Travel restrictions should be used in a targeted manner to effectively control local COVID-19 infections.

This measure may have limited impact on the epidemic of individual countries, except in countries with low levels of the virus and countries with strong travel relationships with countries with high infection rates.

New studies also suggest that travel restrictions may be effective in countries near turning points. Exponential growth-Plays or Rs are between 0.95 and 1.05-but not what it is already rapidly spreading among the population.

By late April 2020, all countries in the world had imposed some form of travel restrictions with high economic and social costs as part of their efforts to curb the spread of COVID-19. However, to date, no studies have produced global estimates of how the risk of importing cases is associated with local levels of infection. The results of this study will allow policy makers to determine where travel restrictions have a significant impact on delaying infections in the area and where they have little impact.

“We recognize that these measures are economically and socially costly, so the government has imposed travel restrictions,” said Mark Jit, a professor at the London School of Economics and Tropical Medicine, who led the study. It’s important to use it in a targeted manner. Locals should be taken into account before introducing restrictions. infection Numbers, epidemic growth rates, and the number of travelers arriving from countries strongly affected by the virus. “

The authors used detailed flight data to compare the expected number of COVID-19 cases arriving from. International flights The number of infections resulting from infections in individual countries (assuming no travel restrictions). The author created estimates for overseas travelers in May and September 2020 based on two scenarios. One scenario used flight data for the same month of 2019 (assuming no decrease in travel), and the other scenario was based on the expected decrease in passenger numbers. The number of cases and infection rate of COVID-19 were estimated using a mathematical model that adjusted the recorded cases and considered asymptomatic and unreported infections. Results were determined in a country-specific manner based on how imported COVID-19 cases affect the growth rate of epidemics in the region. R number estimation.When imported cases account for more than 10% of infections Individual countries, They were thought to have a significant impact on epidemic growth. The study estimates that less than 10% of imported cases usually have a small effect on epidemic spread, and less than 1% of cases have a negligible effect on epidemic scale. We used publicly available country-specific estimates of R numbers to identify countries near the turning point of exponential growth (R numbers between 0.95 and 1.05).

If there were no travel restrictions or reductions in travel volume in May 2020, imported COVID-19 cases would account for more than 10% of infections in the majority of countries (102/136 countries included in the analysis). Let’s do it. Imported cases will account for less than 10% of infections in 34 of 136 countries and less than 1% in 4 countries. Estimates based on projected passenger numbers in May 2020 show that imported cases contributed more than 10% of total incidence in 74 countries, less than 10% of total incidence in 62 countries, and less than 1% in 8 countries. It is thought that you are doing it. ..

However, by September 2020, if there were no travel restrictions or reduced travel volumes, imported cases would account for more than 10% of infections in very few countries (56/162 countries). I will. Imported cases account for less than 10% of infections in 106 of 162 countries and less than 1% in 21 countries. Estimates based on the estimated number of passengers in September 2020 suggest that travel restrictions contribute to more than 10% of infections. Less than 10% in only 37 countries, 125 countries and less than 1% in only 44 countries (see appendix for country-level data).

In September 2020, passengers are expected to decline, and out of 44 countries where imported cases account for less than 1% of regional infections, 22 countries have estimated R numbers above the turning point (ie R1.05). This means lifting the trip. Restrictions in these countries are unlikely to cause regional outbreaks (see appendix for country-level data). In May 2020, passengers are expected to decline, and only five countries have estimates of cross-turning R numbers, with imported cases expected to account for less than 1% of regional infections. is.

The findings show that international travel restrictions were the most effective in limiting local transmission of the virus in the early stages of a pandemic. This is because imported cases occurred in countries with few or no cases.

The authors conclude that the recommendations on international travel restrictions should not be applied uniformly. Countries must first consider the number of infections and epidemics in the region, and the number of travelers arriving from countries that are heavily affected by COVID-19. For example, in September 2020, the virus was suppressed to very low levels in New Zealand and China, and the expected number of imported cases would be the same as the local proportion, so countermeasures would be effective. Local wave of infection.

The estimates produced in this study assume that the COVID-19 rate of international travelers is the same as the general population of the country of origin. However, people with symptoms in the first place are less likely to travel and may be found by regular screening, which can reduce the rate of arrival of an infected person. People during the incubation period while traveling may develop symptoms and be discovered or self-report their illness when they arrive at their destination.This is because the number of imported COVID-19 cases is Travel restrictions It is overrated in this study.

The authors also evaluated only international flight data. In short, their analysis may not be able to accurately determine the risk of COVID-19 spreading between countries with heavy land traffic (such as railroads and roads). Travel Between the countries of continental Europe).