Respiratory syncytial virus (RSV) is a common and easily spread virus that infects the lungs and airways. It is a major cause of respiratory illness around the world, especially in infants and young children, but it can also affect older adults and people with weak immune systems. Almost all children come into contact with RSV by the age of two. In most cases, it causes mild, cold-like symptoms, but in some children and vulnerable adults, it can lead to serious illness that requires hospital care.
People at higher risk of severe RSV infection include premature babies, children with heart or lung problems, older adults, and those with weakened immune systems. In these groups, RSV can cause serious lung infections such as bronchiolitis (inflammation of the small airways) and pneumonia, and in rare cases, it can lead to respiratory failure or death.
The illness usually begins with mild symptoms like a runny nose, cough, sneezing, sore throat, and fever. As it worsens, symptoms may include wheezing, difficulty breathing, fast breathing, bluish skin from lack of oxygen (a sign called cyanosis), and loss of appetite, particularly in infants. Severe cases can cause dehydration and breathing problems that may require hospital treatment and oxygen support.
There is no specific cure for RSV, so treatment mainly helps relieve symptoms. Most mild infections can be managed at home with rest, fluids, and fever-reducing medicines such as acetaminophen (paracetamol) or ibuprofen. Severe cases may need hospital care for oxygen therapy, breathing support, or fluids given through a vein. In certain high-risk patients, doctors may use an antiviral medicine called ribavirin, though it is not widely used. For prevention, special antibody treatments such as palivizumab and nirsevimab are available to protect infants who are more likely to develop severe disease.
RSV spreads through droplets from coughing or sneezing and by touching contaminated surfaces. Preventive steps include frequent handwashing, cleaning surfaces, avoiding close contact with sick people, and covering the mouth and nose when coughing or sneezing. Recently, new RSV vaccines such as Abrysvo and Arexvy have been approved for older adults and for use during pregnancy to protect newborns after birth.
History and Discovery
Respiratory syncytial virus (RSV) was first identified in 1956 during studies of respiratory infections in chimpanzees at the Walter Reed Army Institute of Research in the United States. The virus was initially named chimpanzee coryza agent because it caused symptoms similar to the common cold (coryza) in the animals. Shortly after its discovery, the same virus was isolated from infants suffering from bronchitis and pneumonia, confirming its role as a major human pathogen. This finding marked a turning point in pediatric medicine, as RSV quickly became recognized as one of the most important causes of respiratory infections in children worldwide.
By the late 1950s and early 1960s, researchers established that RSV was a leading cause of lower respiratory tract infections, especially bronchiolitis (inflammation of the small airways) and pneumonia, in infants and young children. Early epidemiological studies showed that almost all children were infected with RSV by the age of two, and that reinfections could occur throughout life. Seasonal patterns were soon noted, with RSV outbreaks occurring mainly in the late fall, winter, and early spring months in temperate regions, while tropical regions experienced peak transmission during the rainy season. These seasonal epidemics have continued to place significant pressure on healthcare systems, particularly pediatric wards, during RSV season.
Throughout the latter half of the twentieth century, RSV became a subject of intense research due to its public health impact. Efforts to develop an effective vaccine began in the 1960s, but an early attempt using a formalin-inactivated RSV vaccine led to unexpected severe illness in vaccinated children when they were later exposed to the virus. This tragic outcome delayed vaccine research for decades and reshaped the understanding of immune responses to respiratory viruses. Advances in molecular biology and immunology in the 1990s and 2000s eventually revived vaccine development, leading to the recent approval of safe and effective vaccines for adults and pregnant women.
RSV Classification
Respiratory syncytial virus is classified within the family Pneumoviridae and the genus Orthopneumovirus. It is an enveloped, single-stranded, negative-sense RNA virus, meaning its genetic material must be converted into a positive-sense RNA strand before it can be used to make viral proteins. The virus is approximately 150 to 300 nanometers in diameter and has a spherical or pleomorphic shape surrounded by a lipid envelope derived from the host cell membrane. Embedded in this envelope are surface glycoproteins that play essential roles in infection and immunity.
