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Human metapneumovirus (hMPV) was identified in 2001 as a cause of acute respiratory illness, but its characteristics are still being defined. We analyzed 3740 nasopharyngeal-wash specimens obtained during 2002-2004, using assays for common respiratory viruses and real-time polymerase chain reaction for hMPV. We detected hMPV in 5% of all specimens, compared with 28% for other respiratory viruses. Nucleotide sequence analysis of hMPV isolates revealed the predominant circulation of hMPV genotype A in the 2003 season but a switch to predominantly genotype B in 2004. Sequence analysis also revealed major differences in the hMPV G and SH genes but relative conservation of the F and N genes within each genotype. Phylogenetic analysis indicated a seasonal switch within hMPV genotype A subtypes as well. Despite genetic variability, we found no difference in the severity of illness caused by various hMPV isolates. These findings suggest that hMPV may vary in genetic structure, to allow for a seasonal shift in predominant genotype and the maintenance of infection rates.

Background: Infections with common respiratory tract viruses can cause high mortality, especially in immunocompromised hosts, but the impact of human metapneumovirus (hMPV) in this setting was previously unknown., Methods: We evaluated consecutive bronchoalveolar lavage and bronchial wash fluid samples from 688 patients--72% were immunocompromised and were predominantly lung transplant recipients--for hMPV by use of quantitative real-time polymerase chain reaction (PCR), and positive results were correlated with clinical outcome and results of viral cultures, in situ hybridization, and lung histopathological assessment., Results: Six cases of hMPV infection were identified, and they had a similar frequency and occurred in a similar age range as other paramyxoviral infections. Four of 6 infections occurred in immunocompromised patients. Infection was confirmed by in situ hybridization for the viral nucleocapsid gene. Histopathological assessment of lung tissue samples showed acute and organizing injury, and smudge cell formation was distinct from findings in infections with other paramyxoviruses. Each patient with high titers of hMPV exhibited a complicated clinical course requiring prolonged hospitalization., Conclusions: Our results provide in situ evidence of hMPV infection in humans and suggest that hMPV is a cause of clinically severe lower respiratory tract infection that can be detected during bronchoscopy by use of real-time PCR and routine histopathological assessment.

Cytomegalovirus (CMV) DNA levels were measured by quantitative-competitive polymerase chain reaction (PCR) in weekly leukocyte samples from 50 renal transplant recipients, including 23 with symptomatic and 27 with asymptomatic CMV infection. Peak and week 4 CMV DNA levels were higher in symptomatic subjects (P = .07 and .02, respectively). In a logistic regression model, the logarithm of the week 4 level independently predicted symptomatic infection (odds ratio, 1.78 for a 1 log10 increase; 95% confidence interval, 1.14-2.78; P = .01). All subjects whose week 4 level exceeded 1000 copies/100,000 leukocytes developed symptoms. In subjects with adequate samples for analysis, CMV levels declined exponentially with ganciclovir treatment, with an average half-life of 3.3 days. Levels exceeding 10,000 copies were associated with prolonged time to clearing of CMV DNA. Potential clinical applications of quantitative CMV PCR include predicting occurrence of symptomatic first episodes after transplantation and individualizing duration of antiviral therapy.

A quantitative culture method was used to test serial blood specimens from 28 lung transplant recipients at risk of cytomegalovirus (CMV) infection (donor [D] or recipient [R] seropositive for CMV). Viremia occurred in 26 (93%) of 28 patients. Highest levels were seen when the donor was seropositive. The median of individual maximum levels was 2.13 infectious centers (ICs/10(5) leukocytes for D+/R- patients (interquartile range [iqr], 0.12-21.77), 1.01 for D+/R+ (iqr, 0.3-2.32), and 0.10 for D-/R+ (iqr, 0.07-0.36; P = .030, Kruskal-Wallis test). Higher levels were seen in patients with biopsy-proven CMV pneumonitis compared with those with negative biopsies (mean, 0.24 [SD 0.51] ICs/10(5) leukocytes vs. 0.01 [SD 0.03]; P = .039, Wilcoxon test) and with symptomatic CMV episodes compared with asymptomatic episodes (median, 0.34 ICs/10(5) [iqr, 0.11-0.61] vs. 0.08 ICs/10(5) [iqr, 0.03-0.13]; P = .045, Wilcoxon test). Further studies are required to determine whether quantification of CMV viremia by this method will be of practical value in the recognition of significant CMV infection in lung transplant recipients.

Herpes simplex virus type 2 (HSV-2) is known to cause aseptic meningitis, which can be recurrent. The diagnosis of HSV-2 infection is suggested when meningitis occurs simultaneously with genital lesions but may be obscure if genital lesions are not present or are not appreciated. Viral culture of the CSF is sometimes positive, but it may also be negative, especially in cases of recurrent disease. We report three cases of HSV meningitis in young women who did not have a history of genital herpetic lesions and for whom genital lesions were not noted on presentation. With use of the polymerase chain reaction (PCR), HSV DNA was detected in CSF from all three patients. The diagnosis of HSV meningitis was further confirmed by a positive culture of CSF in one patient's case and by demonstration of intrathecal synthesis of HSV antibodies in a second patient's case. The use of PCR can improve the recognition of HSV meningitis in adults presenting with aseptic meningitis, even in the absence of herpetic lesions.

Results of quantitative shell vial cultures of cell and supernatant fractions of bronchoalveolar lavage (BAL) fluid from lung transplant recipients were compared with results of transbronchial lung biopsies. Cytomegalovirus (CMV) was present in both the cell and supernatant fractions, including 28 (80%) and 29 (83%), respectively, of 35 BAL samples with corresponding biopsies that showed evidence of CMV pneumonitis and 34 (15%) and 75 (33%), respectively, of 227 BAL samples with corresponding biopsies that did not. Cultures of unseparated BAL fluid had a similar yield to cultures of supernatant. Virus titers of cell fractions and supernatants from BAL samples with corresponding biopsies that were positive for CMV pneumonitis were higher than those from BALs with negative corresponding biopsies. Culture of the unseparated fluid is recommended for simplicity and to maximize detection of CMV. Quantitative results may help in the identification of CMV pneumonitis, but additional studies are needed before quantitative cultures can be recommended for routine use.