Human metapneumovirus infection in pregnant and postpartum women: Clinical characteristics, risk factors and severity

Abstract

Background: Since its isolation in 2001, Human Metapneumovirus (hMPV) has emerged as a cause of respiratory illness worldwide. While hMPV incidence varies based on location and time of year, it has been found responsible for an estimated 1.5-10.5% of respiratory infections among adults. To our knowledge, hMPV’s risk factors, clinical manifestations and severity have never been described among pregnant and postpartum women; this thesis seeks to address this research gap. Methods: As part of a community-based randomized controlled trial of seasonal influenza vaccination in rural southern Nepal, pregnant women were enrolled and visited weekly through six months postpartum. If an episode of respiratory illness with fever occurred in the prior week, a mid-nasal swab was collected. Risk factors were assessed using a multivariate Cox regression model. To assess severity, a 1-point score was assigned to each symptom (fever, cough, sore throat, rhinorrhea, myalgia); a Wilcoxon rank-sum test was used to compare the severity scores and symptom duration between groups. Results: During the 3-year study period, 56 of 3693 women enrolled (1.5%) had hMPV detected. The overall incidence of hMPV in the study sample was 15 cases/1000 person-years; this represents 26 cases (1.3% incidence) among pregnant women and 30 cases (1.8% incidence) among postpartum women. HMPV incidence peaked between September 2011 and January 2012. Maternal education duration was significantly associated with hMPV, with additional years of education associated with decreased risk (HR 0.93; 95% CI 0.87, 0.99). Overall, the most common symptom was cough (64.2%), followed by myalgia (60.7%). While the severity score did not differ significantly between groups, pregnant women experienced longer duration of symptoms (6.5 days vs 4.5 days; p = 0.03). Conclusion: HMPV is a significant cause of respiratory illness in pregnant and postpartum women in rural Nepal. Women with fewer years of education experienced greater risk of infection. Pregnant women experienced significantly increased symptom duration compared to postpartum women.