The CDC. Repeated throughout its “Travel during COVID-19” resource guide is some version of this: “Avoid travel.” (Dreamstime, TNS - TNS/The Minnesota Star Tribune)

Infectious-disease expert Dr. Peter Bornstein understands well the midwinter yearning for palm trees and ocean breezes. Most years, the Twin Cities physician has a family trip booked to a tropical getaway. He's often advised new doctors who've moved to Minnesota from elsewhere to do the same.

This year, Bornstein is checking the powerful urge to buy plane tickets even though he's been vaccinated against COVID-19 as a front-line medical provider. He's alarmed about new viral variants and travel's role in spreading them.

"The concern is that the variants may make 2021 look like 2020," Bornstein said, referring to the past year dominated by disease control measures. "I'd like 2021 to look like 2019."

While air travel and hotel bookings lag far below pre-COVID levels, many of us have nevertheless seen vacation photos posted on social media by friends or family. As COVID-19 metrics in Minnesota trend in the right direction, it's understandable, especially with the recent subzero blast of cold, to want an escape.

Bornstein's advice is to resist temptation. That's also what the U.S. Centers for Disease Control and Prevention (CDC) recommends. Repeated throughout its "Travel during COVID-19" resource guide is some version of this: "Avoid travel."

Note that the agency doesn't distinguish between international and domestic travel. Nor does it make exceptions for those who have been vaccinated or have had COVID. Vaccines, as well as natural immunity after having COVID, may be less effective against new viral variants.

At the same time, the CDC acknowledges that there will be those who venture forth anyway. Its online travel resource covers the recent federal mask requirement on public transportation traveling into or within the United States.

It also spells out another requirement: "All air passengers coming to the United States, including U.S. citizens, are required to have a negative COVID-19 test result or documentation of recovery from COVID-19 before they board a flight to the United States."

From Bornstein's perspective, some critical CDC recommendations haven't received the spotlight they deserve. For example, the agency recommends getting tested for COVID one to three days before departure. The reason: to avoid getting sick with COVID on your trip and spreading the virus to others.

Other key, not-well-understood recommendations involve what to do when you get home. Travelers should get tested again three to five days after their return, and the CDC also recommends quarantining following a trip.

Even if a returning traveler tests negative, the CDC recommends a "full 7 days" quarantine after travel. (You might test negative soon after exposure to the virus). And, "If you don't get tested, stay home and self-quarantine for 10 days after travel." Those who went to last weekend's Super Bowl, for example, wouldn't yet be out of quarantine if they came back on Monday.

An extra step is recommended if there are people in the household who did not go on the same trip. If that's the case, the traveler should "wear a mask and ask everyone in the household to wear masks in shared spaces inside your home for 14 days after travel."

It's the test-and-quarantine information after a trip that Bornstein is concerned that many don't understand. "No one is even talking about that … employers, states, the media. Everybody is kind of focused on the vaccines," he said in an interview with an editorial writer.

Hewing to the recommendation would require travelers to book an extra week or even 10 days out of the office. "I haven't seen people building that buffer in. It's very concerning to me," Bornstein said.

The CDC post-travel guidelines are recommendations, not requirements. A better way to look at them is as a responsibility. It's still best to stay home. But if you must travel, understand and act on your obligations to protect yourself and others.