013 | Are travel restrictions effective against Covid-19?
In May, I found myself in tears when the British government decided to impose quarantines on anyone returning from France. That was the last straw. How dare they close *my* border? Did it even serve a purpose? When in doubt, go to the library. I turned to science to find out if I had been right to cry or if indeed, the government was doing the right thing. What I found out is... it's complicated.
Sources & further reading
- Delaying the Covid-19 epidemic in Australia: evaluating the effectiveness of international travels bans, Adeshina Adekunle, Michael Meehan, Diana Rojas‐Alvarez, James Trauer and Emma McBryde. Australian and New Zealand Journal of Public Health, 2020 Vol. 44 No. 4.
- Mobility restrictions for the control of epidemics: When do they work?, Baltazar Espinoza, Carlos Castillo-Chavez, Charles Perrings. PLoS ONE 15(7).
- Travel restrictions and infectious disease outbreaks, Ria Vaidya, MSc, Asha Herten-Crabb, MSc, Julia Spencer, MSc, Suerie Moon, PhD, Louis Lillywhite, MSc. Journal of Travel Medicine, Volume 27, Issue 3, April 2020.
- Covid-19 pandemic planning scenarios, US Centers for Disease Control, updated 10 September 2020
- WHO Director-General Dr Tedros address to the 146th Session of the Executive Board, 3 February 2020
- Simulating an epidemic, 3Blue1Brown, 27 March 2020
- Ski, Parti, Seed a Pandemic: The Travel Rules that Let Covid-19 Take Flight, Selam Gebrekidan, Katrin Bennhold, Matt Apuzzo and David D. Kirkpatrick, The New York Times, 30 September 2020.
Music by Dyalla. Additional music by Chris Zabriskie.
Sounds by PiR2, straget, thorvandahl and InspectorJ on freesound.org, under Creative Commons license
Transcripts are published for your convenience, but they are automated and not always cleaned up. Please excuses typos and occasional nonsense, and always check the audio before quoting.
[00:00:00] I don't know that I'm going to use this on the podcast. God, I probably won't because how embarrassing, but I'm in tears. I... Priti Patel just announced quarantine rules for people entering the UK. It's not about popping off to France for a cheeky weekend. For millions of Europeans and of other immigrants , it is about seeing family. For me, it's about going home in July for my dad's birthday. You know, it's just very, very real.
[00:00:47] Isabelle: [00:00:47] I'm going to do some reporting and some interviewing, and God, I hope that someone convinces me that this is justified because then I wouldn't feel so hurt and so targeted.
[00:00:59]Episode intro [00:00:59] Hi, I'm Isabelle Roughol and this is Borderline.
[00:01:14] Today I'm going to fulfil that vow you just heard. That was me back in May being a little dramatic because the government had just decided to impose quarantines on anyone entering England from pretty much everywhere, including France. That made going home impractical, nearing on impossible. And it made the border in the Channel more real than ever for me. And I've been living through Brexit here. And I'll be honest, when this was announced at a time when France had beat back the virus and the situation in the UK was worse, I didn't get it. Worst: I felt targeted. Another easy swipe at immigrants. I realize that didn't age well. In my defense, if you'd been an immigrant in this country the last few years, you too would think that every cabinet decision was made just to spite you. Look, spring was hard, okay?
[00:02:05] Now I cross those 21 miles of saltwater separating me from my family about a dozen times a year. And I can't stress enough how banal that is. French people are the bridge and tunnel crowd of London. There's about 400,000 of us here. Or I should have said how banal that used to be because in 2020, crossing borders is anything but.
[00:02:25] Many countries have opted to close their borders or impose travel restrictions to protect their residents from the coronavirus. A US passport now only lets you into about half the world's countries, with restrictions. Australia, as you heard in a previous episode is a fortress. And getting around Europe has gotten so complex that the EU launched a dedicated website, just to keep up with travel rules in what was supposed to be the Mecca of free movement.
[00:02:51] Maybe that's something we just have to make our peace with for now, if it's actually helping us defeat the pandemic. But is it? That's what I started reading up on at the end of the summer. I had time. I spent two weeks locked in quarantine as payment for a little time on the continent and I wanted answers. Turns out they're hard to find. So here we are in October.
[00:03:12]Before we get started here, two things. First, it's a different kind of episode. You're going to hear more from me, but it's all stuff I learned from my guests. Both of them speak English as a second language and I know many of my listeners do too. If it gets to be too much, remember there are four transcripts on the website, so you can read along. And on the YouTube channel you'll find video versions of the episode with complete subtitles.