The most important structural proteins include the fusion (F) protein, which allows the virus to fuse with host cells and form large, multinucleated cells called syncytia, a feature that gave RSV its name, and the attachment (G) glycoprotein, which helps the virus bind to host cell receptors. The matrix (M) protein maintains viral structure, while the nucleoprotein (N), phosphoprotein (P), and large polymerase (L) are responsible for replication and transcription of the viral genome.
RSV is divided into two major subtypes, RSV-A and RSV-B, which are distinguished by genetic and antigenic differences, particularly in the G glycoprotein gene. Both subtypes co-circulate during seasonal outbreaks, though one subtype may dominate in a given year or region. RSV-A is often associated with more severe disease, but both types contribute significantly to the global disease burden. Continuous genetic variation in these subtypes allows RSV to evade immune responses, leading to recurrent infections throughout life.
RSV shares close evolutionary relationships with other members of the Pneumoviridae family, including the human metapneumovirus (HMPV), which causes similar respiratory illnesses.
Causes and Transmission
Respiratory Syncytial Virus (RSV) spreads primarily through direct contact and respiratory secretions. Certain populations are more vulnerable to infection due to biological and environmental factors. Infection rates also vary depending on seasonal changes and geographic location.
Modes of Transmission
RSV spreads mainly through respiratory droplets and direct contact with infectious secretions from the nose or throat of an infected individual. Transmission often occurs when a person inhales droplets expelled by coughing or sneezing, or when they touch contaminated surfaces and subsequently touch their eyes, nose, or mouth. The virus is capable of surviving for several hours on hard, nonporous surfaces such as tables, crib rails, and doorknobs, and for shorter periods—typically 30 minutes or less—on hands and soft materials like tissues or clothing.
Indirect transmission plays a significant role in both household and healthcare settings. Hand-to-face transfer is one of the most common routes of infection, emphasizing the importance of regular handwashing and proper hygiene practices. Close physical contact, such as hugging, kissing, or sharing utensils with infected individuals, also facilitates viral spread.
In healthcare environments, particularly pediatric wards, neonatal intensive care units (NICUs), and long-term care facilities, RSV can spread rapidly due to the presence of vulnerable individuals and frequent person-to-person interaction. Outbreaks in these settings have been documented to occur through inadequate hand hygiene, improper use of personal protective equipment (PPE), and contamination of medical instruments. For this reason, healthcare facilities implement strict infection control protocols such as isolation of infected patients, use of droplet precautions, and environmental disinfection to prevent nosocomial transmission.
Community transmission is common in crowded settings such as daycare centers, schools, and homes with multiple children. Infants and young children often acquire RSV from older siblings or caregivers who carry and shed the virus, even if they show only mild symptoms. Adults can also transmit RSV to infants, acting as reservoirs of infection during seasonal epidemics.
Risk Factors for Infection
While RSV can infect people of all ages, certain populations are more susceptible to severe illness due to biological, developmental, or environmental factors.
Infants and young children represent the group most frequently affected by RSV. Almost all children encounter the virus by the age of two, but infants younger than six months are at greatest risk for hospitalization. Their smaller airways and immature immune systems make them more prone to airway obstruction and respiratory distress. Premature infants, in particular, are at elevated risk because of underdeveloped lungs and reduced maternal antibody transfer, which limits their immune protection.
Children with underlying health conditions, such as congenital heart disease, chronic lung disease (including bronchopulmonary dysplasia), or neuromuscular disorders, face a higher likelihood of severe infection and prolonged recovery. Similarly, immunocompromised individuals, including those undergoing chemotherapy, bone marrow or organ transplantation, or living with HIV/AIDS may experience prolonged viral shedding and life-threatening complications.
Among adults, older individuals aged 65 and above and those with chronic cardiopulmonary conditions like chronic obstructive pulmonary disease (COPD) or congestive heart failure are particularly vulnerable. RSV infection in these groups often leads to exacerbations of existing health problems, increased hospitalization rates, and higher mortality compared to healthy adults.
Environmental and social factors also contribute to infection risk. Exposure to tobacco smoke, both prenatal and postnatal, impairs airway defense mechanisms and increases susceptibility to respiratory infections.
Seasonality Patterns
RSV infections display distinct seasonal patterns influenced by climate, geography, and population behavior. In temperate regions, outbreaks typically occur from late fall to early spring, with the highest activity during winter months. These periods coincide with increased indoor crowding and lower humidity, which enhance viral survival and transmission.
