Eating out, poor hand hygiene and erratic weather may be among causes, say medics
American Kevin King and Australian Timothy Weeks were kidnapped in August 2016 from outside the American University of Afghanistan in Kabul where both worked as professors.
The US-backed government's decision to carry out the swap is seen as key to securing direct talks with the Islamist militants, who have, until now, refused to engage with what they call an illegitimate "puppet" regime in Kabul.
"The two professors are safely freed and are being taken care of now," said a senior Afghan official on condition of anonymity because he was not authorized to speak to the media.
He did not provide further details.
Earlier on Tuesday, three Taleban sources familiar with the deal, including one in Qatar, home to the political leadership of the Afghan Taleban, said the three Taleban commanders who are part of the swap were freed from jail in Afghanistan.
"Soon after their release, they were flown to Doha and handed over to the political office in Qatar," said a Taleban leader in Afghanistan, who declined to be identified because he is not authorised to speak publicly about the deal.
Spokesmen for the Afghan government and the United States embassy in Kabul were not immediately available for comment.
On November 12, President Ashraf Ghani said Afghanistan would free Anas Haqqani, a senior figure in the eponymous Haqqani network, a militant faction of the Taleban responsible for some of the worst violence in recent years, and two other Taleban commanders.
But the swap was abruptly postponed, with the Taleban then shifting their hostages to a new location.
The Haqqani network has in recent years carried out large-scale attacks on Afghan civilians. It is believed to be based in Pakistan and is part of the Taliban in Afghanistan.
King and Weeks were last seen in a 2017 hostage video looking dishevelled and pleading with their governments to secure their release.
The prisoner exchange could help nudge forward efforts to end the Afghan war.
Pakistan Prime Minister Imran Khan took to Twitter - as news of the release broke - claiming that Pakistan had fully supported and facilitated this release as part of its policy of supporting initiatives for a settlement of the Afghan conflict.
- Imran Khan (@ImranKhanPTI) November 19, 2019
- Imran Khan (@ImranKhanPTI) November 19, 2019
US President Donald Trump halted talks with the Taleban last month, despite his hopes to end America's longest war, following the death of a US soldier and 11 other people in a bomb attack in Kabul.
Before the talks were broken off, the United States and the Taleban both said they were close to reaching a deal.
Eating out, poor hand hygiene and erratic weather may be among causes, say medics
The goal-scoring striker is suffering from a muscle injury sustained during the Champions League quarter-final loss to Real Madrid
Lieutenant General Abdullah Khalifa Al Marri, Commander-in-Chief of Dubai Police, made the announcement on Wednesday
6G will further elevate capabilities of robots, AI, autonomous transport and remote surgery/diagnostics among others
The Nobel laureate has been condemned for partnering with Hillary Clinton, an outspoken supporter of Israel's war against Hamas
Net profit (after tax) up 32% per cent y-o-y to Dh1.45 billion
Goalkeeper Eisa delivered a fantastic performance against Al Hilal to help Al Ain reach the final
Volunteers of the Samantha Kerala Sunni Student Federation used the machine to navigate challenging terrain