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.