Experts say travel restrictions the Trump administration put in place to stop the novel coronavirus from spreading could have unintended consequences that undermine that effort.
It's been days since the US restrictions went into effect, blocking foreign nationals who've visited China in the past two weeks from coming to the US.
Details about the US travel ban's impact are still emerging. But some are already urging the US to reconsider.
"All of the evidence we have indicates that travel restrictions and quarantines directed at individual countries are unlikely to keep the virus out of our borders," Jennifer Nuzzo, a senior scholar at the Johns Hopkins Center for Health Security, told lawmakers on Capitol Hill this week. "These measures may exacerbate the epidemic's social and economic tolls. And can make us less safe."
The director-general of the World Health Organization also weighed in this week, calling on countries not to impose travel restrictions.
US officials have defended the government's response, saying they're taking important steps to prepare for the virus and slow its spread -- and that the timing of their efforts is key.
"Hopefully, because of improved global capacity and surveillance and lab capacity, it was caught early, before it spread around the world, and we had this window of time in which they could intervene to slow it down," said Dr. Nancy Messonnier, director of the US Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases.
But several experts who spoke with CNN say there are a number of ways travel bans can backfire when authorities are trying to stop an outbreak. Here's a look at some of them:
Individuals may be more likely to lie
Scientists are still studying how the new coronavirus is transmitted. According to the CDC, it mainly spreads from person to person "via respiratory droplets produced when an infected person coughs or sneezes," like the flu.
With this virus, like others that have come before it, one key tool investigators have as they try to treat it and stop it from spreading is the information individuals share about their symptoms and behavior. And a travel ban can get in the way of that, public health experts say.
"On a personal level, it discourages people from coming forward, from being transparent. You're more likely to have people try and go about travel in less direct ways, which would then totally negate the purpose of that," says Saskia Popescu, an epidemiologist in Arizona and global health security researcher at George Mason University. "You're forcing people into situations that could more actively promote disease transmission."
Governments might also hold back on the truth
The same can be said for how governments could respond once they see travel bans in place, says Dr. Saad B. Omer, director of the Yale Institute for Global Health.
"A lot of this is dependent on voluntary reporting," Omer says.
And governments might be hesitant to share information about novel coronavirus cases in their countries if they feel they'll be punished for doing so.
"If you're the prime minister of a small- to medium-sized economy, there would be a disincentive for you," Omer says. "It becomes a disincentive for international solidarity and collaboration."
There can be major economic consequences
One reason countries may be wary of sharing information: the economic consequences of a travel ban can be devastating.
"It has massive economic implications," Popescu says.
Eric Carter, an associate professor of geography and global health at Macalaster College who studies the politics of public health, points to what happened in West Africa during the Ebola outbreak as an example.
"First of all, it made it harder to some degree for health personnel to get into the country, to actually do the work they needed to do," he says. "Also, it just so severely damaged the economies of those western African countries that were affected by Ebola, because they were cut off from the rest of the world. Other countries weren't even buying what they produced. That ended up having really dramatic effects."
The latest US restrictions could stop hundreds of thousands of people from visiting the United States each month and "come with huge economic and societal impacts," says Sarah Pierce, a policy analyst at the Migration Policy Institute in Washington.
"The way it's written, it seems like it's going to be impossible for Chinese nationals to be granted visas," she told CNN. "This is a massive flow that this ban is restricting with very little evidence that it's actually going to benefit the United States."
'Fear and stigma' can result
World Health Organization Director-General Tedros Adhanom Ghebreyesus warned this week that travel bans might do more harm than good.
"Such restrictions can have the effect of increasing fear and stigma, with little public health benefit," he said Tuesday in Geneva. "Where such measures have been implemented, we urge that they are short in duration, proportionate to the public health risks, and are reconsidered regularly as the situation evolves."
Carter told CNN the past provides plenty of examples of travel restrictions stigmatizing countries and ethnicities. The response to the novel coronavirus, including recent travel restrictions, has happened more quickly than in past epidemics -- and from a public health standpoint, that could be a good thing, he says. But he notes there are also other questions to consider.
"Historically a lot of these border security measures have used public health as a pretext for discrimination. It's very easy to see how a public health rationale would be used to limit immigration for whatever reason," he says. "And I'm not saying that that's actually occurring, but it well could in this particular political climate, not just in the US, but internationally."