Typical finding of human metapneumovirus infection is
Case 291
【Progress】
He was transported to national perinatal medical center because he had underground disease of hydrocephalus.
【Discussion】
Human metapneumovirus (HMPV) is one of the RNA viruses with envelope such as respiratory syncytial (RS) virus, influenza virus (1-3). HMPV infect epithelial cells of nasal, bronchus, and bronchiole. HMPV composes of genome RNA and messenger RNA (mRNA). Genome RNA is RNA itself and mRNA functions to form envelope protein. When HMPV goes into epithelial cell, HMPV is separated to genome RNA and mRNA. Genome RNA replicates in cytoplasm and mRNA attempts to create envelope protein in lysosome, endoplasmic reticulum and Golgi body. Lysosome functions to make immature protein, endoplasmic reticulum functions to induce immature protein to mature protein and Golgi body functions to attach glucose or lipid to protein, leading to make glycoprotein and lipoprotein (1-2). mRNA is, so to speak, a blueprint of envelope protein. mRNA from virus uses materials and factories in the infected cell for creating envelope protein.
HMPV infects respiratory endothelial cells, causing nasal fluids, cough, throat pain and fever. The latent term is 2 to 7 days and symptoms continue for appropriate 5 days (4, 5). It may be said HMPV is one of the viruses causing common cold (3).
It is reported that HMPV infection surges following RS infection (3-5). In fact, in our hospital, RS surged from June, reached to peak on August and September approaching to end on October, while HMPV appeared on September getting to peak on October. It is afraid that following infections of RS infection and HMPV, influenza infection might emerge and spread.
Surges of RS, HMPV and influenza did not occur in 2020 and 2021 when SARS-CoV-2 causing COVID19 was in pandemic worldwide. Now, they were coming to appear when COVID 19 pandemic was beginning to decline. It is mysterious where they live through during terms of COVID19 pandemic. Because the target cells for them including SARS-CoV-2 to infect were common respiratory epithelial cells, the situation of their simultaneous infection in a single person seems not often to occur for viruses survival competition. These viruses can infect from children to adults, indicating that when pandemic occurs by one of the virus, other virus might live through one another in a healthy person with inapparent infection.
Radiographic characteristics of HMPV infection are similar with them of other virus infection depending on damage extents of bronchial epithelial cells from focal necrosis to diffuse alveolar damages (4-6). When it occurs in bronchiole, bronchiolitis occurs reflecting radiographic image of intralobular ill-defined opacity (6). When it occurs in peripheral bronchus, it reflects radiologically ground glass opacity or consolidation. When it occurs in main bronchus, it reflects peri- or para-hilar opacity (6).
【Summary】
We presented fourteen-month-old infant for common cold. Serological findings revealed positive infection of human metapneumovirus (HMPV). Chest CT depicted peri-hilum opacity, consolidation and interlobular ill-defined opacity. It is borne in mind that HMVP, RSV, influenza and SARS-CoV-2 infect bronchial epithelial cells which pathologically cause focal necrosis to diffuse alveolar damages. Radiological findings differ based on location and extent of epithelial cell damages. In short, intralobular ill-defined nodules imply damages of bronchiole, collapse and consolidation do those of peripheral bronchus and peri-hilar opacity do those of main bronchus. HMVP, RSV, influenza and SARS-CoV-2 are RNA viruses: Genome RNA replicates in cytoplasm and mRNA , so to speak, a blueprint: immature protein for envelope is created in lysosome, mature protein is created in endoplasmic reticulum, and glycoprotein and lipoprotein are created in Golgi body.
【References】
1.Respiratory syncytial virus. From Wikipedia, the free encyclopedia
2.van den Hoogen, et al. "A newly discovered human pneumovirus isolated from young children with respiratory tract disease". Nature Medicine. 2001; 7: 719–724
3.Seema J, et al. Community-Acquired Pneumonia Requiring Hospitalization among U.S. Children. New England Journal of Medicine. 2015; 372 (9):835–845. . 2018 May-Jun;38(3):719-739
4.Williams, J V, et al. "Human Metapneumovirus and Lower Respiratory Tract Disease in Otherwise Healthy Infants and Children". New England Journal of Medicine. 2004; 350: 443–450
5.Williams, J V, et al. "The Role of Human Metapneumovirus in Upper Respiratory Tract Infections in Children: A 20-Year Experience". The Journal of Infectious Diseases. 2006;193: 387–395.
6.Koo HJ, et al. Radiographic and CT Features of Viral Pneumonia. Radiographics. 2018;38:719-739.
2023.2.21