark. In addition, we should follow the example of countries such as Greece, Singapore, Hong Kong and Austria and test for Covid-19 on arrival. At this stage, minimising the number of imported cases should be a priority. But what should we do when the next pandemic hits? The key learning must be the need to halt the export of the virus at the early stage of the outbreak. In January 2020, China could have closed its borders once it became clear that coronavirus was spiralling out of control. The country clearly had sufficient resources, personal protective equipment, hospitals and health staff to manage the outbreak without external assistance. Instead, it delayed closing borders and as a result, coronavirus has infected more than 6 million people across 188 countries. In a highly globalised economy closing borders may seem unpalatable, but perhaps we have now learned our lessons the hard way. • Prof Devi Sridhar is chair of global public health at the University of Edinburgh