Pneumonia caused by Pneumocystis jirovecii (PJP) has substantial morbidity. New risk groups have emerged affecting patients with cancer, organ transplants and other immunosuppression. Case clusters have occurred. 

Clinical risk factors, modes of transmission, and strain variation of the fungus remain uncertain with regard to the genesis of outbreaks, as are strategies to limit infection, including infection control measures and secondary drug prophylaxis, 

In Australia, solid organ transplants appear to be highest risk for PJP outside of HIV/AIDS. Case clusters have been reported many months to years after transplantation, in all renal units along the eastern seaboard (and Adelaide) from 2010-2012 (n=83 cases). Multi-locus sequence analysis of P. jirovecii DNA identified two common major sequence types characteristic of the outbreaks. However, these genotypes are disparate from those causing outbreaks in other countries. Risks for infection include prior CMV infection, underlying lung disease, graft dysfunction and recent anti-rejection treatments. Mortality is 10-30% with graft loss occurring in additional 10-15% of cases. Blanket prophylaxis with cotrimoxazole limited the outbreak in transplant units. Isolation precautions were instituted. 

Contemporary PJP has shifted form one of early infection in high-risk groups to involve cases that occur “late” after initial immunosuppression. Disease is severe and caused by predominant genotype suggesting patient-to-patient transmission. Infection control measures and universal antimicrobial prophylaxis is essential