Traffic on the bridge (left) between Dandong and Sinuiju has noticeably fallen since North Korea imposed its strict measures against Ebola, local businessmen say. (Anna Fifield/The Washington Post)

North Korea has lifted its four-month-long Ebola quarantine, bringing an end to a period of isolation that was notable even by the Hermit Kingdom’s standards.

Embassies and international aid agencies in Pyongyang received a "note verbale" from North Korea's State Emergency Anti-Epidemic Committee informing them that the quarantine was now over for all visitors except for those arriving from a handful of west African countries. Tour operators have also been informed by their North Korean partners and the state airline that the borders are being re-opened.

With no cases of the virus east of Africa, the strictly-enforced 21 day quarantine for everyone entering North Korea — locals and foreigners alike — was puzzling and inevitably sparked theories about what the ban could really be about.

Some speculated it had to do with information control, some with domestic instability and others thought that it actually might be about Ebola. Although the outbreak happened half a planet away and North Korea is not exactly over-run with visitors at the best of times, the country’s medical system is so primitive that one case of Ebola could wipe out a sizeable chunk of the population, observers and traders said. A decade ago, North Korea shut its borders when bird flu broke out in Asia.

In the note sent to diplomats and aid workers "paying gratitude for well keeping the measures taken to prevent the spread of Ebola virus." North Korean authorities said Monday that the quarantine would now apply only to those coming from Guinea, Liberia and Sierra Leone — where the outbreak began — as well those from Guinea Bissau, Senegal, Mali and Cote d'Ivoire.

"Those coming from other countries can work as usual, receiving medical observation through frequent contact with Pyongyang Friendship Hospital for 21 days," said the note, a copy of which was obtained by The Washington Post.

North Korea had been strictly enforcing the quarantine, requiring all foreign residents to remain at home for 21 days after being out of the country and sending a doctor to their apartments each day to take their temperature. Even cleaning staff were not allowed into their homes, and groceries were dropped at the door.

This was a major problem in a repressive country where foreign diplomats and aid workers need regular “sanity breaks,” leaving North Korea regularly to enjoy some outside freedoms. Under the quarantine, working conditions had become so curtailed that some agencies were even considering suspending operations.

Tourism companies have also been told that they can start applying for visas again.

“We have been informed by Air Koryo that North Korea’s borders are now open for travel and the 4-month long Ebola travel ban was lifted as of Monday, March 2,” Uri Tours, one of the companies that takes people to North Korea, posted on its Web site Tuesday. “According to Air Koryo, everything is back to normal! We’re waiting for further confirmation from our tour partners in Pyongyang as to when tours will resume, and what this means for the Pyongyang Marathon.”

The marathon, due to be held in the middle of April, had been closed to foreign competitors because of the ban. The race has historically attracted some competitors from Africa — in 2013, the men’s winner was Ethiopian.

Young Pioneers, another tour operator, said that it had been told that the marathon not take place this year for tourists due to the Ebola restriction, which interfered with preparations for the marathon event. The Arirang mass gymnastics performance has also been cancelled, even though it was not due to be held until August.

Nick Bonner, director of Beijing-based Koryo Tours, said that it had a tour group of about 15 people scheduled to arrive in Pyongyang on March 14.

"We are still waiting for absolute confirmation from our partners that these visas will be issued without any restrictions or caveats, and that the tour will proceed as normal, but all the signs so far are looking good," he said.

"This is not just good news for those tourists interested in visiting one of the world’s most mysterious countries, but also in terms of the work that can now continue in breaking down the barriers and misunderstanding that still exist," he added.

The ban was put in place on October 24 as the Ebola outbreak ravaged three West African countries and a handful of cases occurred abroad. At the beginning, it did not seem to be particularly strictly enforced, but as time went on - and ironically as the outbreak was gotten under control at its source — North Korea applied it to the letter.

As recently as last week, businessmen on the Chinese border with North Korea described the extent to which Pyongyang was going to protect against transmission of the disease. They described quarantine centers and an arduous process by which trucks were sanitized.

The ban was particularly surprising given the effort North Korea has been putting into promoting its tourism industry. It has has set a goal of luring one million tourists to the country, although it has not set a time frame for doing so.

Even those working with North Korea's tourist industry say this number is "aspirational," estimating that the country has 100,000 outside visitors a year. The vast majority are from China.