This is an important story, if you haven’t been following it. Five nurses and one doctor working in a Libyan hospital have been accused of intentionally infecting hundreds of children with HIV in 1998. Detained since 1999, they were convicted and sentenced to death in 2004, but the Libyan Supreme Court threw out the results and ordered a new trial. Today, the verdict was returned from that trial: death, again. The problem is, Libyan courts are ignoring the scientific evidence that supports the workers’ claims of innocence. A couple different analyses have been performed exonerating them. The first is described by Nature here:

During the first trial, the Libyan government did ask Luc Montagnier, whose group at the Pasteur Institute in Paris discovered HIV, and Vittorio Colizzi, an AIDS researcher at Rome’s Tor Vergata University, to examine the scientific evidence. The researchers carried out a genetic analysis of viruses from the infected children, and concluded that many of them were infected long before the medics set foot in Libya in March 1998. Many of the children were also infected with hepatitis B and C, suggesting that the infections were spread by poor hospital hygiene. The infections were caused by subtypes of A/G HIV-1 — a recombinant strain common in central and west Africa, known to be highly infectious.

But the court threw out the report, arguing that an investigation by Libyan doctors had reached the opposite conclusion. Montagnier believes the judgement was based at least partly on mistranslation from English to Arabic of the term ‘recombinant’ — instead of referring to natural recombination of wild viruses, as intended, it was interpreted to mean genetically modified, implying human manipulation.

Earlier this month Nature published another analysis, concluding the same thing:

In 1998, outbreaks of human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) infection were reported in children attending Al-Fateh Hospital in Benghazi, Libya. Here we use molecular phylogenetic techniques to analyse new virus sequences from these outbreaks. We find that the HIV-1 and HCV strains were already circulating and prevalent in this hospital and its environs before the arrival in March 1998 of the foreign medical staff (five Bulgarian nurses and a Palestinian doctor) who stand accused of transmitting the HIV strain to the children.

The degree of certainty of the results is pretty high, according to the authors of that paper:

We found that, irrespective of which model was used, the estimated date of the most common recent ancestor for each cluster pre-dated March 1998, sometimes by many years. In most analyses, the probability that the clusters from the Al-Fateh Hospital originated after that time was almost zero. For the three HCV clusters, the percentage of lineages already present before March 1998 was about 70%; the equivalent percentage for the HIV-1 cluster was estimated at about 40%.

The basic idea behind the science is pretty straightforward: viruses mutate at a high rate. By gathering the available samples of the HIV strains present in those infected at the hospital molecular biologists can compare them and come up with a common ancestor. The time it would take for the current strain to evolve, given the number of mutations separating the common ancestor from the current strains, can then be estimated, using different models of mutation rates. As the authors point out, using several different models gave them the same result: the strains they studied had a common ancestor that appeared prior to March of 1998. That means the transmission of the virus had started before the workers arrived at the hospital.

They have one more appeal under Libyan law. There’s a list of things you can do to help out over here.