Editor's Note — CNN Travel updates this article periodically. It was last updated in its entirety on September 19.
(CNN) — For much of 2021, US passport holders have seen an ever-changing list of international travel options as the world adapted first to vaccines and then to the Delta variant of the coronavirus. Total US cases are around the 42.3 million mark since the pandemic started. Some nations are overwhelmed by Covid cases as well as some US states. In the end, it's up to you to decide whether travel to international destinations is a good idea. The health risks are obvious if you're not fully vaccinated. Nations might change their rules at any time. You may have to adhere to strict curfews and mask mandates. Violations could involve big fines and even jail time. If you want expert input into your decision, the US State Department and the Centers for Disease Control and Prevention provide Covid-19 risk assessments by country. Both agencies rate many of the countries open to US travelers at Level 4, the highest risk for Covid-19. Also, remember that all air passengers 2 and older must show proof of a negative Covid-19 test that's no more than three days old to enter the United States.
List of nations
What follows is a curated, alphabetical list of countries and territories where it's still possible for US passport holders to go for a vacation. Click the links at the end of each destination for important information on:
-- Presenting negative results from Covid-19 tests to enter (including time limits to take the test, types of tests allowed and additional tests upon arrival).
-- Quarantines (if any) and health screenings.
-- Possible exemptions from the rules for the fully vaccinated, people recovered from a recent case of Covid-19 or children.
-- Health insurance requirements, curfews and lockdowns.
-- Different rules if you're arriving from a third country vs. the United States.
These are all things you need to research before you book your trip. People testing positive for Covid-19 upon arrival or while visiting can expect to go into quarantine. Rules for land entry may be different.
This southeastern European country has a gorgeous Adriatic coastline. Testing required; exceptions for the fully vaccinated or with proof of Covid-19 recovery. No quarantine. US Embassy.
Antigua and Barbuda
Stroll along Turners Beach on Antigua's southwest coast.
Scroll down to the Dutch Caribbean entry below for information on Aruba and other islands in this group.
UPDATE: US citizens can now visit this Alpine nation renowned for its culture and food. Testing required to enter unless fully vaccinated or proof of past infection. Quarantine unless fully vaccinated.. US Embassy | Austria Entry Requirements.
UPDATE: Off the coast of Florida, this large chain of islands is loved for its many beaches. Testing required, even for the fully vaccinated. No quarantine in place. Only fully vaccinated may disembark a cruise ship with limited exceptions through at least November 1. US Embassy | Bahamas travel website | Bahamas Travel Health Visa.
Dive Bahrain, an underwater theme park, opened in 2019.
On offer: beaches, interesting architecture and cultural experiences. Testing and quarantine requirements are in place. US Embassy.
English is spoken in this Central American nation filled with wildlife spotting opportunities and stunning barrier reefs. Testing required, even for the fully vaccinated. No quarantine. US Embassy | Belize Tourism Board.
This island in the mid-Atlantic is renowned for its pink beaches and British flair. Testing and quarantine requirements are in place, with stricter rules if you're not fully vaccinated. US Embassy | Bermuda Tourism Authority
A view of Copacabana, a Bolivian tourist town on Lake Titicaca.
Aizar Raldes/AFP/Getty Images
This landlocked South American country offers surreal landscapes from Andean to jungle. Testing and quarantine requirements in place. US Embassy.
Bosnia and Herzegovina
Bosnia and Herzegovina features cosmopolitan Sarajevo and gorgeous lakes. Testing required unless fully vaccinated or recovered from Covid. No quarantine in place. US Embassy | Bosnia Border Police
This southern African nation is famed for its wildlife in the Okavango Delta. Testing required; quarantine is not. US Embassy.
British Virgin Islands
Perched on the Caribbean Sea, Cartagena is a mix of colorful buildings, tropical flavors and a laid-back vibe.
Côte d'Ivoire (Ivory Coast)
Côte d'Ivoire is a popular destination for people wanting to enjoy West African culture and food. Testing required; quarantine encouraged but not required. US Embassy | Travel declaration and fee.
