Travel restrictions effective in countries with low number of COVID-19 cases: Lancet study

Travel restrictions are effective in countries with low numbers of COVID-19 cases, or that have strong travel links with nations experiencing high rates of viral infection, according to a study published in Lancet Public Health journal.

study also suggests that travel restrictions may have been most effective during early sts of pandemic, and measures are unlikely to be effective when virus is alrey spreing rapidly within a country.

"We recognise that se measures carry a high ecomic and social cost, so it is important that governments use travel restrictions in a targeted way," said Professor Mark Jit from London School of Hygiene and Tropical Medicine, who led study.

"Before introducing restrictions, y should take into account local infection figures, epidemic growth rates, and volume of travellers arriving from countries heavily-affected by virus," Jit explained.

researchers used detailed flight data to compare number of expected COVID-19 cases arriving from international flights with number of infections arising from transmission within individual countries.

y produced estimates of international travellers in May and September 2020 based on two scenarios.

One scenario used flight data for same months in 2019, assuming reduction in travel numbers, and or scenario was based on expected reduction in passenger numbers.

Numbers of COVID-19 cases and infection rates were estimated using a mamatical model that justs recorded cases to take account of asymptomatic and unreported infections.

Results were determined based on how imported COVID-19 cases would affect local epidemic growth rates, using country-specific reproduction number, or R number estimates.

Where imported cases accounted for more than 10 per cent of infections within individual countries, y were considered to have a major impact on growth of epidemic, study found.

work estimated that when imported cases accounted for less than 10 per cent, ir impact on growth of epidemic is usually small, while those below 1 per cent would have an almost undetectable effect on epidemic size.

researchers ted that h re been travel restrictions or reduction in travel volumes in May 2020, imported COVID-19 cases would account for more than 10 per cent of infections in majority of countries included in analysis, researchers said.

Imported cases would account for more than 10 per cent of infections in 34 out of 136 countries, and less than 1 per cent in four, y said.

According to estimates based on expected passenger numbers in May 2020, imported cases would have contributed to more than 10 per cent of total incidence in 74 countries, less than 10 per cent of total incidence in 62 countries, and to less than 1 per cent in eight countries.

However, by September 2020, h re been travel restrictions or reduction in travel volumes, imported cases would account for more than 10 per cent of infections in only a small number of countries.

Imported cases account for less than 10 per cent of infections in 106 out of 162 countries, and less than 1 per cent in 21, researchers said.

According to estimates based on expected passenger numbers in September 2020, travel restrictions would have contributed to more than 10 per cent of infections in only 37 countries, less than 10 per cent in 125 countries and less than 1 per cent in only 44 countries.

findings indicate that international travel restrictions were most effective at limiting local transmission of virus during earlier sts of pandemic, said researchers, ding this is because imported cases led to outbreaks in countries with very few or existing cases. 

(Im: Pexel/Representative)