Long-term study on symptomless human metapneumovirus infection in hematopoietic stem cell transplant recipients.

SUMMARY Human Metapneumovirus (hMPV) is an impor-tant cause of acute respiratory tract disease innormal infants and children worldwide, and alsoplays a role in adults, particularly the elderly andthose with comorbid conditions such as chron-ic obstructive pulmonary disease, asthma andcancer (van den Hoogen et al ., 2002; Williams etal ., 2004; Hamelin et al. , 2005; Williams, 2005;Martinello et al. , 2006). In adult patients withhaematological malignancies and symptomaticrespiratory tract infection, hMPV was recoveredwith a positivity rate of 3-9% (Williams et al. ,2005; Englund et al. , 2006). Clustered cases sug-gesting the possibility of nosocomial epidemicsin hospitalized patients were also reported(Larcher et al. , 2005; Honda et al. , 2006). We recently described a high rate of asympto-matic and persistent hMPV infection in immuno-compromised patients undergoing hematopoieticstem cell transplantation (HSCT) (Debiaggi et al. ,2006). From October 2004 through October 2005,we recovered positive samples from 18 out of 21patients without differences in seasonal distri-bution. In addition, sequence analysis docu-mented infection by hMPV genotype A only andwere identical in the amplified region.This previous observation led us to perform along-term survey to evaluate the real prevalenceof asymptomatic hMPV infection, and the pos-sible appearance of late respiratory sequelae in