Shutting Britain’s borders at the start of coronavirus could have prevented major outbreak
Shutting Britain’s borders at the start of coronavirus’s first wave could have prevented major outbreak, another study suggests
- Academics looked at 162 countries and estimated the number of imported cases
- Found travels bans are most effective in countries with low Covid transmission
- Also benefit countries ‘close to a tipping point’ in their epidemics, with an R of 1
Shutting Britain’s borders at the start of the coronavirus crisis may have lessened the country’s catastrophic outbreak, another study has suggested.
Researchers from the London School of Hygiene and Tropical Medicine (LSHTM) modelled the impact of international travel restrictions on the spread of Covid-19.
They looked at 162 countries and estimated the number of imported cases, which scientists will never know for certain due to a lack of testing early in the year.
They found travels bans are most effective in countries with low transmission, or that have strong travel links with countries recording high rates of infection — but that they had a ‘limited impact’ in nations where the virus is already prevalent.
The UK Government blocked all travel to and from China in early February, a move which experts say undoubtedly prevented some cases of Covid being imported. But No 10 was criticised for not putting any travel restrictions on people coming from Italy or Spain, where infections were rocketing.
LSHTM academics said bans can also stop outbreaks from spiralling out of control even if they are enforced in countries ‘close to a tipping point’. These are nations which have a reproductive ‘R’ value – the average number of people each Covid patients infects – of between 0.95 and 1.05.
This could, in theory, have huge implications for Britain’s current situation – because officials believe the UK’s R is between 0.8 and 1.0 currently.
But there are no rules in place preventing people in England from travelling abroad – although holidaying Brits must quarantine when they return home.
Risk rating by country, in the absence of international travel restrictions. Scenario A estimates how many imported cases would arrive in each country if there were no travel restrictions, while scenario B factors in bans introduced this spring in light of the crisis. Scenario C and D do the same for September
This is how much countries in Europe would need to reduce international travel to bring proportion of total incidence due to imported cases to less than 1 per cent. Error bars represent the lower and upper 95% credible intervals of our expected number of imported cases estimates
Travel bans are unlikely to be effective when the virus is already spreading rapidly within a country, the LSHTM researchers said.
Writing in the study, the team led by Professor Mark Jit, an epidemiologist at the university, said: ‘Countries can expect travellers infected with SARS-CoV-2 to arrive in the absence of travel restrictions.
‘Although such restrictions probably contribute to epidemic control in many countries, in others, imported cases are likely to contribute little to local Covid-19 epidemics.
‘Stringent travel restrictions might have little impact on epidemic dynamics except in countries with low Covid-19 incidence and large numbers of arrivals from other countries, or where epidemics are close to tipping points for exponential growth.
‘Countries should consider local Covid-19 incidence, local epidemic growth, and travel volumes before implementing such restrictions.’
Professor Jit added: ‘We recognise these measures carry a high economic and social cost, so it’s important that governments use travel restrictions in a targeted way.’
The authors used detailed flight data to estimate the number of imported Covid-19 cases and compare it with infections in 162 countries.
The authors produced estimates of international travellers in May and September 2020 based on two scenarios.
One scenario used flight data for the same months in 2019 and the other scenario was based on the expected reduction in passenger numbers.
Numbers of Covid-19 cases and infection rates were estimated using a mathematical model that factored in asymptomatic and unreported infections.
Where imported cases accounted for more than 10 per cent of cases within countries, international travel was blamed for proliferating Covid’s spread.
When imported cases accounted for less than 10 per cent, their impact on the growth of the epidemic is usually small.
Travel bans would have an almost undetectable effect on epidemic size in countries where imported cases accounted for fewer than 1 per cent of infections.
The team said their findings showed that the international travel bans enforced worldwide in spring were ‘justified’ because most cases were coming out of China.
They wrote: ‘In May, 2020, imported cases would have contributed to more than 10 per cent of total incidence in the majority of countries without travel restrictions, and hence such restrictions appear to have been justified.’
Professor Neil Ferguson, dubbed ‘Professor Lockdown’ after his gloomy modelling spooked Number 10 into enforcing the first national shutdown, told MPs over summer that a lack of screening at airports was the route cause of Britain’s catastrophic outbreak.
Professor Ferguson said thousands of infected people were allowed to fly in from Europe and spread the virus through the UK.
Professor Ferguson told MPs: ‘We tried very hard to estimate what proportion of cases were being missed. At the time [before lockdown] we didn’t have a policy of screening people at borders and we estimated then that two-thirds of cases were being missed.
‘What we know now is… it’s probably 90 per cent of cases imported to this country were missed.
‘These were really decisions made by the Foreign Office and by the Department of Health and Social Care, not by SAGE.
‘SAGE recommended that when a country had been identified as having active transmission, we should check travellers from those countries.
‘The difficult was we know now, particularly with Spain and Italy, had large epidemics before they even realised. We were just not aware of the scale of transmission in Europe.
‘Had we had the testing capacity then certainly screening everybody with symptoms coming in would’ve given us a much better impression of where infections were coming from.’
