Advances in Mimivirus pathogenicity.

Viral diseases in the clinical setting have been extensively investigated. Viruses are now considered as potentially responsible for nosocomial infections, especially in intensive care unit (ICU) patients. Mimivirus is the largest virus known to date. Recent studies have suggested that Mimivirus could be responsible for both community-acquired and nosocomial pneumonia. These studies were mainly based on serologic diagnosis, which showed patients with community-acquired pneumonia have more antibodies to Mimivirus than healthy controls. Serologic evidence of Mimivirus pneumonia was also found in mechanically ventilated ICU patients. In a matched-cohort study in which ICU patients with serologic evidence of Mimivirus pneumonia were matched to ICU patients remaining seronegative for Mimivirus, positive serology was associated with an increased duration of both mechanical ventilation and ICU stay. Identification by PCR techniques remains difficult, probably because of the high level of polymorphism of nucleotide sequences of giant viruses. More studies are needed to confirm the clinical impact of Mimivirus in humans.