To prepare for an April trip to Europe, Sharif El-Mahdi checked the government websites of the United States, his home country and the two destinations on his itinerary. He consulted with his airline, TAP Portugal, and scanned foreign news outlets for information on restrictions and closures. In the days before his departure, he amassed a stack of documents, including coronavirus test results for himself and his young daughter, who needed a nasal swab for Portugal but not Spain. Despite his due diligence, he arrived at Washington Dulles International Airport filled with uncertainty.

“Everything went smoothly, but I wasn’t 100 percent sure I would make it,” said the musician, who owns property in Spain and Portugal. “The rules change on a semiregular basis, and they are sometimes vague.”

The global rollout of vaccinations has emboldened travelers and triggered an avalanche of entry and visitation requirements that vary by country and sometimes by region, province or state. Unfortunately, none of the rules are written in pen, much less stone. Governments are frequently revising them as vaccination rates rise and coronavirus cases fluctuate. Trying to keep up with the latest developments — the European Union may welcome tourists this summer, land borders with Canada and Mexico will remain closed to nonessential travelers through at least May 21, Turkey is under full lockdown — can cause mental whiplash.

“There are a few dozen changes a week as new information is made available about variants, testing and vaccinations,” said Henry Harteveldt, a travel industry analyst with Atmosphere Research. “It all gets uploaded as knowledge becomes available.”

Though we have a wealth of information at our disposal, it can be hard to locate or decipher. Protocols are disseminated like dandelion fluff on a breezy day. Once you track down the regulations, they can be difficult to understand, especially if they were written in the country’s native language or in bureaucratese. To complicate matters, sometimes travel providers offer conflicting advice, even within the same company. I experienced this recently when I helped a Spain-bound friend determine whether she needed her negative test result within 72 hours of departure or arrival — an 11-hour gap, when she factored in her Paris layover. We separately contacted Delta, her airline, and received different answers. An agent told me “arrival,” which Spain’s tourism office confirmed. Yet, Sophie still had to present her test result when she checked in, at the time of departure.

“It is going to be confusing,” Harteveldt said, “but it will get easier.”

For the near future, trip planning will be more challenging — and confounding — than ever. But with the right approach and resources, you can avoid tumbling down the rabbit hole. Evan Jordan, an assistant professor at Indiana University at Bloomington’s School of Public Health who specializes in the intersection of tourism and health, suggests a three-part process. The first step: Is the country open to foreign tourists, and what are the entry requirements?

If you have a specific destination in mind, you can find the pertinent details on the State Department’s covid-19 country-specific information page. (Be aware that the agency recently expanded its “Level 4: Do Not Travel” warning to 80 percent of the world’s nations.) Click on a country — or countries, if you are transiting — and you will arrive at the U.S. Embassy or consulate’s website, which clearly outlines the requirements. Skip down to “Entry and Exit Requirements.” The format is standardized, which simplifies multi-destination searches, and the text is unvarnished.

Aruba: “Are U.S. citizens permitted to enter? Yes.”

Argentina: “Are U.S. citizens permitted to enter? No.”

The State Department collects its information from government agencies, so you don’t have to muddle through other countries’ sometimes byzantine prose. However, if you prefer to go straight to the original source, some ministries and tourism offices have mastered the art of clarity, such as Iceland, Canada and the United Kingdom. And then there’s Italy. (I think Americans fall under List E.)

For a panoramic view of international travel, several industry players have stepped into the arena with user-friendly research tools, such as interactive maps, capsules of information and a time stamp of the last update. The online resources are free and available to anyone — dreamers and doers alike. For instance, the Raleigh-Durham International Airport created a Travel Requirements page that features a color-coded map denoting a country’s level of openness: fully, with restrictions, or closed. Choose your destination and a pop-up box says whether Americans are permitted to visit and displays the prerequisites for entering, such as quarantining, testing and health insurance. To dig a little deeper, the “See More” button addresses such topics as face coverings, local regulations and testing sites. Each category includes links to the primary source, a nod to accountability and transparency.

The North Carolina airport receives its data from Smartvel, a tech company that previously provided events data to the travel industry. The Madrid-based firm, which also works with Delta, United and Iberia, among other airlines, scans 1,000 sources hourly and updates regularly. “The number of changes is dramatic,” said Iñigo Valenzuela, the company’s founder and chief executive. “Some countries can change more than once a day.”

Smartvel pulls its information from government agencies and the International Air Transport Association. The association’s data system, Timatic, relies on more than 1,700 sources and refreshes its content more than 100 times a day, according to an association spokesman. IATA shares its information with paid subscribers but also allows the public to access the interactive map and up to 10 country overviews through its Travel Centre, a page on its website.

“I feel good about what’s out there,” Harteveldt said. “Organizations are keeping up with something that’s evolving quickly.

For the most part, the sites provide similar information in subtly different packaging. A few, however, have broken away from the pack by incorporating bonus features. Sherpa, for one, has a “newly added” and “upcoming changes” section, so you can stay abreast of the most current policy tweaks and prepare for whatever is barreling down the runway. This week’s entries included updates from Bermuda, Bahrain, Iceland and French Polynesia, which announced that it will reopen its borders on May 1. Kayak, the online travel agency, expanded its search filter to include pandemic-related preferences, such as “countries with open borders” and “quarantine not required.” When I chose “countries vaccinated travelers can visit” in Europe, five destinations matched my criteria. Each country profile included the number of active cases per 1,000 people and the percentage of vaccinated residents, statistics vital to the second step in planning: Should you go?

“You need to balance where you can go with where you’ll be safe,” Jordan said.

To assess the health risk, the key factors to weigh are the infection, testing and inoculation rates. The Centers for Disease Control and Prevention created a world map with vaccination figures as well as graphs that allow travelers to compare each destination’s prevention measures and positive case numbers, among other categories. The CDC incorporates data from Johns Hopkins University in Baltimore, the World Health Organization in Geneva and Our World in Data in the United Kingdom, all of which also post their research online. However, for those of us who slept through statistics class, the CDC has grouped the countries by riskiness, from Level 1 (low) to Level 4 (very high), on its Travel Recommendations by Destination page.

A few nongovernmental bodies also provide this information, such as Kayak and Goodwings, which assembled a Covid-19 Travel Guide for Europe for tourists. The Danish sustainable-travel company, which credits the European Centre for Disease Prevention and Control, focuses on regions in the European Union, so you can see the infection rates across the continent as well as within the borders.

The final step is knowing the rules for reentering the States and your home state. All arrivals older than age 2 must present a negative coronavirus test taken no more than three days before departure. Your resident state might also issue recommendations or requirements, such as submitting a health form (New York) or a negative test result for unvaccinated folks (Vermont). But there’s no need to sweat your return. Coming home will be much easier than leaving — at least research-wise.