Here is how Trump's travel ban on Europe will work, and exactly who it applies to

• US President Donald Trump has banned travel from 26 other countries for 30 days in a bid to halt the spread of the deadly coronavirus.
• Trump abruptly announced the ban on Wednesday, shocking Europe and the markets, sending airline stocks plunging, and forcing the White House to issue urgent clarifications.
• The ban stops travel from 26 countries, and excludes US citizens and some other groups. It doesn't stop Americans travelling in the other direction to Europe.
• But the ban excludes the UK and Ireland, which have visa-free travel and high levels of movement with those 26 countries, raising doubts about how the ban could work.
• Here's how it works and who it affects.
• Visit Business Insider's homepage for more stories.

President Donald Trump abruptly announced a ban on travel from 26 European countries on Wednesday as he ramped up the US's response to the deadly coronavirus that is spreading across both the European Union and the US.

The announcement caused immediate confusion. European ambassadors were reportedly caught off guard by the plan, and the White House immediately began to walk back and clarify some of the claims Trump made in his announcement speech.

Experts also question why two European countries - the UK and Ireland - were left out of the ban, given that both countries have reported cases and deaths and both have visa-free travel with other countries in the European Union.

Here's how it works and who it affects:

The ban stops people from 26 European countries from flying to the US

The order takes effect from Friday at 1:59 p.m. US Eastern Time (3.59 a.m. GMT on Saturday) and will last for 30 days.

Anyone who is on a flight that took off before this time will still be able to land in the US.

The restrictions apply to most foreign nationals who have been in the 26 countries of the Schengen Area in the 14 days before they plan to arrive in the US.

There are exceptions to the ban, including US citizens

The Department of Homeland Security clarified in a statement after Trump's speech that the travel ban will not apply to United States citizens, most immediate family members of US citizens, or permanent US residents that are currently abroad.

The statement also said that these people are likely to face extra screenings after arriving in the US from these European countries.

The executive order enforcing the ban says that health workers who are helping to stop the virus spread, sea and air crew, people with certain visas, and members of the armed forces are also among those who can get exceptions.

There aren't restrictions on Americans who want to fly to Europe - but it might be a difficult journey

The State Department issued a travel advisory on Wednesday warning Americans to "reconsider travel abroad."

This is the second-most severe advisory it can issue, behind only "do not travel."

There are technically no restrictions on Americans who wish to travel from Europe (aside from the likely increased screenings when they return).

However, the announcement is a major blow to airlines, and many may not offer a full service of flights to Europe if it is not commercially viable to have flights returning in the opposite direction.

These countries make up an area of unrestricted travel, but there are more cases in some countries he hasn't banned

There are 26 countries inside Europe's Schengen Area, which means they have abolished border control and passporting, allowing for a total freedom of movement of people.

In his executive order, Trump said that "the free flow of people between the Schengen Area countries makes the task of managing the spread of the virus difficult."

But experts have questioned the logic of excluding the UK and Ireland from the ban.

The two countries are not part of the Schengen Area but European Union rules around visa-free travel mean that there is still a high level of movement between European countries and the UK and Ireland.

And the UK has reported 456 cases and eight deaths - fewer cases and deaths than the US but higher than many other European countries that Trump has now banned.

Amanda Sloat, senior fellow at American research center Brookings Institution, said: "Trump's 'Europe but not Britain' ban is illogical. UK has more coronavirus cases than some EU states - British Health Minister just tested positive. UK still has open borders with EU. Viruses don't respect borders," The Independent reported.

It is not yet clear if or how the US will stop being travelling from other European countries into Ireland or the UK to get a flight to the US.

More guidance about this is expected in the next few days.

Here's the full list of the 26 countries Trump has restricted travel from:

• Austria
• Belgium
• Czech Republic
• Denmark
• Estonia
• Finland
• France
• Germany
• Greece
• Hungary
• Iceland
• Italy

• Latvia
• Liechtenstein
• Lithuania
• Luxembourg
• Malta
• Netherlands
• Norway
• Poland
• Portugal
• Slovakia
• Slovenia
• Spain
• Sweden
• Switzerland

• Read more about the coronavirus:
• Trump's coronavirus travel ban excludes the countries where he has golf courses struggling for business
• The UK is about to introduce new coronavirus 'population-distancing' measures as hopes of preventing a full epidemic fade
• Coronavirus live updates: Here's everything we know
• The White House scrambles to clarify key details from Trump's speech announcing his coronavirus response

• Read all of our coronavirus coverage here.