In tropical and subtropical regions, RSV circulation may occur year-round, but activity often peaks during or shortly after rainy seasons, when humidity and indoor gatherings increase. In arid climates, outbreaks may correspond with cooler months or seasonal changes that alter human social patterns.
Seasonal patterns influence healthcare planning and prevention strategies. Surveillance data helps predict outbreak timing and allocate resources efficiently. Vaccination efforts and prophylactic treatments are often timed to coincide with peak RSV activity.
Symptoms and Clinical Manifestations
Respiratory Syncytial Virus (RSV) primarily affects the respiratory system, causing symptoms that vary by age and health status. Manifestations range from mild cold-like signs to severe respiratory distress, especially in vulnerable populations.
Common Symptoms in Children
Children with RSV often exhibit symptoms similar to a cold initially. These include runny nose, cough, sneezing, and mild fever. Feeding difficulties and irritability are common in infants.
As the infection progresses, some develop wheezing or rapid breathing due to inflammation in the lower respiratory tract. Bronchiolitis is a frequent complication, particularly in infants under six months.
Symptoms can last 1-2 weeks. Close monitoring is essential if the child experiences difficulty breathing, poor hydration, or persistent high fever.
Symptoms in Adults and Elderly
Adults with RSV generally present with mild cold-like symptoms, such as a runny nose, sore throat, and cough. Fever is less common but may occur.
Older adults, especially those with chronic heart or lung disease, may experience more severe symptoms, including shortness of breath and worsening of underlying conditions like COPD or asthma.
Fatigue and muscle aches sometimes accompany the respiratory symptoms. Duration typically lasts about 1-2 weeks but complications can prolong recovery in at-risk individuals.
Severe RSV Infections
Severe RSV infection can lead to bronchiolitis or pneumonia. Key signs include severe respiratory distress, such as rapid or labored breathing, nasal flaring, or chest retractions.
Hypoxemia (low blood oxygen) may cause cyanosis (bluish skin). Infants and immunocompromised patients are at highest risk for severe illness.
Hospitalization may be necessary for oxygen therapy and supportive care. Mechanical ventilation can be required in critical cases. Early detection of severe symptoms is vital for prompt treatment.
Pathophysiology of RSV Infection
Respiratory Syncytial Virus (RSV) primarily infects the epithelial cells that line the respiratory tract, particularly those of the nasopharynx, trachea, bronchi, and bronchioles. The infection begins when the virus attaches to the surface of these cells using its two key surface glycoproteins—the G (attachment) protein and the F (fusion) protein. The G protein enables the virus to bind to host cell receptors, while the F protein mediates the fusion of the viral envelope with the host cell membrane, allowing the viral genetic material to enter the cell. The F protein is also responsible for the fusion of infected cells with neighboring ones, forming syncytia—large, multinucleated cells characteristic of RSV infection and the origin of the virus’s name.
Once inside the cell, RSV undergoes replication in the cytoplasm, where it synthesizes new viral RNA and proteins. This replication process leads to cell damage and death, disrupting the integrity of the airway epithelium. As infected cells die and slough off, they contribute to airway obstruction, particularly in the small bronchioles of infants and young children. This obstruction results from a combination of cellular debris, mucus overproduction, and inflammation, which together impede airflow and gas exchange.
Immune Response and Inflammation
The body’s immune system mounts a strong response to RSV infection involving both innate (immediate) and adaptive (long-term) immune mechanisms. The innate immune response is activated shortly after infection when the epithelial cells recognize viral components through pattern recognition receptors (PRRs) such as toll-like receptors. This recognition triggers the release of cytokines and chemokines, signaling molecules that attract immune cells such as neutrophils, macrophages, and natural killer (NK) cells to the site of infection.
While these immune cells help control viral replication, their activity also contributes to inflammation of the airway walls. The infiltration of immune cells and the release of inflammatory mediators cause swelling (edema), increased mucus production, and narrowing of the bronchioles, all of which exacerbate breathing difficulties. The inflammation-induced hypersecretion of mucus can block the smaller airways, leading to wheezing, coughing, and hypoxia (low oxygen levels in the blood).