[00:03:37] Second and most importantly, a note of caution. Intellectual humility is always a good policy and with anything concerning COVID-19, it is a must. The science is nascent here and there are things that researchers simply don't know yet. We're assembling a puzzle with no clue what the final image is supposed to be. This is the best knowledge that I was able to gather as of this autumn reading what academic literature there is, and speaking to a few scientists. Oh, and also thirdly, stick around because I have to set some things up in the beginning, but then there's stuff that just blows my mind in the second half.
[00:04:14]On mathematicians and models [00:04:14]
[00:04:14] Adeshina Adekunle: [00:04:19] I'm originally from Nigeria. I have a brother and he was supposed to get married in June. And I was planning to go to Nigeria to attend the wedding, but the outbreak started in December and then January, I was already doing my modeling and then I knew I should not travel.
[00:04:40] Isabelle Roughol: [00:04:40] Oh so you knew a lot sooner than us.
[00:04:41]Adeshina Adekunle: [00:04:41] yeah, because that is the benefit of being a mathematician.
[00:04:46]Isabelle Roughol: [00:04:46] Dr Adeshina Adekunle studies infectious diseases of the Australian Institute of Tropical Health and Medicine at James Cook University in Queensland, Australia. He was one of the first to coauthor a study specifically on the issue of travel bans in the context of COVID-19. It was published in May in the Australian and New Zealand Journal of Public Health.
[00:05:07]Adeshina Adekunle: [00:05:07] If my model is telling me that a lot of cases are growing everywhere, I know the travel ban is coming, so I didn't even bother to buy any ticket. My friends, yeah they're like "you mean this thing is going to be serious?," I said, that is what modeling is saying, it's going to be everywhere.
[00:05:27]Isabelle Roughol: [00:05:27] Were people listening?
[00:05:28] Adeshina Adekunle: [00:05:28] I don't think people were listening.
[00:05:31] Isabelle Roughol: [00:05:31] And we know where that got us. A word on mathematicians. Most studies you'll find on the spread of COVID-19 are based on mathematical models. That's both because we haven't had enough time to collect information on COVID yet and because with infectious diseases, field studies are incredibly difficult and ethically fraught to implement. Can you close down a whole country just to see if it works? What's your control group? Would you expose people to a COVID risk for science? So public health experts, mathematicians and social scientists team up to create models that illustrate, but also simplify, human behavior.
[00:06:07]There was a crazy viral video on the 3Blue1Brown YouTube channel back in March that explained quite well how this works.
[00:06:14]3Blue1Brown: [00:06:14] Each simulation represents what's called an SIR model. Meaning the population is broken up into three categories. Those who are susceptible to getting the disease, those who are infectious, and then those who have recovered from the infection. For every unit of time that a susceptible person spends within a certain infection radius of someone with the disease, they'll have some probability of contracting it themselves. Then for each infectious person, after some amount of time they'll recover and no longer be able to spread the disease. Or if they die, they also won't be able to spread it anymore. So as a more generic term, sometimes people consider the R in SIR to stand for removed.
[00:06:54]Isabelle Roughol: [00:06:54] That's the basic principles, though the researchers we're speaking to today, built models far more complex. Complex, but not as much as the real world.
[00:07:02]Baltazar Espinoza: [00:07:02] There is a famous quote saying that all models are incorrect, but some of them are useful.
[00:07:08]Isabelle Roughol: [00:07:08] That's my other guest today, Dr Baltazar Espinoza, also an applied mathematician. He led a fascinating study at Arizona State University this summer that we'll get into in a moment. He's now a post-doctoral research associate at the University of Virginia.
[00:07:23]So that's mathematical models.
[00:07:25]Travel restrictions work but the clock is ticking [00:07:25]
[00:07:25] Now, what are we talking about when we say travel restrictions? Well it's anything that limits contacts between communities and specifically today, I'm just looking at international travel restrictions.
[00:07:39]It can be recommendations like asking people to stick to essential travel only. It can be mandatory quarantines upon returning, which both deter people from traveling and limit their risk of infecting others if they do. That's what we're facing here in the UK. It can be selective travel bans on affected countries as we saw in the beginning of the pandemic, or outright closing of external borders to pretty much everyone, like Australia has done. Travel restrictions essentially reduce contact between the infectious people in our model and susceptible individuals. It's like a quarantine but you're stuck in your country, not your house.
[00:08:16] It's especially effective if you're putting up that restriction between a community with a lot of infectious people -- say Wuhan in February -- and one with a lot of susceptible people -- say everywhere else in February.
