Americans are currently barred from traveling to Europe, but that does not mean they have no option for a great summer vacation. There are plenty of countries, especially in the Caribbean, welcoming Americans with open arms — as long as they provide local authorities with the negative result of COVID-19 test.

Antigua, St. Lucia, Jamaica, the Bahamas, and many other nations require that travelers show proof of a negative COVID-19 test prior to arrival, but rules vary widely from country to country, creating confusion among the traveling community and inserting doubts in tourists’ minds about the usefulness and effectiveness of the tests. To better understand if COVID-19 tests are truly the ultimate green light for traveling, what tests work best, and if tests are as effective as isolations, we asked expedition and wilderness medicine specialist Dr. Andrew Peacock to give us the lowdown on COVID-19 tests.

Dr. Andrew Peacock has been practicing medicine for 20 years. He works as an emergency doctor in Australia, as a wilderness and expedition medicine doctor, and also as a photography instructor for Lindblad Expeditions. His focus when working on guided trips in India, as a ship doctor on expeditions to Antarctica, or leading treks in Nepal is prevention and risk reduction, so he is acutely aware of what COVID-19 tests can and cannot do for the traveling community and the tourism industry.

Q. Are COVID-19 tests 100 percent accurate and reliable?

A. It is possible for someone who has been infected one or two days prior to being tested to be asymptomatic and to test negative. That’s because the virus would not have had quite enough time to multiply in their nasal passages for it to be detected during a test, so those people can subsequently become infectious. That short window of time when the virus is not detectable is not precisely known.

A false-positive result, i.e. a positive test result even though the person tested is not infected by the virus, can also happen, even if they are very rare. The same goes for false-negative results. No tests are ever 100 percent accurate.

Q. Most nations that require proof of a negative COVID-19 test ask for RT-PCR tests. What are they? What types of tests are best?

A. RT-PCR tests are conducted through nose and throat swabs that detect the viral particles in mucosal secretions. They are the most accurate and most common forms of testing to detect current COVID-19 infections.

PCR saliva tests without swabs are also used in some cases, but although they present advantages, they are less sensitive than nose and throat swabs.

Blood tests are conducted to detect antibodies, i.e. to know if you have had the virus. A blood test is not the best way to decide if someone is currently infected with the virus, but it can be useful to indicate past infections. Note that we do not yet know with 100 percent certainty if a person who has been infected with COVID-19 in the past can’t get sick again, so COVID-19 blood tests are not a free pass for people to stop taking health measures seriously.

Q. Can COVID-19 tests replace 14 days in isolation?

A. Putting people in isolation for 14 days is the best thing to do to prevent the spread of the virus because testing does not pick every infected person up, but it’s obviously not conducive to a thriving tourism industry.

Q. Why are there so many different rules around testing for COVID-19 around the world? Some countries require that you take a test 72 hours prior to arrival, others ask for seven or 10 days prior to arrival, and some nations only make travelers take a test once they have landed. Why are there such disparities between nations?

A. Every country’s chief epidemiologist or chief medical officer has a slightly different point of view as to when is the best time for incoming people to take a COVID-19 test to ensure that they are not infected with the new coronavirus. Nobody knows exactly how to pinpoint the best time for someone to take a test prior to traveling, because it depends on many factors that are out of the hands of destinations. Add to this the fact that there are logistical constraints associated with testing, reading results, paperwork, and you have a disparity of rules and regulations throughout the world. It’d be great if there was a worldwide consensus on testing, such as “take a test two days before arrival,” but we’re not there yet.

All of these attempts by the various jurisdictions, countries, or states are the best guess estimates as to how they can capture the greatest percentage of infectious people as possible before they travel. They’re looking to reduce the risk to zero as much as possible knowing that with a negative test result prior to arrival, the chance of having infected people coming in is very low, even after spending several hours in a packed plane.

Q. Isn’t it possible that people get infected in the airplane on their way to a destination?

A. If everyone on the plane had to produce a negative test prior to arriving at a destination, then there’s very little chance of anyone being infected in the airplane since all the passengers should theoretically be COVID-19 free. Also, although there’s almost no social distancing possible aboard a plane, people are required to wear masks, the aircraft are fitted with high-quality air filters, and everything is thoroughly cleaned, making airplanes as safe as they can be.

Q. As of August 1, 2020, Sri Lanka will reopen to international tourism, but the country requires four COVID-19 tests throughout the duration of your stay. The first should be taken within 72 hours of your departure to Sri Lanka, and the second administered at the airport, free of charge, though you will have to isolate for 24 hours while waiting for the results. The third test must be taken four to five days after your arrival, and if you’re staying for 10 or more days, you’ll have to take yet another test on the 10th day. If you test positive at any point, you will be required to quarantine for 14 to 21 days. What do you think of Sri Lanka’s testing procedures for incoming travelers? Is it the way to go to make sure the spread of COVID-19 stays under control while keeping tourism going?

A. By doing that Sri Lanka is as close as possible to reducing the risk of travelers spreading the virus to zero. They are trying to catch just about every person who may have slipped through the net and protect their country, but why would anyone want to go to Sri Lanka in those conditions unless they had no choice? And considering that there’s a possibility, even if small, of taking a test and getting a false positive, that would then require in-country quarantine or an immediate return home, traveling to Sri Lanka seems to be risky for travelers.