The New York Times covers the complicated question of whether travel restrictions are good policy in a pandemic. The World Health Organization was strongly against them. Many countries adopted them. They seem to have helped in some places and not others.
Before the pandemic, a few studies had demonstrated that travel restrictions delayed, but did not stop, the spread of SARS, pandemic flu and Ebola. Most, however, were based on mathematical models. No one had collected real-world data. The effect of travel restrictions on the spread of the latest coronavirus is still not understood.
“Anyone who is truthful is going to tell you it’s a big fat ‘We don’t know,’” said Prof. Keiji Fukuda, a former senior World Health Organization official who teaches at the University of Hong Kong.
The U.S. ban on travel from China didn’t work. It turns out it came in time, even though the virus was already inside the country, because those cases petered out. But it was still ineffective. People flew to Vancouver and then entered the U.S. The CDC failed its screening and enforcement role.
The U.S. ban on travel from Europe came too late. It’s the European virus strain that entered New York and largely spread throughout the country. The virus that spread was already here when the ban was put into place.
We never had bans on travel from Iran, Qatar, and any number of other virus hot spots.
The virus has been contained (or at least was contained for awhile) mostly in small, remote countries. The question of why we haven’t seen tremendous spread in places like Thailand, Laos, and Cambodia is a real mystery (their ‘lockdowns’ and public health responses were far from equal, and 90% of Thai cases have been asymptomatic).
Once a virus is in a country and spreading within the community, travel bans don’t offer much protection. The U.S. maintains several bans, including China and Europe, but it’s not clear to what end. Incremental cases brought into the country don’t materially change the direction of spread here.
Keeping a virus out is very hard, ‘viruses are gonna virus’, if you ban passenger travel but still have cargo and the virus spreads via asymptomatic or presymptomatic individuals then cargo crew could bring it in. They could interact with customs or shipping authorities. If a country’s citizens are allowed to return even with quarantine, they could bring the virus in and how perfect is the quarantine? In Melbourne, Australia a quarantined passenger had sex with a guard who contracted the virus and spread it (The Australian state of Victoria practically went ‘full Wuhan’ in its response).
We’ve learned a tremendous amount about this virus in 8 months. The biomedical response has been incredible. But at the beginning we thought fomites and respiratory droplets were the main pathways of spread and aerosols were a non-issue, and that asymptomatic spread was a non-issue as well. Without the knowledge we have today it’s hard to go back and know the right responses then – and whether we could carry out those responses effectively.
The Northeast got the ‘first wave’ of the virus in the U.S. Florida, Texas, Arizona and a few other states were hit with a second wave. Some criticized states for opening up too early, in some sense they may have locked down too early – because there’s only so much lockdown people would stand for and it would have been better to lock down when spread was happening. But there wasn’t much testing at the beginning of the pandemic either and no one knew whether there was spread when lockdowns began.
The issue isn’t just foreign travel either by the way, the virus entered the U.S. but then spread from the Northeast. Perhaps the Europe ban came too late, but domestic travel bans would have worked.
What does it mean to work, though? Would we have been able to contain the virus? Or would we only have been able to delay spread? Delay of course mattered to prepare hospitals in case they faced the sort of overload that hit New York. It helped to give time to build stocks of PPE. And getting the virus later has been better than getting it at the beginning.
Back in February I mused that I might prefer to get it early, on the theory that I’d receive better treatment before hospitals becoming overcrowded. In hindsight I’d certainly have preferred a mild case, followed by perhaps a year of robust immune response (if not long-lasting antibodies) than limiting contacts for so long.
However what waiting has brought is much better patient outcomes – from treatment protocols to antivirals and steroids, it looks like beta interferon will help some patients, and soon we’ll have (an insufficient supply of) monoclonal antibodies as well. It’s better to have a bad Covid case now than back in March or April.
So would travel bans have helped? Could they have been executed effectively? Would they have been worthwhile? My own guess is they can be helpful in theory but they’re really hard to pull off – that at most, for most countries, they can delay spread. And in the case of Covid-19 delay is helpful but that’s not always the case (and it wasn’t something we could have known during the first couple months of the year, because we didn’t know what we didn’t know).
Ultimately the U.S. probably lacks the ability to lock down travel the way some island nations have.