[00:08:29] Dr Adekunle's research vindicated Australia's decision to impose an early travel ban on China. Here he is again.
[00:08:36]Adeshina Adekunle: [00:08:36] The travel ban imposed on China was very effective because close to 80% of people who are coming with COVID-19 were prevented from coming in at that time.
[00:08:50] Imposing those travel bans were effective and they are still effective up to now.
[00:08:57] Isabelle Roughol: [00:08:57] Timing is everything. Of course you want to close the barn door before the horses bolt. Or after you've brought them back in. That's another time when travel restrictions are especially meaningful -- when you've controlled the epidemic in your country, and you don't want to reimport the virus from abroad.
[00:09:13] And herein lies the danger: the more successful a country is at beating back COVID-19, the more incentive it has to stay shut down to the outside world. Australia does not expect to open its borders until 2022.
[00:09:26]Doctor Adekunle insists that travel restrictions only buy you time. Time to build hospital capacity. Time to research treatments, time to build a solid test and trace system, time to find a vaccine. And time to help other countries do the same.
[00:09:45] Countries that have succeeded can't just pat themselves on the back and return to life as normal behind their walls. Unless their economy's entirely self-sufficient -- and who is? -- they have a potent self-interest in helping other nations tame the epidemic as well. Because as long as the virus festers uncontrolled somewhere on Earth, none of us can truly open up.
[00:10:08]Patreon appeal [00:10:08]
[00:10:08] Isabelle: [00:10:17] Hey, it's Isabelle. What you're hearing is my most complex work yet on Borderline. The most reporting, the most reading, the most sound design and the most embarrassing personal moments. This is the kind of work you'd normally do in a newsroom, but here we are in the brave new world of journalism. If you want to support this kind of work and everything else I do on Borderline, please become a member on Patreon.
[00:10:40] Isabelle Roughol: [00:10:40] You can name your pledge. Five bucks is great. It helps me cover about 60 quid a month in software and hosting costs for Borderline. And maybe even one day by myself coffee. Members or patrons are ahead of you right now, because they've already listened to this episode. They get it all early and without this annoying bit. They get extra content, behind the scenes and more.
[00:10:59] So join us. Click on 'become a member' at borderlinepod.com or just search for Borderline on Patreon. Thank you. No more interruptions today, I promise.
[00:11:08]The interview that dashes my hopes [00:11:08] I had another scenario in mind. Selfishly: mine. I put it to Dr Espinoza. He uses the phrase "cordon sanitaire". It's French, sorry. It means sanitary cordon, like a ring fence around affected areas. For our purpose it's the same as travel restrictions.
[00:11:28]So what if you have two communities, where the risk is similar and where the infection levels are similar? I'm thinking about between European nations right now, between France and the UK or between Spain and France, you have roughly similar levels of virus circulating right now. Does it make sense to close those borders?
[00:11:49] Baltazar Espinoza: [00:11:49] Yeah, in this case, it makes sense. The 'cordon sanitaire' turns out to be the best strategy actually, for preventing more secondary cases.
[00:11:58]Isabelle Roughol: [00:11:58] Even if they both have the virus circulating a lot already? The thing I'm wondering about is whether, you know, it makes a difference if you're coming to London from Paris , and you're not much more of a risk than if you're coming to London from Manchester, for instance. Does it still reduce the risk then to have that 'cordon sanitaire' at the border, in that case?
[00:12:20]Baltazar Espinoza: [00:12:20] Yes.
[00:12:21] Well, actually there are many
[00:12:22] Isabelle Roughol: [00:12:22] Look, I tried, I really tried, but I was wrong. It is absolutely, epidemiologically justified to reduce my travel across the border. It certainly is now and it was even when the risk was much lower, though it certainly would have been more effective coupled with stricter measures within England. One less infection is still one less infection.
[00:12:43]Dr Espinoza went on to explain that there are other factors like population density and how much two communities usually interact. Remember when I said how banal it is to cross the Channel? Well, ironically for me, that makes it more important to impose those restrictions. That's hundreds of thousands of potentially infectious people you're stopping.
[00:13:02] Ideally, you'd also limit travel between, say Manchester and London, but that's a lot harder, practically and politically. National borders are still the logical place where you can control movement and no, unlike what some on social media might believe, I am not an open border absolutist.
[00:13:21] So let's sum up.
[00:13:23]We've seen how mathematical models work and we've learned that travel restrictions are effective. They're especially helpful for countries with little local virus circulation, but they're also part of the arsenal for countries with high infection rates. Just part. They're pointless. If you don't get your house in order domestically with social distancing, testing, tracing, washing, and wearing masks.
