Human Metapneumovirus Incidence
Human metapneumovirus (hMPV) causes respiratory tract infections in 5-20% of children and adults during winter months, with approximately 5-10% of pediatric hospitalizations for acute respiratory tract infections attributable to hMPV. 1, 2
General Population Incidence
Pediatric Populations
- Overall detection rates range from 5.6% to 12.7% annually in hospitalized children with acute respiratory tract infections, with year-to-year variation 3, 4
- hMPV accounts for 5-10% of hospitalizations among pediatric patients with acute respiratory tract infections globally 2
- Nearly universal infection occurs by age 5 years, with 78.2% of hMPV-positive children being younger than 3 years of age 4, 5
- Primary infection typically occurs during early childhood, though reinfections are frequent throughout life 2
Adult Populations
- Annual infection rates of 1-9% are documented in adults using RT-PCR and serology for diagnosis 5
- hMPV causes 6-12% of exacerbations of chronic obstructive pulmonary disease 5
- Reinfections occur throughout adult life, often presenting with mild upper respiratory symptoms or asymptomatic infection in young adults 5
High-Risk Immunocompromised Populations
Hematopoietic Stem Cell Transplant Recipients
- Symptomatic hMPV infections occur in 2.5-9% of patients during the first 2 years after allogeneic HSCT 1
- Asymptomatic and prolonged viral shedding is common in this population, complicating true incidence estimates 1, 6
- Mortality ranges from 10-30% in HSCT patients who develop lower respiratory tract disease 7
Leukemia Patients
- hMPV is frequently codetected with other pathogens including bacteria, fungi, and other respiratory viruses, obscuring the true attributable burden 1, 7
- Progression to lower respiratory tract disease carries significant mortality risk in this population 1
Seasonal and Geographic Patterns
- Peak activity occurs in late winter to early spring in temperate climates 3, 8, 4
- In tropical regions, circulation peaks in late spring and summer 8
- hMPV demonstrates a stable seasonal rhythm with alternating winter and spring activity, with strong peaks in late spring-summer months every second year 3
- One hMPV subgroup (A1, A2a, A2b, B1, B2) predominates each year and is displaced by another subgroup every 1-3 years 3
- Monthly average temperature negatively correlates with hMPV incidence, with peaks during colder months 4
Clinical Context for Incidence Interpretation
Important caveats when interpreting incidence data:
- Detection methods significantly impact reported incidence rates, with RT-PCR being more sensitive than antigen testing or culture 8
- Coinfection rates are substantial, particularly with RSV, making it difficult to determine hMPV's true attributable morbidity 1, 7
- Asymptomatic shedding rates may be high in immunocompromised populations, leading to potential overestimation of clinically significant disease 1, 6
- The 3-5 day incubation period and high rates of asymptomatic shedding facilitate nosocomial outbreaks, particularly in healthcare settings 6, 2