Ever since a man boarded a flight in Liberia in late September and came down with Ebola in Dallas a few days later, there have been mounting calls to ban flights from Ebola-stricken West Africa. Airport screening systems are not enough, many U.S. senators and others have been saying, adding that the simplest way to keep Ebola out is to stop the infected from getting in.

But public health officials are warning that travel bans would not only be unhelpful and difficult to enforce, they could actually backfire and end up worsening this global health emergency. Here are four reasons why.

Health care aid would be blocked

The World Health Organization has said repeatedly it does not recommend travel bans on the countries affected by the Ebola outbreak because that would leave the countries cut off from the rest of the world, “resulting in detrimental economic consequences, and hinder relief and response efforts, risking further international spread.”

The key problem in travel bans, says the WHO and others, is that ending flights in and out of affected countries hinders these countries’ ability to receive the new supplies they so desperately need. As well, there are already not enough health workers on the ground in the affected countries. What foreign worker would willingly fly into the epidemic to offer assistance knowing they might not be allowed to fly back out?

The U.S. Centers for Disease Control and Prevention Director Thomas Frieden also says cutting off affected countries with travel bans could make the outbreak spread throughout the African continent.

“I'll tell you what could happen very easily if we isolate these countries: harder to get help in, the disease spreads more within these countries, it spreads to other parts of Africa, and within a few months, we're dealing with outbreaks in many parts of Africa,” he told CNN's “New Day” this week.

Could increase fear and panic

In countries where the collective mood has been dominated by fear, mistrust and panic in recent months, travel restrictions could also further anger these countries’ exhausted and frustrated citizens, suggests Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases at the U.S. National Institutes of Health.

“When you start closing off countries like that, there's a real danger of making things worse,” Fauci told "Fox News Sunday” last weekend.

“You isolate them, you can cause unrest in the country. It's conceivable that governments could fall if you isolate them completely. They need help. They need equipment and they need health care workers to come in.”

He then added that “experience is, when you close off a country, you create such stress and fear, you amplify the problem. So, I think any health care person will agree with me that that's not a good idea to completely block off the country,” he added.

Banning travellers isn’t simple

Then there are the practical stumbling blocks.

It’s difficult to imagine how Canada could ban travellers from the affected countries, since no Canadian airline flies directly out of in Liberia, Sierra Leone, or Guinea. Flying from Sierra Leone to Canada means making at least one connecting stop in Europe, or perhaps multiple connections, using one of dozens of airlines.

The patient diagnosed in Dallas, for example, flew from Monrovia to Brussels, then to Washington, D.C., and then on to Dallas. At what point would a travel ban have made sense? And what if new cases start being diagnosed regularly in Europe or the U.S.; would we then have to ban flights from those countries as well?

Some have suggested a compromise, wherein Canada could ban travellers from leaving West Africa but still allow flights into the countries to ensure they get needed supplies. But such a proposal is unlikely to appeal to airlines, which wouldn’t be interested in regularly sending out one-way flights that would return empty.

Travel bans don’t work

Finally, studies have shown that travels bans simply don’t work because they aren’t enough to end all travel in out of the country. Travellers who are unknowingly infected or even those who know they are ill will always find a way to leave.

A study last month used scientific models to predict how this epidemic will grow based on what’s happened so far and barring any changes to end the spread. http://currents.plos.org/outbreaks/article/assessing-the-international-spreading-risk-associated-with-the-2014-west-african-ebola-outbreak/

It concluded, among other things, that even if severe travel bans were put in place that reduced airline traffic by 80 per cent -- which would be difficult in itself -- it would succeed in delaying Ebola’s spread to other countries by only a few weeks. Such a delay would only be useful if the growth of the outbreak could be stopped in that time, which is not likely.

Furthermore, any attempt to isolate the countries would all but guarantee that the epidemic would continue to grow in those countries. And the larger it becomes, the higher the risk that infected patients will make their way out of the countries.

Stepping up screening protocols at airports may help but that is not guaranteed either. The U.S. government promised this week to bring in more thorough questionnaires to better screen arriving airline passengers, following concerns that the Dallas case could happen again. Canadian officials did the same during the 2003 SARS outbreak, but those measures were both ineffective and costly, a study later found.

Not only was more than $7 million spent on that airport screening, not a single new case was detected. The study authors suggested that money would have been better spent on increased screening at hospitals, along with investing in more infection control.

The key to preventing Ebola’s spread to the rest of the world, say most public health officials, is to extinguish the outbreak at its source. Dedicate resources to fighting new infections and ensure that those who need care can receive it without having to leave their country.

Short-term quarantines may have proven helpful at catching some hidden infections, as Sierra Leone’s experience has demonstrated. But worldwide and long-term travel restrictions are another matter and may not be the best approach in the long run.