Introduction
Human Metapneumovirus (HMPV), identified in 2001, belongs to the Metapneumovirus genus of the Paramyxoviridae family. It is a major cause of respiratory illnesses across all age groups but poses particular risks to infants, the elderly, and immunocompromised individuals.
Although HMPV shares similarities with respiratory syncytial virus (RSV) and other respiratory pathogens, it remains underdiagnosed, with a significant gap in understanding regarding its full clinical impact. This review aims to provide a detailed overview of the virus's clinical manifestations, epidemiology, diagnostic strategies, and current management approaches [1].
Epidemiology
HMPV infections predominantly occur in the colder months, exhibiting a seasonal pattern akin to RSV and influenza [2]. Global studies indicate that HMPV can affect individuals of all ages, though it causes the most severe illnesses in the very young, elderly, and those with compromised immune systems [3].
Epidemiological data suggest that by age 5, nearly all children will have experienced an HMPV infection, although most cases are mild or asymptomatic [4]. In hospital settings, HMPV has been detected in 3-15% of patients with respiratory tract infections, with variable prevalence across different regions [5].
Clinical Features
In immunocompetent individuals, HMPV typically causes mild upper respiratory symptoms such as a cough, sore throat, runny nose, and fever. However, the virus can lead to more severe disease in high-risk groups. Young children may develop bronchiolitis, while the elderly or immunocompromised patients may experience severe pneumonia [6].
HMPV infections often lead to hospitalization due to respiratory distress, especially in infants and elderly individuals, who are more susceptible to complications [7]. The disease can also be complicated by co-infections with other viruses like RSV or influenza, which can worsen the clinical presentation [8].
Pathogenesis
HMPV's pathogenicity stems from its ability to infect respiratory epithelial cells, triggering an immune response characterized by the release of inflammatory cytokines. The virus enters cells by binding to its receptors using the fusion (F) and glycoprotein (G) surface proteins, which allow viral entry and replication [9]. Once inside the host cell, HMPV triggers a local immune response, leading to inflammation and contributing to the clinical symptoms of airway obstruction, wheezing, and mucus production [10]. This inflammation plays a crucial role in the development of symptoms such as fever and difficulty breathing. Notably, HMPV infections do not always confer long-term immunity, as reinfections can occur throughout a person’s life [11].
Diagnosis
HMPV diagnosis is often challenging due to its clinical similarity to other viral respiratory infections. While conventional viral cultures and immunofluorescence assays can be used for detection, these methods are less sensitive compared to newer molecular techniques. The gold standard for diagnosing HMPV infection is polymerase chain reaction (PCR), which offers high sensitivity and specificity [12]. However, PCR testing is not universally available in all healthcare settings, which may hinder timely diagnosis. Additionally, serological testing can be helpful in detecting past infections, but it is not commonly used in acute cases [13].
Management
Currently, no antiviral treatments specifically target HMPV. Management is primarily supportive, including symptomatic relief such as fever control, hydration, and respiratory support for patients with more severe manifestations [14]. In critical cases, mechanical ventilation or supplemental oxygen may be necessary. Although there have been some investigations into the use of antiviral agents such as ribavirin, results have been inconsistent, and its use remains controversial [15]. Corticosteroids have been employed in some cases to reduce inflammation, but evidence regarding their efficacy in treating HMPV infections is limited [16].
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