Research has always suggested that the infected children contracted HIV because of poor hygiene and sterilisation practices at al-Fateh hospital which predated the arrival of the health workers in Libya.

The case against the “Benghazi Six” was further weakened by a study published this month. A team led by Tulio de Oliveira of Oxford University used samples of HIV taken from infected children being treated in Europe to trace the genetic history of the viral subtype in their bodies.

As genetic mutations accumulate at a fixed rate, this can provide an accurate timescale for the outbreak, and the results showed that the HIV subtype was already infecting patients long before March 1998, when the accused staff arrived.

Oliver Pybus, a member of the Oxford team, said yesterday: “There are just too many genetic differences between the infections for them to have all occurred since the arrival of the foreign medical staff — it’s that clear.”

Further evidence that supports the medical workers has been compiled by Professor Luc Montagnier of the Pasteur Institute in Paris — who discovered HIV — and Vittorio Colizzi, of Tor Vergata University in Rome.

Their analysis of practices at al-Fateh hospital concluded that the outbreak probably began in April 1997 with a single child who was already infected with a sub-Saharan strain of HIV when admitted.

The virus then spread to other children because needles, catheters and other medical devices were not properly sterilised.

Many of the patients were also infected with hepatitis C, which is transmitted in the same way as HIV, pointing further towards poor hygiene as the likely origin of the outbreak.

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