In the adaptive immune phase, T cells play a critical role in clearing infected cells, while B cells produce neutralizing antibodies that target RSV’s surface glycoproteins. However, the immune response does not confer long-lasting protection; reinfections are common throughout life due to incomplete immunity and the virus’s ability to vary its surface proteins.
Cellular Damage and Airway Obstruction
Microscopically, RSV infection leads to necrosis (cell death) and desquamation (shedding) of the respiratory epithelium, exposing the underlying basement membrane. The loss of ciliated cells—the cells responsible for clearing mucus and debris—impairs the normal mucociliary clearance mechanism, allowing mucus and sloughed cells to accumulate in the airways. This buildup is particularly problematic in infants, whose smaller bronchioles are easily obstructed. As a result, air becomes trapped in the lungs during exhalation, causing hyperinflation and sometimes atelectasis (collapse of lung tissue).
The resulting airway obstruction and inflammation can lead to bronchiolitis, the most common severe manifestation of RSV in infants. This condition is marked by rapid, shallow breathing, wheezing, and difficulty feeding due to respiratory distress. In severe cases, reduced oxygen exchange can cause hypoxemia and require hospitalization for oxygen therapy or mechanical ventilation.
| Key Pathophysiologic Features | Description |
| Viral Entry | G protein attachment, F protein fusion |
| Cellular Damage | Epithelial cell death and sloughing |
| Inflammatory Response | Cytokine release, immune cell infiltration |
| Airway Obstruction | Mucus accumulation and edema |
Diagnosis of RSV
Diagnosing RSV involves a combination of clinical signs, laboratory confirmation, and imaging when necessary. Each approach provides critical information to distinguish RSV from other respiratory illnesses and guides treatment.
Clinical Evaluation
Clinical diagnosis begins with a thorough assessment of symptoms and patient history. Typical manifestations of RSV include cough, nasal congestion, wheezing, and fever. In infants and young children, additional signs such as tachypnea (rapid breathing), nasal flaring, chest wall retractions, and feeding difficulties often indicate lower respiratory tract involvement, such as bronchiolitis or pneumonia.
A clinician’s physical examination may reveal diffuse crackles, wheezes, or decreased breath sounds on auscultation of the lungs. Pulse oximetry is frequently used to evaluate oxygen saturation levels, particularly in pediatric or elderly patients with respiratory distress. While clinical evaluation provides strong suspicion for RSV, symptom overlap with other viral infections makes confirmatory testing necessary.
Risk assessment based on patient demographics, medical history, and known community outbreaks also aids diagnosis. Infants, immunocompromised individuals, and older adults with chronic heart or lung conditions are considered high-risk groups and often warrant more intensive diagnostic testing.
Laboratory Testing
Laboratory confirmation is the cornerstone of RSV diagnosis. The most common sample type is a nasopharyngeal swab or aspirate, though throat swabs and lower respiratory specimens may be collected in severe cases.
1. Rapid Antigen Detection Tests (RADTs):
These point-of-care tests detect RSV antigens and provide results within an hour, allowing for quick clinical decisions. However, their sensitivity is lower in older children and adults due to reduced viral shedding.
2. Molecular Testing (RT-PCR):
Reverse transcription polymerase chain reaction (RT-PCR) assays are the current gold standard for RSV detection. They are highly sensitive and specific, capable of identifying even low viral loads. Multiplex RT-PCR panels can simultaneously detect RSV and other respiratory viruses, improving diagnostic efficiency during outbreak seasons.
3. Viral Culture:
Although historically used for RSV diagnosis, viral culture has largely been replaced by molecular methods due to its longer turnaround time (typically several days) and lower sensitivity. It remains useful for research and epidemiological purposes.
4. Serological Testing:
Serology, which detects RSV-specific antibodies, is rarely employed in acute clinical settings but may be utilized for retrospective diagnosis or population-level studies to understand immunity and exposure patterns.
Imaging Techniques
Imaging plays a supportive role in RSV diagnosis, primarily in evaluating disease severity or complications rather than confirming the presence of the virus.
Chest X-rays are the most frequently used imaging tool and can reveal findings such as hyperinflated lungs, peribronchial thickening, patchy atelectasis, or, in severe cases, areas suggestive of pneumonia. These findings reflect airway obstruction and inflammation typical of RSV bronchiolitis.
