Detection and quantification of human metapneumovirus in pediatric specimens by real-time RT-PCR.

BACKGROUND: Human metapneumovirus (h MPV), a recently identified virus, causes respiratory illness in children.

OBJECTIVES: A real-time reverse transcription-polymerase chain reaction (RT-PCR) assay was developed and used to detect and quantify h MPV in respiratory specimens.

STUDY DESIGN: The quantitative RT-PCR assay amplified an approximately 70 base pair fragment from the h MPV fusion protein gene. The assay was validated and used to test respiratory specimens obtained from children seen at a hospital in Seattle, Washington, from December 2002 through May 2003.

RESULTS: The assay detected 1000 h MPV copies/mL of specimen, did not detect 19 other respiratory viruses, and was able to detect and accurately quantify isolates from the four known h MPV genetic lineages in a proficiency panel of 20 previously tested samples. h MPV was detected in 52 (7.2%) of 719 pediatric respiratory specimens. The mean log10 copies/mL of h MPV in the 52 positive specimens was 7.67 (range=4.59-10.60). Children aged 7-12 months had a significantly higher h MPV prevalence (12.4%) than did children younger than 7 months (4.7%) (P<0.005). Children in this age group also had significantly higher levels of h MPV in their respiratory specimens (mean log 8.43 copies/mL) than did the younger children (mean log 6.93 copies/mL) (P=0.0025).

CONCLUSIONS: The rapid real-time RT-PCR assay described here is a sensitive test for clarifying the epidemiology of and diseases associated with h MPV.