Comment: hMPV joins RSV and influenza as a respiratory virus that has had an increase, which appears to be related to the COVID pandemic effects on the population.
Comment: Small single-center retrospective study of outcomes among HSCT recipients with RSV or hMPV (47 patients with RSV and 24 with hMPV) in Germany. The decision for antiviral treatment was at the discretion of the attending physician. All 30 patients with primary LRTI and 10 patients with secondary LRTI were treated with ribavirin, 95% with the intravenous formulation. 45% of these patients received additional treatment with intravenous immunoglobulins. 11.5% suffered a virus-associated death. Sixty-day mortality was significantly higher in the immunodeficiency scoring index (ISI) high-risk group (log-rank P = .05). Mortality was independent of the type of virus (P = .817). Treatment of LRTI with intravenous ribavirin resulted in a similar outcome in RSV- and hMPV-infected patients. No benefit detected regarding adjunctive treatment with immunoglobulins.
Rating: Important
Comment: A prospective observational study of adult patients admitted with severe hMPV-CAP (n=50) and severe Influenza-CAP (n=109) to a single center in South Korea between 2010 and 2017.
Mortality was similar between both groups. Oral ribavirin was not associated with improved outcome (60-day mortality: ribavirin therapy group 35.0% [7/20] vs. no ribavirin therapy group 30.0% [9/30], p = 0.71). Subgroup analyses showed no significant differences in mortality among non-immunocompromised and immunocompromised patients.
Rating: Important
Comment: Retrospective large cohort study from a single enter in South Korea. The authors compared outcomes of patients admitted with CAP and found to have hMP or flu. hMPV was less common than flu (3.2% vs. 7.0% among 1559 patients with severe CAP). The mortality rates were not significantly different between the two groups (30-day mortality: 24.0% vs. 32.1%, p = 0.30; 60-day mortality: 32.0% vs. 38.5%, p = 0.43). Oral ribavirin therapy was not associated with improved outcome (60-day mortality: ribavirin therapy group 35.0% [7/20] vs. no ribavirin therapy group 30.0% [9/30], p = 0.71). Subgroup analyses showed no significant differences in mortality among non-immunocompromised (60-day mortality: hMPV 25.6% vs. flu 31.1%, p = 0.55) and immunocompromised patients (60-day mortality: hMPV 54.5% vs. 54.3%, p = 0.99). The length of ICU and hospital stay did not differ between groups.
Rating: Important
Comment: Among children < 5 years, most had parahilar inflitrates if they had an abnormal CXR. Consolidative picture was less common.
Comment: The findings of 2 or more viruses in this study, comprising 19 papers, did not indicate an increased severity of illness.
Comment: In this study of 128 pts with hMPV infection, 31% required ICU care and hMPV was considered likely cause in 38% and possibly the cause in 55%. ARDs criteria were seen in 48% of these patients. Many of these adult patients had an underlying cardiopulmonary disease but also afflicted some without any co-morbidities.
Comment: Nasal swabs recovered hMPV equally as well as oropharyngeal swabs for molecular detection, but using both appears to increase yield by no more than 10%.
Comment: Population-based surveillance study of adults 18 years of age or older requiring hospitalization for community-acquired pneumonia among five hospitals in Chicago and Nashville. The study reveals that viruses were detected in 23% of cases, and co-detection of bacteria and viruses occurred in 3%. hMPV was the third most common virus isolated after rhinovirus and influenza.
Rating: Important
Comment: A review article is comprehensive. Some interesting tidbits: 4% of adult infections are asymptomatic. Humoral immunity produced and antibody responses may be cross-protective.
Comment: In adults with pneumonia, typically in elderly or immunocompromised patients, interstitial radiographic changes are observed, along with leukopenia and elevated liver function tests (LFTs). Rates of ICU care, mechanical ventilation, and other similar measures are comparable to those in this population for RSV and influenza.
Comment: A multinational prospective study in children < 5 yrs; HMPV detected in 200 of 3490 hospitalized children (6%), 222 of 3257 children in outpatient clinics (7%), 224 of 3001 children in the emergency department (7%), and 10 of 770 asymptomatic controls (1%). Hospitalized children tended to be older and have diagnoses such as pneumonia or asthma requiring supplemental oxygen. Most children had no underlying chronic health problems. The authors conclude that hMPV results in a significant number of both inpatient and outpatient visits.
Rating: Important
Comment: A Canadian study found 58 of 305 outpatient children (19.0%) and 69 of 734 hospitalized children (9.4%) infected with hMPV, second only to RSV (48.2% and 63.6%, respectively). In the multivariate regression analysis of hMPV cases, age < 6 months and household crowding were associated with hospitalization. Among hospitalized patients, risk factors for severe hMPV disease were female sex, prematurity, and genotype B infection.
Comment: Comprehensive review with 263 references highlighting important scientific and clinical advances since the discovery of human metapneumovirus in 2001. There is little evidence to support any specific treatment recommendations. Generally, supportive care is advised. Authors include the discoverer of the virus as well as many key investigators and clinicians.
Comment: The authors describe nine patients at their institution who were immunocompromised and suffering from human metapneumovirus infection. They state that two of these patients were successfully treated with ribavirin (aerosolized) and polyclonal human immunoglobulin. I believe they are quite overstating the case that all should be considered for therapy with severe disease given lack of prospective, randomized trials especially given the expense and the difficulties of administering aerosolized ribavirin.
Comment: A study from Nashville, TN in 1104 children hospitalized found HMPV in 3.8% of children with respiratory tract infection or fever. This was similar to the influenza virus and parainfluenza virus 3.
Comment: One of several studies showing that viral coinfection is not infrequent in adults hospitalized for pneumonia. In this multicenter study of 193 patients, 7 (3.6%) had recovery of hMPV.
Comment: A hypothesis-generating study suggests that severe hHMPV infection may be due to co-infection with the pneumococcus. Study examined 2715 episodes of LRTI in children, and found in those who were fully immunized with PCV, hMPV-associated LRTI was reduced by 45% (95% confidence interval [CI], 19%-62%; P = .002), and the incidence of clinical pneumonia was reduced by 55% (95% CI, 22%-74%; P = .003). Similarly, in fully vaccinated HIV-infected children, the incidence of hMPV-associated LRTI was reduced by 53% (95% CI, 3%-77%; P = .035), and that of clinical pneumonia was reduced by 65% (95% CI, 19%-85%; P = .020).
Comment: The animal model is suggestive that ribavirin with corticosteroids yields some benefit. There is no similar human evidence, so there cannot be any reasonable recommendation for the use of ribavirin at this time.
Comment: Although most viral illnesses in this age group are due to RSV, this study suggests that co-infection with hMPV + RSV yields more severe illness, including those in the ICU.
Comment: The initial description of hMPV, isolating the virus from children with unexplained RTIs. Sequencing suggests that the virus is closely related to avian metapneumovirus (a cause of rhinotracheitis and swollen head syndrome in chickens).
Rating: Important