Computed Tomography (CT) scans are rarely required and are reserved for cases with atypical presentations, suspected secondary bacterial infections, or when structural lung abnormalities must be excluded.
Imaging helps assess the extent of pulmonary involvement and guides clinical decisions in hospitalized patients but is unnecessary for routine diagnosis in mild cases.
Treatment and Management Strategies
Treatment of Respiratory Syncytial Virus (RSV) focuses primarily on easing symptoms and preventing complications. Medical intervention varies from basic supportive measures to specific pharmacological options based on patient risk and severity.
Supportive Care Approaches
Supportive care is the mainstay for most RSV cases, especially in infants and young children. Oxygen therapy is indicated when hypoxemia (low blood oxygen levels) occurs. Supplemental oxygen is commonly administered through a nasal cannula, oxygen mask, or high-flow nasal oxygen systems in hospital settings. Continuous pulse oximetry is often employed to monitor oxygen saturation in infants and patients with respiratory distress. In severe cases, mechanical ventilation or non-invasive positive pressure ventilation (NIPPV) may be necessary to support breathing, particularly in patients with acute respiratory failure or apnea episodes.
Hydration management is equally vital. Because RSV infection can cause poor feeding and increased insensible fluid loss due to rapid breathing and fever, ensuring adequate fluid balance is critical. Mildly affected patients can maintain hydration orally, while those with significant respiratory compromise may require intravenous (IV) fluids to prevent dehydration and electrolyte imbalances.
Airway clearance techniques are also important, particularly in infants whose smaller airways can become easily obstructed by mucus. Gentle nasopharyngeal suctioning is used to remove secretions and improve airflow. Excessive suctioning, however, is avoided as it can irritate the mucosa and exacerbate inflammation.
Fever and discomfort management typically involve the use of antipyretics such as acetaminophen or ibuprofen. These medications relieve discomfort, reduce fever, and improve feeding behavior. Antibiotics are not indicated unless there is clinical or laboratory evidence of a secondary bacterial infection, such as otitis media or bacterial pneumonia.
Close monitoring of respiratory status is essential, especially in infants under six months of age or those with underlying cardiopulmonary disease. Hospitalization is considered when patients exhibit severe respiratory distress, persistent hypoxemia, poor feeding, apnea, or dehydration.
Pharmacological Treatments
As of now, no specific antiviral therapy has been approved for widespread use against RSV in the general population. Treatment remains primarily supportive, but several pharmacologic options are used in selected cases or under specific circumstances.
Ribavirin, a broad-spectrum antiviral, has been used in certain severe RSV cases, particularly among immunocompromised patients or those with life-threatening lower respiratory tract infections. However, due to inconsistent clinical benefits, high cost, and potential toxicity (including hemolytic anemia and teratogenicity), its routine use is not recommended. Ribavirin may be considered only in severely ill or immunocompromised individuals under close medical supervision.
Palivizumab, a humanized monoclonal antibody, is not used for treatment but for prophylaxis against severe RSV disease in high-risk infants and young children. It works by binding to the F (fusion) protein of the virus, preventing its entry into host cells. Palivizumab is administered intramuscularly once a month throughout the RSV season, typically for up to five doses. It reduces hospitalization rates and disease severity but does not cure or eliminate active infection.
Bronchodilators, such as albuterol, have been evaluated for RSV-related bronchiolitis; however, evidence does not support their routine use. They may offer transient relief in patients with an underlying reactive airway disease or asthma-like symptoms, but their effect on oxygenation or overall clinical outcomes is minimal. Therefore, a therapeutic trial may be justified in select patients, with continued use only if a clear clinical benefit is observed.
Corticosteroids, both systemic and inhaled, are generally not recommended for RSV treatment. Studies have shown no consistent benefit in reducing symptom duration or improving clinical outcomes. Exceptions may include cases with concurrent asthma exacerbations or severe airway inflammation requiring anti-inflammatory support.
Antibiotics play no role in treating viral RSV infection but may be used when there is clear evidence of secondary bacterial complications, such as bacterial pneumonia, sinusitis, or otitis media. Empirical use without confirmation is discouraged, as it contributes to antimicrobial resistance.
Prevention and Control Measures
Effective prevention and control of RSV involves targeted actions to reduce transmission in healthcare environments and the use of specific immunizations for at-risk populations. Both approaches focus on interrupting the virus’s spread and protecting vulnerable groups.