[00:13:45] On the WHO [00:13:45] Tedros Adhanom (WHO): [00:13:45] There is no reason for measures that unnecessarily interfere with international travel and trade. We call on all countries to implement decisions that are evidence-based and consistent.
[00:13:57] Isabelle Roughol: [00:13:58] That was Dr Tedros Adhanom, director-general of the World Health Organization on February 3rd.
[00:14:04]Now, if travel restrictions work, why aren't we closing down every border? Why did the World Health Organization resist them for so long? And why does it now only recommend them half heartedly?
[00:14:15] Well, I'm not going to litigate the rights and wrongs of WHO, but it's worth pointing out that they live in the real-world, not mathematical models. Epidemiologically, sure, locking everything down works. But practically?
[00:14:27] They have to balance other considerations and it's not just big bucks. Will closing borders stop the movement of healthcare professionals and medicine? Will more people die from the resulting hunger and poverty? How long can you keep transnational communities separated without having a massive mental health and human rights crisis on your hands?
[00:14:46]The WHO was also backed up by science, which has shown travel restrictions to be of little effectiveness for most infectious diseases. Sometimes even dangerous, and we'll get back to that. Remember, the science is moving fast here and COVID-19 is sneaky.
[00:15:01]Why asymptomatic covid is even more dangerous [00:15:01]
[00:15:01] When you have the flu, chances are you know, it, and you don't feel like getting on a plane. Also the period during which you may have the flu without symptoms and be contagious is very short. Just one day. So imposing a travel ban against the flu might just stop that one road warrior who refuses to cancel a business trip, even though they feel like crap and they really should know better.
[00:15:29] But with COVID, according to studies, anywhere from 20 to 50% of cases, and it's probably closer to 50, are asymptomatic or presymptomatic. And those people are nearly as infectious as people with symptoms. The American Centers for Disease Control is now working on the assumption that half of all COVID infections happen without the infecting person ever knowing that they were sick or a danger to anyone . That is why, sidenote, wearing a mask to protect others is so important. And that is why stopping people traveling right now might be more important than with other infectious diseases.
[00:16:05] On that plane with just one snivelling road warrior with the flu that everyone's keeping their distance from, there might be dozens of people unknowingly infectious with COVID-19. So wear a mask.
[00:16:17]What happens to the people being locked out [00:16:17]
[00:16:17] Okay. So we now know that travel restrictions work, that they might in fact be extra important for COVID-19 versus other infectious diseases, but also that in the real world, imposing them is not without consequences. They buy you time to get your act together domestically, but they can't be forever. When I say they work, I mean they work from the perspective of the country closing its borders. It is kept safe from secondary infections.
[00:16:46] But what happens outside? What happens to the highly infectious community being told to stay within its own walls? Remember when I said my mind was blown, we're getting to it.
[00:16:56]Let's hear Dr Espinoza explain his research.
[00:16:59]Baltazar Espinoza: [00:16:59] We study the effectiveness of mobility restrictions, assuming that we have two different regions, and the difference is given by socioeconomic features, assuming that in one of them, there is a good access to health services and the other one is a poor region where there is no good access to this type of services. So we may talk about the high- risk community and the low- risk community. And it turns out that there exists a trade off.
[00:17:32] This is counter intuitive. If we allow people moving from the higher risk community to the low risk community, that means that they will be secondary cases in the low risk community. But by exporting these cases from the high risk community to the low risk community, we're expecting that a single infected individual will produce less secondary infection in the safe community than if we left this individual in the high risk.
[00:18:00]Isabelle Roughol: [00:18:00] Okay. Let me rephrase that. Two communities. One rich, one poor. One with good health care, one with poor health care. One with lots of space and fresh air and handwashing facilities, one where people are crammed together, maybe must keep working and can't isolate. These two communities are geographically close together and travel back and forth happens on a daily or weekly basis. Think about the US-Mexico border, a refugee camp on a Greek Island or the slums of any big metropolis in Asia or Africa.
[00:18:34] If people from the poor high-risk community are allowed to continue traveling into the rich low-risk community, they will spread the disease. But they will spread it less than if their community is locked down and they remain all day in cramped quarters with poor health care.
[00:18:49] Baltazar Espinoza: [00:18:49] So by this we are somehow sacrificing some of the individuals from the low risk community, but for the benefit of all, in the sense that people from the higher risk community having access to a better place or to a safer place, the overall final epidemics size will be reduced.
