Detection and pathogenicity of human metapneumovirus respiratory infection in pediatric Italian patients during a winter--spring season.
BACKGROUND
Some diagnostic, epidemiological and clinical features of the recently discovered human metapneumovirus remain to be investigated.


OBJECTIVE
To study the best approach for the diagnosis of human metapneumovirus infections by both conventional and molecular methods, along with the human metapneumovirus circulation rate in northern Italy and the severity of human metapneumovirus respiratory infections in a pediatric patient population.


METHODS
Nasopharyngeal aspirates (NPA) were taken from 306 pediatric patients during the winter-spring season 2003-2004, and examined for conventional respiratory viruses by direct fluorescent staining and cell culture, while human coronavirus and human metapneumovirus were sought by RT-PCR.


RESULTS
RT-PCR detected human metapneumovirus in 40/306 (13.1%) children positive for respiratory viruses, with an incidence intermediate between that of respiratory syncytial virus (58 patients, 18.9%) and that of influenzavirus infections (29 patients, 9.5%). Phylogenetic analysis showed cocirculation of both human metapneumovirus types (A and B) as well as their relevant subtypes (A1-A2 and B1-B2). Clinically, human metapneumovirus was found to be second to human respiratory syncytial virus alone, as a cause of respiratory tract infections, while duration of virus excretion appeared to correlate with severity of infection, and virus load in NPA with the stage of respiratory infection.


CONCLUSIONS
(i) Human metapneumovirus is a major viral pathogen in the Italian pediatric patient population; (ii) the severity of lower respiratory tract infections approaches that of human respiratory syncytial virus; (iii) there are preliminary indications that the duration of virus excretion may reach 2-3 weeks and that the level of viral load in NPA correlates with the clinical stage of human metapneumovirus infection.
Sarasini
Antonella
A
Servizio di Virologia IRCCS Policlinico San Matteo and University of Pavia, Via Taramelli 5, 27100 Pavia, Italy.
Percivalle
Elena
E
Rovida
Francesca
F
Campanini
Giulia
G
Genini
Emilia
E
Torsellini
Maria
M
Paolucci
Stefania
S
Baldanti
Fausto
F
Marchi
Antonietta
A
Grazia Revello
M
M
Gerna
Giuseppe
G
D000818:Animals; D002460:Cell Line; D002675:Child, Preschool; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007558:Italy / Q000453:epidemiology; D029121:Metapneumovirus / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity*; D009305:Nasopharynx / Q000821:virology; D018184:Paramyxoviridae Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology / Q000821:virology; D010802:Phylogeny; D012141:Respiratory Tract Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology / Q000821:virology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons