Serosurvey of human metapneumovirus infection in Croatia

Aim

To assess the seroprevalence of human metapneumovirus (hMPV) in Croatia.

Methods

During 2005, a total of 137 serum specimens from Croatian patients aged from 6 days to 51 years, without respiratory symptoms, were collected at the Croatian National Institute of Public Health. The sera were examined using the indirect immunofluorescent assay.

Results

The overall hMPV seropositivity rate in the samples tested was 77.4% (106/137). The seropositivity rate increased from 18.7% in children aged between 6 months and 1 year to 100% in people older than 20 years of age. The highest proportion of titers ≥1:512 was found in children aged from 1 to 2 years.

Conclusion

Our results suggest that hMPV infection is present in Croatia, with primary infection occurring in early childhood. This is the first study that indicates the circulation of hMPV in Croatia.Human metapneumovirus (hMPV) is a newly discovered respiratory virus assigned to the Paramyxoviridae family, Pneumovirinae subfamily, Metapneumovirus genus. It was first isolated in 2001 from nasopharyngeal aspirates obtained from young children in the Netherlands (1). Sequence analysis of several isolates identified two major genetic lineages (subtypes A and B) that can be further divided into subgroups A1, A2, B1, and B2 (2). HMPV causes acute respiratory tract infections in all age groups (3,4). In hospitalized young children, hMPV infection is commonly present as bronchiolitis with or without pneumonitis (5,6), whereas bronchitis, bronchospasm, and pneumonitis are most commonly seen in elderly patients (3). Since the initial report, hMPV has been studied all over the world and it has been reported on all continents (7). Seroprevalence surveys from the Netherlands (1), Japan (8), and Israel (9) indicated that virtually all children are infected by 5-10 years of age. The aim of this study was to demonstrate the presence of hMPV infection in Croatia, by examining sera from Croatian people for specific anti-hMPV antibodies by an indirect immunofluorescent assay (IFA).