Croatia, the jewel of the Adriatic, is open. Testing required to enter; exemptions for the fully vaccinated or recovered from Covid-19 infection. No standard quarantine in place. US Embassy | Croatia official entry form.
Both parts of this politically divided Mediterranean island are open to US tourists. The Republic of Cyprus and the northern third of the island administered by Turkish Cypriots (Turkish Republic of Northern Cyprus) each have their own rules of entry and testing. US Embassy in Nicosia | Visit Cyprus.
UPDATE: Often at the top of "happiest countries" lists, Denmark accepts fully vaccinated US leisure travelers. No testing or quarantine required. Stricter rules for Greenland and Faroe Islands. US Embassy | Denmark tourist information.
Scroll down to the United Arab Emirates entry below.
Dutch Caribbean islands
Find out the important details on these various Dutch islands in the Caribbean -- renowned for their hospitality and ocean life -- by clicking on the links:
A beach in Oranjestad, Aruba.
LUIS ACOSTA/AFP/Getty Images
Saba: Known more for its rugged landscape and hiking than beaches, little Saba is open. Click on links for latest requirements. Saba Tourism | Saba EHAS application.
This Andean country at the equator also owns the Galápagos Islands in the Pacific. Testing required; fully vaccinated exempted. Quarantine required in some circumstances. US Embassy.
The Nile River nation has been attracting people to see its wonders since antiquity. Testing required; quarantine is not. US Embassy.
Giverny, famed home of Monet, is short train ride from Paris.
JOEL SAGET/AFP/Getty Images
UPDATE: French Polynesia, which includes Tahiti, is the idealized South Pacific destination. Leisure travel allowed only for the fully vaccinated. Testing required; quarantine is not. Islands of Tahiti | FAQ document | Online ETIS form.
French West Indies
NEW: Find out the important details on these various ritzy French islands in the Caribbean by clicking on the links:
Guadeloupe: Open to fully vaccinated vacationers. Testing required; quarantine is not. Guadeloupe Islands
St. Martin: (See Sint Maarten in Dutch Caribbean entry above)
This West African cultural jewel offers historical sites, delicious food and surfing. Testing required. No quarantine. US Embassy.
This Central American country offers historical sites and stunning volcano landscapes. Testing required; exceptions for the fully vaccinated or those fully recovered from Covid-19. No quarantine. US Embassy | Online health pass.
Honduras has epic diving off Roatan Island and other locations. Testing required; fully vaccinated travelers are exempt. Conditional quarantine in some circumstances. US Embassy | Online precheck form.
Great Blasket Island is a hiker's paradise -- and the donkeys seem to like it, too.
Courtesy Tourism Ireland
Home to the amazing ruins of Petra, Dead Sea coastline and the dazzling landscape of the Wadi Rum, Jordan is open to US vacationers. Testing required; quarantine is not. US Embassy | Declaration form | Health form (PDF).
UPDATE: Leisure travel to Latvia is open to only the fully vaccinated. No testing or quarantine required. US Embassy.
This tiny nation is open. Scroll to Switzerland below for details.
US citizens can visit. Testing required to enter; exemptions for fully vaccinated or proof of Covid recovery. No quarantine in place. US Embassy.
People walk along the beach in Cabo San Lucas, Mexico.
The land border between the US and Mexico remains closed through at least September 21, but US travelers can still fly there. No testing or quarantine requirements are in place. The US State Department lists numerous states to avoid because of crime. US Embassy.
US jet-setters can visit the Mediterranean city-state without a test if they are fully vaccinated or recovered from Covid. Otherwise, testing is required. Embassy of Monaco | Principaute de Monaco.
This North African favorite is open to US travelers. Testing required; even the fully vaccinated are suggested to get one. No quarantines in place. US Embassy | Visit Morocco.
US citizens can visit this southern African desert nation that appeals to adventure travelers. Testing required; quarantine is not. US Embassy.
US travelers can visit the landlocked Himalayan nation. Testing required. Quarantine requirements in place, regardless of vaccination status. US Embassy.
The Cathedral of Granada is a popular site.