[00:19:11] Isabelle Roughol: [00:19:12] If our goal is to reduce the overall harm of COVID-19 on all of humanity, we shouldn't be imposing travel restrictions on the most vulnerable among us while the virus is present there, or at least not without massive humanitarian help.
[00:19:25]And that means accepting a risk to our own sheltered communities. Good luck selling that plan to any politician or any voter right now.
[00:19:34] But they might see their self-interest.
[00:19:37] Baltazar Espinoza: [00:19:37] In the cordon sanitaire implemented during the 2014 West African ebola outbreak, the infection process was accelerated. It basically created like a bomb in the sense that there were more and more secondary cases and then the cordon sanitaire was released. And then more infected people in the high-risk community actually ended up having contact with susceptible people that were outside of that particular community.
[00:20:05]Isabelle Roughol: [00:20:05] And this teaches us something about our shortsighted world.
[00:20:09] Baltazar Espinoza: [00:20:09] Just in the pure epidemiological context, very pronounced disparities, where there are a rich community that is neighboring a poor community, that represents a high risk for an outbreak. And not only talking about a given outbreak when there is already some infected people, but also talking about these zoonotic events, where a particular disease jumps from animals to human. So these type of disparities actually create systems that promote the expression of, of an outbreak.
[00:20:51]We tend to respond on demand. We tend to look for a vaccine. We tend to look for a treatment or any control measure that will help us after we realized that there is an outbreak. But it is important to start working in creating systems that actually prevents the emergency of these type of events or epidemics. Improving the sanitary conditions of these high-risk regions will help us to reduce the risk of being infected or starting an outbreak in that community, but also that will create a system that is more sustainable over time.
[00:21:33] Isabelle Roughol: [00:21:37] Infectious diseases opportunistic. They find the chinks in our armor, where we are weak and they thrive there. Turns out where we are weakest is not in how connected we are, but how unequal.
[00:21:48]In Europe, as we progress or rather regress towards fuller lockdowns once more, international travel restrictions, aren't front of mind. But they're here to stay and I'm learning to make my peace with it. I have just one request, of our leaders and especially of my friends in media: stop talking about them like they're just an inconvenience for holidaymakers and a loss for the tourism industry. Millions, hundreds of millions in fact, of humans have loved ones on the other side of a border. If it didn't occur to you, get more immigrants in your newsrooms.
[00:22:24] My deepest deepest thanks to Dr Adeshina Adekunle at James Cook University and Dr Baltazar Espinoza from Arizona State University and the University of Virginia, and to the many others whose works I read to understand these issues. Scientists, teachers and librarians are my personal trinity.
[00:22:46] If you enjoyed this episode and learned from it and you enjoy the rest of Borderline, please consider supporting it by becoming a member on Patreon. Members get every episode 24 hours early, they get extra content, extra access, and they help me keep doing this. Go to borderlinepod.com or search for Borderline on Patreon.
[00:23:04]Remember, you can find transcripts, archives, links, everything you need at borderlinepod.com Head there too or in the show notes for the sources for this episode, journal articles, further reading videos and more.
[00:23:16]Music is by Dyalla. Additional music by Chris Zabriskie. Sounds from freesound.org with gratitude to creators, full credits in the show notes.
[00:23:26] And the bit of math explainer is from 3Brown1Blue on YouTube. Check him out, it's addictive in a super nerdy way.
[00:23:33] You can easily find me and chat with me on LinkedIn and Twitter, I'm Isabelle Roughol, Instagram at borderlinepod, and now the YouTube channel where you'll find the episodes as videos with subtitles and sometimes a few extra quirky things.
[00:23:45]Don't forget if you speak French, there's another podcast just for you. It's called La V.F. This week, I'm going to be concluding an epic series ahead of the U S elections, on American institutions and all the quirky things that are completely foreign to most people outside America.
[00:24:02]Just one more week until this huge vote. I think I'm going to do something with live streaming because I'm on lockdown at home and I don't think I can stand election night by myself. Let me know if you're interested.
[00:24:12] Please share Borderline around you and let's grow this community. And don't forget to rate and review on Apple podcasts or your podcasting app of choice, it really helps people find us...
[00:24:21] I'm your host, Isabelle Roughol. Borderline is a One Lane Bridge production. Talk to you next week.
[00:24:28] All right. It's Wednesday morning. I've been home for 14 full days without going out and now I'm allowed outside. So exciting. All right, I've got keys. I've got a mask. Let's go.
[00:24:57] It's a beautiful sunny morning.
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