In the winter-spring seasons 2003-2004 and 2004-2005, 47 (5.7%) patients with acute respiratory infection associated with human coronavirus (hCoV) 229E-, NL63-, and OC43-like strains were identified among 823 (597 immunocompetent and 226 immunocompromised) patients admitted to hospital with acute respiratory syndromes. Viral infections were diagnosed by either immunological (monoclonal antibodies) or molecular (RT-PCR) methods. Each of two sets of primer pairs developed for detection of all CoVs (panCoV) failed to detect 15 of the 53 (28.3%) hCoV strains identified. On the other hand, all hCoV strains could be detected by using type-specific primers targeting genes 1ab and N. The HuH-7 cell line was found to be susceptible to isolation and identification of OC43- and 229E-like strains. Overall, hCoV infection was caused by OC43-like, 229E-like, and NL63-like strains in 25 (53.2%), 10 (21.3%), and 9 (19.1%) patients, respectively. In addition, three patients (6.4%) were infected by untypeable hCoV strains. NL63-like strains were not found to circulate in 2003-2004, and 229E-like strains did not circulate in 2004-2005, while OC43-like strains were detected in both seasons. The monthly distribution reached a peak during January through March. Lower predominated over upper respiratory tract infections in each age group. In addition, hCoV infections interested only immunocompetent infants and young children during the first year of life, while all adults were immunocompromised patients. Coinfections of hCoVs and other respiratory viruses (mostly interesting the first year of life) were observed in 14 of the 47 (29.8%) patients and were associated with severe respiratory syndromes more frequently than hCoV single infections (P = 0.002). In conclusion, the use of multiple primer sets targeting different genes is recommended for diagnosis of all types of hCoV infection. In addition, the detection of still untypeable hCoV strains suggests that the number of hCoVs involved in human pathology might further increase. Finally, hCoVs should be screened routinely for in both infants and immunocompromised patients with acute respiratory infection.

HKU1 hCoV strains circulated in northern Italy during the winter-spring season 2005-2006. Both HKU1 genotypes were detected. HKU1-specific MAb may contribute to the rapid diagnosis of HKU1 infections currently performed by RT-PCR.

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While human rhinoviruses (HRVs) are well accepted as a major cause of common cold syndromes (rhinitis), their role in the etiology of lower respiratory tract infections is still controversial, and their detection in asymptomatic patients is relatively common. The HRV pathogenic role in four groups of hospitalized patients (pediatric immunocompetent and immunocompromised patients, and adult immunocompetent and immunocompromised patients) was investigated by quantifying HRV load in nasopharyngeal aspirates or bronchoalveolar lavage samples by real-time reverse transcription PCR (RT-PCR). Real-time RT-PCR was performed in duplicate on all respiratory samples resulting positive by qualitative RT-PCR. In addition, molecular typing allowed detection of all known HRV species (A, B, and C). In immunocompetent pediatric patients HRVs were mostly associated with lower respiratory tract infections (in the absence of other viral agents) and wheezing, when viral load was > or =10(6) RNA copies/ml. In young immunocompromised patients (stem cell transplantation recipients), an inverse correlation between HRV persistence over time and time at which the infection occurred after transplantation was observed, whereas in adult immunocompromised patients (lung transplant recipients) HRVs could be detected at a medium-low level (<10(5) RNA copies/ml) in bronchoalveolar lavage samples taken routinely from asymptomatic patients. In conclusion, when detected at high viral load, HRVs may cause severe upper and lower respiratory tract infections, whereas when detected at a medium-low viral load, an event more frequent in immunocompromised subjects, they may represent only bystander viruses.