Low Morbidity but Prolonged Viral Shedding Characterize Parainfluenza Virus 3 Infections in Allogeneic Peripheral Stem Cell Transplant Recipients.

Respiratory viruses including human parainfluenza virus 3 (hPIV3) may be significant causes of morbidity and mortality in patients undergoing allogeneic stem cell transplantation. It has been suggested that the acquisition of hPIV3 infections is independent of immunosuppression or transplant type and is driven primarily by patient exposure to the virus during periods of heightened community-wide or nosocomial activity. The incubation period for hPIV3 is 1–3 days and the duration of infectivity/ viral shedding in non-transplant patients is 1–2 weeks. Data regarding the duration of infectivity/ viral shedding and possible predictors of prolong infectivity in peripheral blood stem cell transplant patients (PBSCT) is limited. Of 56 recipients of sibling PBSCT seen at our insitution, 11 (6 inpatients and 5 outpatients) were positive for hPIV3 during a six weeks period, compared with only two positive cases recorded throughout the previous year. At the time of infection patients were between 1 and 7 weeks post transplant. The in-patient attack rate was 11%. Patients in whom respiratory virus infection was suspected were placed on respiratory isolation and followed with weekly nasopharygeal swab/wash (NPW). Care was also taken to limit patient contact of relatives or staff with respiratory symptoms. Most patients developed a flu like illness without major respiratory complications. No mortality was recorded. No case of hPIV 3 was recorded among patients with aplastic anemia receiving ATG in the unit during the same time-period. The median time to conversion from positive to negative hPIV 3 NPW was 2.0 weeks (range 1–6 weeks). The longest duration of viral shedding (six weeks) was in the only haplo-identical SCT patient, who was also the index case. No differences in duration of viral shedding was noted for conditioning regimen type (ablative vs non-ablative), days after transplant of viral acquisition (<15 or >15 days), cyclosporin levels (100–200 ng/l vs 201–400 ng/l), absolute neutrophil counts, absolute lymphocyte counts, CMV reactivation and co-existing peri-hPIV3 infections evidenced by positive blood, urine or sputum cultures. immunosuppression during the outbreak. Our study demonstrates that while hPIV infection in allogenic PBSCT patients has limited morbidity, prolonged duration of viral shedding in this group may contribute to recurrent cycles of epidemics or prolong outbreaks and establish an environmental (community/ nosocomial) contamination or “ping-pong” transmission from patients to asymptomatic health-care workers or family members and back. Our study also emphasize the importance of a universal policy for strict attention to infection-control practices and weekly surveillance NPW until patients are a symptomatic and NPW negative.