Introduction
Human metapneumovirus (HMPV) is a paramyxovirus that causes respiratory tract infections in humans. It was discovered in 2001 in the Netherlands. Infection is most common in winter and spring in temperate climates. This pathogen commonly affects children however adults are affected as well. HMPV is like Respiratory Syncytial Virus (RSV) and has been frequently compared to it. Transmission from person to person is thought to be through nasopharyngeal secretions (1). Incubation period is thought to be five to six days in most cases. Clinical manifestations vary in severity; in the adult population they commonly include cough, nasal congestion, rhinorrhea, dyspnea, hoarseness, wheezing, and fever to a lesser extent. Laboratory studies are generally nonspecific but may include leukocytosis, rise in transaminases or worsening kidney function. Chest radiograph most often is normal (2). The clinical course of HMPV infection is generally mild and may be asymptomatic. Young children and geriatric patients generally are thought to have the most severe clinical manifestations (3). Children have traditionally been studied more extensively since the disease is more common in this population. The increased number and severity of underlying comorbidities may predispose to a worse outcome. HPMV was reported to have a higher prevalence among Human Immunodeficiency Virus infected individuals (4) and leads to devastating illness in patients with hematologic malignancies (5).
HMPV has been demonstrated to affect type 2 alveolar epithelial cells and bronchial cells in Macaques. It has been shown to cause alveolar and interstitial inflammation (6).
Because HMPV tends to occur in the winter and early spring, it may frequently be associated with a coinfection with another virus or bacteria. Dual infections can occur up to 22% (7) and may lead to a more severe disease outcome as well. Up until recently it was difficult to estimate
the prevalence of this infection however with the increasing popularity of multiplex respiratory viral PCR, HMPV is detected much more efficiently.
In this manuscript we will discuss the results of our retrospective study of all adult patients diagnosed with HPMV admitted to our hospital during the year 2017. We will describe the spectrum of clinical manifestations and try to determine the usefulness of the Charlson Comorbidity Index (tool used since 1987 to predict the mortality associated with certain underlying chronic diseases) to predict worse outcome. We hypothesized that similarly to COVID19, infection due to HMPV may be associated with greater morbidity and mortality especially in patients who have a high Charlson Comorbidity Index. Our hospital serves the lower Hudson Valley of New York State.