Would the world have returned in March 2020, at the start of the Covid-19 pandemic, when borders were closing one after another? Since South Africa reported the appearance of the new Omicron variant on November 24, the list of nations suspending flights from southern Africa and even other parts of the world has grown. United States, Japan … The World Health Organization (WHO) has calculated (in English) until November 28, “56 countries are said to have implemented travel measures aimed at trying to delay the importation of the new variant”.
WHO warns that “general travel bans will not prevent the spread” of this mutation of the virus which worries the planet. Would this strategy be ineffective? In February 2020, franceinfo devoted an article to this question. Almost two years and five epidemic waves later, has the response changed?
“Two years ago, there was not much in the scientific literature that allowed us to say”, remembers Anne-Claude Crémieux, infectious disease specialist at Saint-Louis hospital, in Paris. The landmark study looked at the influenza virus and was published by UK and US researchers in Nature in 2006 (in English). The conclusion was as follows: “Border restrictions and / or internal travel restrictions are unlikely to delay the spread for more than two to three weeks, unless they are more than 99% effective.”
Since then, new studies specific to Covid-19 have been carried out, most of them based on theoretical models and not observations, pointed out Nature in December 2020. Australian, Scottish and Chinese researchers have attempted to synthesize it in the British Medical Journal end of October (in English). The conclusion of their meta-analysis is mixed. Scientific literature “suggests” While movement controls, quarantines or travel restrictions are “effective measures”, if they are “well respected”. But the authors find that “empirical evidence” are “limited”. First of all, “the number of empirical studies” is “insufficient”. Next, ‘”it is almost impossible to study these strategies as single measures”. It is therefore impossible to draw a formal conclusion on the effectiveness of travel restrictions and border closures alone.
“There was the test of reality”, objected Florence Débarre, researcher in evolutionary biology at the CNRS. At the beginnings of the pandemic, all over the world, the authorities took measures to reduce travel: border closures, local or national confinements, quarantines, curfews … This did not prevent the Alpha variant from appearing. spread globally. Then the Delta variant, more contagious, to supplant it over the months.
“What the first wave showed is that the border closure had a fairly limited impact, when it did.”, judge Anne-Claude Crémieux. An effect which is all the more modest in that“we didn’t have any tests at the time” and so “little knowledge about the evolution of the epidemic” in the population, recalls the infectious disease specialist.
“This pandemic has shown it: the different variants have always arrived here.”
Anne-Claude Crémieux, infectious disease specialistto franceinfo
The role of travel in the global spread of respiratory disease has long been recognized. He “turned out to be central during the first SARS epidemic” from 2002-2003, recall the authors of a study published in Nature in November 2020. Same observation with the Covid-19. “The work showed, quite logically, that the epidemic was reaching countries which had strong international relations”, notes Anne-Claude Crémieux, citing the study published in January 2020 by Inserm (in English).
“Reducing the flow of travelers between countries therefore probably has an action”, deduces the infectious disease specialist. Corn, “given the interconnections and the intensity of international relations, it is almost impossible to completely stop travel between countries, except between very isolated nations”, she notes.
Anne-Claude Crémieux, however, distinguishes “two models”. First scenario: “In ‘zero Covid’ countries or territories [l’Australie, la Nouvelle-Zélande ou la Nouvelle-Calédonie], who associated the closure of borders with other measures (testing, tracing, isolating and breaking the chains of contamination), the measure may have made sense, judge the infectious disease specialist. They protected themselves for a while, as long as they could control the epidemic. ”
Second scenario: “In countries where we are trying to curb the circulation of the virus without preventing it, closing the borders may have saved time, but certainly not blocked the arrival of the virus.”
“What was probably the most useful, without being completely protective, were the sanitary cords in the affected countries, like in China, in Wuhan, believes Anne-Claude Crémieux. It still delayed the arrival of the epidemic in other countries, even if it did not stop it. ” From April 2020, American and Italian researchers measured in Science (in English) this effect (after all limited). The quarantine introduced in Wuhan on January 23, 2020 only delayed the spread of the epidemic by three to five days in China, but international travel restrictions helped slow the spread elsewhere in the world until mid -February”, “by nearly 80%”, they specify.
“It all depends on the state of the epidemic in the affected area”, relieves Florence Débarre. Closing the borders “can be effective, if the epidemic is at its very beginning “. This drastic solution “can make it possible to circumscribe it and to extinguish it“. Corn “If the epidemic has really started in the source area, we need almost sealed borders to limit the travel of infected people”, warns the biologist. However, in fact, “when a virus is detected, it is often already too late, it has already spread”.
The emergence of the Omicron variant confirms this. “Omicron has been detected in southern Africa especially in areas where genomic surveillance is in place, notes Florence Débarre. But given the countries of origin of the travelers that have been detected, it may be more widespread than what we currently have from the genetic sequences shows. “
In addition, in South Africa, where the mutation has been identified, most of the new infections are already linked to it. This not only suggests that the variant has a high potential for spread, but also that it has spread there for some time. Likewise, Omicron was admittedly identified there on November 24, but it was detected in the Netherlands on November 19 and 23, and one of the two people tested had not traveled recently. In other words, the variant had already been circulating for several days thousands of kilometers from its detection zone.
“If it turns out that Omicron is more transmissible than Delta, I don’t see how we can hope to control him, when we already cannot control Delta, any more than we have succeeded in controlling. control Alpha before him. “
Florence Débarre, biologistto franceinfo
Travel restrictions can also have perverse effects. WHO points out that they “may negatively impact global health efforts during a pandemic by discouraging countries from reporting and sharing epidemiological and sequencing data”. A alert also shared, on Twitter, by the leader of the sequencing team in South Africa that enabled the identification of Omicron, Tulio de Oliveira.
The WHO also recalls, as it had already done extensively in the first months of the pandemic, that “Essential international travel – including humanitarian and emergency travel, repatriation and freight transport of essential materials – must remain a priority”.
Even ineffective, closing borders – or at least checks on arrival – remains an option. “We do not know absolutely if it is an alert for nothing or the disaster scenario”, recognizes Anne-Claude Crémieux. Corn “the signs are such that there are reasons to act”, continues Florence Débarre. “In general, in health crises, concludes the infectious disease specialist, it is better to over-react than under-react. ”