bubble_chart Overview

Respiratory syncytial virus pneumonia, abbreviated as RSV pneumonia, is a common interstitial pneumonia in children, predominantly occurring in infants and young children. Since maternal antibodies cannot prevent infection, very young babies can contract the disease shortly after birth, though it is relatively rare in newborns. There have been occasional reports abroad of nosocomial infections leading to outbreaks in maternity hospital newborn wards.

bubble_chart Epidemiology

Respiratory syncytial virus (RSV) infection is extremely widespread. According to the results of serum IgG antibody detection by immunofluorescence in Beijing (1978): the positive rate in umbilical cord blood was 93%, 89% in newborns up to 1 month old, 40% in infants aged 1-6 months, over 70% in children aged 2 and 3 years, and around 80% in children aged 4 to 14 years (complement fixation tests yielded consistent results).

Since maternal antibodies cannot completely prevent infection, RSV pneumonia can occur at any time after birth. It is most common in children under 3 years old, with more severe cases seen in infants aged 1-6 months, and is more prevalent in males than females. In northern China, it occurs more frequently in winter and spring, while in Guangdong, it is more common in spring and summer. Because antibodies cannot fully prevent infection, reinfection with RSV is extremely common; one study observed a reinfection rate as high as 65% over 10 years. RSV is highly contagious, with reports of sequential infections among family members. When it occurs within a household, older children and adults typically experience upper respiratory tract infections. Literature reports indicate that the rate of nosocomial secondary RSV infection can be as high as 30-50%.

bubble_chart Etiology

Respiratory syncytial virus (RSV, also known as syncytial virus, belonging to the Paramyxoviridae family) is the most common pathogen causing viral pneumonia in children, leading to interstitial pneumonia and bronchiolitis. In Beijing, 48% of viral pneumonia cases and 58% of bronchiolitis cases were caused by RSV (1980–1984); in Guangzhou, 31.4% of childhood pneumonia and bronchiolitis cases were attributed to RSV (1973–1986); in the United States, 20–25% of infant pneumonia cases and 50–75% of bronchiolitis cases are caused by RSV.

Under electron microscopy, RSV appears similar to parainfluenza virus, with viral particles measuring approximately 150 nm, slightly smaller than parainfluenza virus. It is an RNA virus, sensitive to ether, lacks hemagglutination activity, and forms characteristic syncytia in human epithelial tissue cultures. The virus replicates in the cytoplasm, where cytoplasmic inclusion bodies can be observed. RSV has only one serotype, though recent molecular biology studies have identified two subtypes.

bubble_chart Pathological Changes

The incubation period for respiratory syncytial virus (RSV) infection is 2 to 8 days (typically 4 to 6 days). The hallmark of RSV pneumonia is mononuclear interstitial infiltration, primarily characterized by widening of alveolar septa and interstitial exudation dominated by mononuclear cells, including lymphocytes, plasma cells, and macrophages. Additionally, the alveolar spaces are filled with edema fluid, and the formation of hyaline membranes can be observed. In some cases, lymphocyte infiltration in the bronchiolar walls is also evident. In the lung parenchyma, edema with necrotic areas occurs, leading to alveolar filling, consolidation, and collapse. In a few cases, multinucleated syncytial cells resembling measles giant cells may be seen in the alveolar spaces, but no intranuclear inclusion bodies are found.

Gardner (1970) performed an autopsy on a child who died from RSV pneumonia and detected large amounts of RSV using tissue fluorescent antibody testing, with no evidence of human globulin deposition. He concluded that the pneumonic lesions were likely caused by direct damage from RSV rather than an allergic reaction.

bubble_chart Clinical Manifestations

This disease is commonly seen in infants and young children, with more than half occurring in babies under 1 year old. It is more prevalent in males than females, with a ratio of approximately 1.5-2:1. The incubation period is about 4-5 days. In the initial stage [first stage], cough and nasal congestion may be observed. About two-thirds of cases present with high fever, which can reach up to 41°C, but the fever is generally not persistent and can often be reduced with antipyretics. The duration of high fever is mostly 1-4 days, with a small number lasting 5-8 days. About one-third of affected children have grade II fever, which typically persists for 1-4 days. The febrile course in most cases lasts 4-10 days. In mild cases, respiratory distress and neurological symptoms are not prominent, while moderate to severe cases exhibit more noticeable respiratory distress, wheezing, cyanosis of the lips, nasal flaring, and retractions. A small number of severe cases may also develop complications such as heart failure. On chest auscultation, fine or coarse, medium rales are often heard, and percussion generally does not reveal dullness, though a few cases may show hyperresonance.

X-ray examination: Most cases show small patchy shadows, with large patchy shadows being extremely rare. About one-third of affected children exhibit varying degrees of lung qi swelling.

Blood count: The total white blood cell count generally ranges between (5-15)×10⁹/L (5000-15000/mm³), with most cases below 10×10⁹/L (10000/mm³). Neutrophils are mostly below 70%.

bubble_chart Diagnosis

In the past decade, respiratory syncytial virus (RSV) pneumonia and bronchiolitis have ranked first among viral pneumonias in infants and young children in China. The symptoms are clinically almost indistinguishable from parainfluenza virus pneumonia, mild influenza virus pneumonia, and mild adenovirus pneumonia. Severe influenza virus pneumonia and severe adenovirus pneumonia, however, present with persistent high fever, severe toxic symptoms, and significant respiratory symptoms, making their clinical manifestations far more severe than RSV pneumonia. The diagnosis of this disease primarily relies on virological and serological test results. In recent years, rapid diagnosis of RSV infection has been made possible through techniques such as indirect immunofluorescence using nasopharyngeal secretion exfoliated cells and serum IgM antibodies, ELISA, alkaline phosphatase anti-alkaline phosphatase bridging enzyme labeling (APAAP), biotin-avidin ELISA, horseradish peroxidase-anti-horseradish peroxidase (PAP), and monoclonal antibody fluorescence assays.

bubble_chart Treatment Measures

Special attention should be paid to general treatment, ensuring isolation, and striving to prevent secondary bacterial or other viral infections. If there is no secondary bacterial infection, treatment with Chinese medicine alone is sufficient. For general treatment, refer to the section on bronchopneumonia; other aspects can be referred to in the section on adenovirus pneumonia. Since this disease is relatively mild, extensive symptomatic and supportive therapies are unnecessary.

Regarding antiviral chemical drugs, for more severe cases, ribavirin aerosol therapy can be used. Please refer to the overview of viral pestilence in the previous volume. Recently, some foreign studies have reported the effectiveness of short-term high-dose aerosol therapy for respiratory syncytial virus (RSV) infections. Additionally, in recent years, Xinhua Hospital in Shanghai has used whey solution (diluted colostrum) for aerosol therapy in lower respiratory tract infections caused by RSV. Wenzhou Medical College has extracted SIgA from colostrum for aerosol inhalation to treat respiratory syncytial virus pneumonia, achieving favorable results, which can be applied in practice.

bubble_chart Prognosis

The disease is generally mild, with clinical recovery in 6 to 10 days for simple cases, and X-ray shadows typically disappearing within 2 to 3 weeks. If isolation measures are inadequate, secondary infections are likely, leading to recurrent fever. Death from simple respiratory syncytial virus pneumonia is extremely rare.