One of the major elements preventing the transmission of pathogens from animals to humans is the species barrier. We have known for a long time that apes are the closest relatives of humans, with 99% genomic similarity. It is therefore not surprising that the same pathogens can affect us. Over the past few years, pathogens that were thought to be strictly human have been shown to have actually first developed in apes, especially the human immunodeficiency virus (HIV), as reported by Delaporte , and the paradigm of malaria, as reviewed by Duval and Ariey  and Calvignac-Spencer et al. . For these two cases, it seems that apes constituted the initial reservoir and the source of our infections. It is clear that eradicating those infections, including malaria, could not be achieved without attempting to do this also among apes, which seems unfeasible with regard to wild apes. Moreover, the apes are also sensitive to the same pathogens as we are, especially the Ebola virus, which has its origin in bats, and has caused great damage among apes. Finally, many bacteria and parasites, including Streptococcus pneumoniae, Necator americanus, and Bacillus anthracis, may affect the great apes just as they affect us.
A breakthrough has been achieved over the last few years, by the use of ape faeces, and, in particular, access to wild gorilla faeces. Surprisingly, these studies have shown that traces of HIV and Plasmodium can be found in gorillas faeces, even though faecal matters were never used in this regard.
Meanwhile, a debate is currently under way in the USA , about whether we should continue to use chimpanzees, which are, of course, the closest experimental model to humans, in scientific experiments; this is a complex ethical debate, on which opinions diverge. Today, non-invasive methods have also been shown to be useful in documenting the natural history and pathogenicity of simian immunodeficiency virus (Siv) infection in wild chimpanzee populations.
This special issue has two important features that I believe are important for the infectious diseases and clinical microbiology medical community: first, the very unusual use of faeces for the diagnosis of systemic diseases, and in particular the diagnosis of malaria; and second, the role played by apes in the epidemiology of human diseases. As the majority of emerging infectious diseases have their origin in wildlife, extending the use of faecal samples to study other pathogens in wildlife could significantly increase our knowledge of the origin of other infections and help to identify reservoirs.