Home to historical sites such as Granada and tropical beaches, Nicaragua is open. Testing required; quarantines are not. US Embassy | Avianca Airlines.
North Macedonia has a part-Balkan, part-Mediterranean feel. Testing required; exemptions for fully vaccinated or recovered from Covid. US Embassy | TAV Macedonia.
Romania offers mystique, wooded and mountainous landscapes and lots of history. No testing required. Quarantine in place with exceptions. US Embassy | Romanian Embassy.
You can take a fishing trip in Senegal's mangroved-lined creeks and waterways.
UPDATE: Serbia is steeped in historical sites and dramatic Eastern European scenery. Testing is required regardless of vaccination status, but quarantine is not. US Embassy.
This Central European nation of gorgeous lakes is open only to the fully vaccinated or those recovered from Covid-19. No testing or quarantine required. US Embassy | Government of Slovenia
With superb national parks, wineries and the allure of Cape Town, one of the most popular destinations in Africa is open. Testing is required; quarantine is not. Be aware some nations aren't allowing entry to tourists who have recently been to South Africa. US Embassy.
Bibimbap is a popular dish in South Korea.
courtesy Korean Tourism Organization
From busy Seoul to relaxing Jeju Island, South Korea is open. Testing and quarantine requirements are in place. US Embassy | Self-diagnosis app
UPDATE: Sri Lanka is open to US leisure travelers. Testing and quarantine required; shorter isolation if fully vaccinated. US Embassy.
St. Kitts and Nevis
Home of the steep and towering Pitons, waterfalls and volcanic beaches, the independent Caribbean nation of St. Lucia is open. Testing required. Quarantine for nonvaccinated travelers outside Caribbean travel bubble. US Embassy | St. Lucia travel website.
St. Vincent and the Grenadines
Kilimanjaro's glaciers could become a thing of the past as average global temperatures rise.
Sergey Pesterev/Flickr Open/Getty Images/Flickr Open
A favorite for big-game safaris, Indian Ocean beaches and Mount Kilimanjaro, Tanzania is open. Testing required; quarantine is not. US Embassy | Health surveillance form.
UPDATE: Tunisia offers ancient ruins, desert scenery and sunny Mediterranean beaches. Testing required; no exemption for the fully vaccinated. Stricter quarantine for unvaccinated. US Embassy | Online questionnaire.
From cosmopolitan Istanbul to rural coastal escapes, Turkey is open. Testing is required; quarantine is not. US Embassy | Form for entry.
Turks and Caicos
This British overseas territory northeast of Cuba and southeast of the Bahamas is known for coral reefs, ripsaw music and a low-key vibe. All visitors 16 and older must be fully vaccinated to enter. Testing required; quarantine is not. US Embassy | Visit Turks and Caicos | Travel authorization form.
This lush nation in Central Africa offers gorilla trekking, Nile River rafting and beautiful lakes. Testing required; quarantine is not. US Embassy.
United Arab Emirates
The UAE, with its glittering towers and luxury resorts, has emerged as a major world destination in the 21st century. Testing required. Quarantine protocols depend on the emirate. US Embassy.
The Roman Baths in Bath, England.
Matt Cardy/Getty Images Europe/Getty Images
Known for Victoria Falls and wildlife, Zambia is allowing visitors. Testing and quarantine requirements are in place. US Embassy.
Recently removed from the open list
The following countries had been allowing US citizens to enter but have closed again or were removed by CNN Travel for other reasons:
-- Bulgaria. Latest rules make direct visits difficult. US Embassy. -- Cambodia: The US Embassy reports the Southeast Asian nation has stopped issuing tourist visas; you can still apply for business-linked visas. US Embassy. -- Ethiopia: CNN Travel has removed because of ongoing warfare in parts of the country. US Embassy.
This is a curated list and not a full listing. CNN Travel has omitted certain open countries if they had very limited numbers of US travelers before the pandemic; have ongoing or recent armed conflicts, terrorism or rampant crime and unrest; or have entry requirements so extensive and complicated that they put the country out of reach of almost all US citizens. However, you can click here to check for the status and entry requirements of any country or territory in the world you wish to visit.