Diagnosis and epidemiological studies of human metapneumovirus using real-time PCR

Abstract

Background: Human metapneumovirus (hMPV) is prevalent in children, the elderly and immunocompromised individuals, but available epidemiological data is limited.

Objectives: (1) To develop and validate a real-time PCR method for hMPV diagnosis. (2) To determine the percentage of hMPV in respiratory specimens from the community and its association with outbreaks in our geographic area. (3) To provide epidemiological data in terms of age distribution, seasonality and co-infections.

Study design: A real-time PCR assay was designed for detection of hMPV lineages A and B. Prospective testing for hMPV over a 22-month period was then undertaken.

Results: The real-time PCR was sensitive and specific for detection of both lineages of hMPV. hMPV was detected in 9.5% (n=8239) of the specimens and 25% of the outbreaks (n=100) tested. The hMPV-positive patients ranged in age from 18 days to 99 years with a median age of 24 months. The number of positive samples peaked during the winter months of December, January and February. A high rate of co-infections was noted in the samples tested.

Conclusions: hMPV is common in the community and is associated with outbreaks. Including hMPV in routine testing improves etiological diagnosis of acute respiratory infections.

Fig. 1

Limit of detection analysis (probit) hMPV lineages A and B.

Fig. 2

Age range of patients positive for hMPV. Samples for this analysis were collected from January 2005 to March 2006 (inclusive) with n = 8213.

Fig. 3

Seasonality of hMPV. Distribution of positives over the course of the year, percent of respiratory samples tested and the percent positives for hMPV from January 2005 to October 2006 (inclusive) with n = 12,445. Prior to 1 November 2005 only lower respiratory tract specimens were tested for hMPV. After 1 November 2005 DFA-negative NP samples and all other specimen types were tested for hMPV.

Fig. 4

Phylogenetic tree showing the relationship between hMPV viruses based on partial F gene sequence. Reference sequences belonging to lineages A1, A2, B1, and B2 (van den Hoogen et al., 2004a, van den Hoogen et al., 2004b) are given. The length of each pair of branches represents the distance between sequence pairs. The scale below the tree indicates the number of nucleotide substitutions and the units show the number of substitution events. See Section 3.5 for GenBank accession numbers of sequences generated in this study and reference sequences.