Traveling (or Returning) to the U.S.? Prepare to Take a Coronavirus Test

According to a C.D.C. order, airlines must comply with these rules to receive permission to disembark passengers in the United States.

What kind of tests are required?

The C.D.C. stipulates that negative results need to come out of a test that can detect an ongoing infection, by picking up on pieces of the pathogen itself. Two types of tests fall into this category: molecular tests (which include P.C.R. tests) and antigen tests. (Antibody tests, which can only determine whether someone was infected in the past, don’t count.)

Molecular tests search for segments of the virus’s genetic material, or RNA. The most common molecular tests rely on a tried-and-true technique called polymerase chain reaction, or P.C.R. — a gold standard in infectious disease diagnostics. P.C.R. tests can carry a hefty price tag, and, because they require samples to be routed through laboratories, they might take a few days to return results. Experts say it’s a good idea to plan ahead if you opt for this type of test.

There are a couple of rapid molecular tests that can run from start to finish in a doctor’s office in a matter of minutes. These include Abbott’s ID Now test. They’re considered less accurate than P.C.R.-based tests, but will get you answers faster.

Antigen tests hunt for pieces of coronavirus proteins, or antigens. They tend to be less accurate than molecular tests, and are worse at finding the virus when it’s scarce. But most antigen tests can be done very quickly and cheaply, taking only minutes to deliver results.

Certain antigen tests are cleared only for use for people with symptoms, and might more frequently deliver inaccurate results when used to screen people who feel healthy.

Depending on the country that travelers are departing from, certain tests might not be available — and, as a result, these new rules will likely make it a lot harder for people to enter the United States. Tests are generally offered through health care providers or community testing sites, which can be located via tourism bureaus and local health care providers. Some airports, such as Heathrow in London, are offering on-site coronavirus testing. And a few airlines, like American, Jet Blue and United, are offering to help their customers in certain countries arrange testing. Delta, for instance, has partnered with Mayo Clinic and national health authorities in multiple countries to ease the test-and-travel process.