Assange, the founder of the whistleblower site WikiLeaks, is currently in British custody at a top-security Belmarsh jail. In February next year he is to stand trial over an extradition request from the US, where he may be sentenced to up to 175 years in prison. In an open letter addressed to British Home Secretary Priti Patel, over 60 medical professionals from across the world voiced their concern over the physical and mental health of the publisher, arguing that he may not only be unfit to stand a trial but even at risk of dying.

“We have real concerns, on the evidence currently available, that Mr Assange could die in prison. The medical situation is thereby urgent. There is no time to lose,” the letter says.

The doctors cite several eyewitness accounts demonstrating deterioration of Assange’s health during his seven-year-long say at the Ecuadoran embassy in London. The Australian-born anti-secrecy activist breached his bail conditions by hiding at the diplomatic mission in 2012 and remained there until his eviction in April this year.

A UN panel of experts concluded that the self-exile amounts to his arbitrary detention by the British authorities, considering the circumstances.

A threat of arrest made it impossible for Assange to get treatment at a proper hospital over that period of time, even as living in confined conditions and increasing isolation took their toll on his health. The medics that did get a chance to examine him at the embassy did so against the background of a “climate of fear and intimidation”, the letter said, which was most likely created deliberately.

The concerns were further fueled by the opinion of Nils Melzer, the United Nations special rapporteur on torture, who visited Assange in prison in early May, accompanied by two medical experts specializing in assessing victims of torture. He said the team concluded that Assange had symptoms of a person who sustained psychological torture over an extended period of time.

Assange’s latest public appearance during a court hearing last month further demonstrated his ailing health. The man seemed exhausted and confused, struggled to recall his own name and date of birth and complained that he couldn’t think properly.

The signatories called for an urgent expert medical assessment of Assange’s state of health that should be done “in a properly equipped and expertly staffed university teaching hospital,” as opposed to the prison’s hospital ward.

US accusations of Assange filed under the Espionage Act stem from WikiLeaks publishing of classified materials embarrassing to the US government. Supporters see his mistreatment as a major attack on freedom of speech with disastrous consequences for whistleblowers and journalists, who consider exposing wrongdoing by Western governments.

The open letter was signed by medics from the United States, Australia, Britain, Sweden, Italy, Germany, Sri Lanka and Poland.