Infection Prevention in Healthcare Settings
The use of personal protective equipment (PPE), including gloves, gowns, and masks, is recommended when caring for individuals with suspected or confirmed RSV infection. Proper donning and removal of PPE help prevent inadvertent self-contamination and transmission to others. In addition, contact and droplet precautions are enforced for infected patients. These precautions typically involve isolating affected individuals in private rooms or cohorting them with other RSV-positive patients to minimize cross-infection.
Environmental cleaning and disinfection play an equally important role. Hospital-grade disinfectants should be used to clean frequently touched surfaces, medical devices, and shared equipment, as the virus can persist on objects such as bed rails, door handles, and stethoscopes. Increased cleaning frequency is recommended during RSV outbreaks, particularly in high-risk wards.
Staff education and training are essential components of infection control. Healthcare personnel should receive ongoing instruction on RSV transmission dynamics, early symptom recognition, and proper implementation of control measures.
During outbreaks or heightened RSV activity, additional precautions may be introduced, such as restricting non-essential visits in neonatal and pediatric units, conducting visitor health screenings, and reinforcing the use of masks in communal areas.
Vaccination and Immunoprophylaxis
While no universally available vaccine for RSV currently exists, immunoprophylaxis provides a critical line of defense for specific high-risk groups, particularly infants and young children with underlying medical conditions.
Palivizumab, a humanized monoclonal antibody, is the primary preventive agent used to reduce the severity of RSV disease. It is indicated for premature infants (born at or before 35 weeks of gestation), children under two years of age with chronic lung disease, and those with significant congenital heart disease. The drug is administered via intramuscular injection once a month throughout the RSV season, which typically spans the late fall to early spring months in temperate regions.
Clinical studies have demonstrated that palivizumab significantly decreases hospitalization rates and severe RSV-related complications among eligible infants. However, it does not prevent infection entirely and is not used as a general vaccine. Due to its high cost and limited duration of protection, its use is generally restricted to those with the greatest medical vulnerability.
In 2023, regulatory approvals in some countries introduced the first RSV vaccines for adults aged 60 and older, as well as for pregnant women in late gestation, marking a major advancement in preventive medicine. These vaccines work by inducing immunity against the RSV F (fusion) protein, which plays a critical role in viral entry into host cells.
Routine prophylaxis and vaccination recommendations should follow official public health guidelines, such as those issued by the World Health Organization (WHO), the U.S. Centers for Disease Control and Prevention (CDC), or local health authorities.
RSV in Special Populations
Respiratory Syncytial Virus presents distinct challenges in certain groups due to their vulnerable immune systems or developmental stages. The impact, severity, and management strategies vary significantly between these populations.
Infants and Young Children
RSV is one of the most common causes of serious respiratory illness in infants and young children worldwide. Nearly all children are infected with RSV by their second birthday, but the severity of illness depends on age, immune maturity, and underlying health. Infants under six months old are particularly vulnerable because their airways are smaller, their immune systems are still developing, and they are unable to clear mucus effectively. When RSV infects the lower respiratory tract, it often causes bronchiolitis—inflammation and blockage of the tiny air passages in the lungs—which can lead to wheezing, rapid breathing, and difficulty feeding.
Premature infants are at especially high risk because their lungs are underdeveloped, and they often have weaker immune defenses. In addition, babies with congenital heart disease or chronic lung disease (such as bronchopulmonary dysplasia) are more likely to develop severe complications, including respiratory failure. Hospitalization rates for these groups are significantly higher during RSV season, and many require oxygen therapy, intravenous fluids, or mechanical ventilation for recovery.
Recurrent infections are also common. Although the first RSV infection provides some immunity, protection is incomplete, and reinfections can occur throughout childhood. These subsequent infections are usually milder but can still cause significant illness in children with ongoing medical conditions. Long-term studies have suggested that severe RSV infection in infancy may increase the risk of developing asthma or chronic wheezing later in life.
Preventive strategies for this group include maternal vaccination during pregnancy, which allows antibodies to pass to the fetus and provide protection after birth, and the use of monoclonal antibodies such as palivizumab and nirsevimab for high-risk infants during RSV season. Maintaining good hygiene, avoiding exposure to sick individuals, and ensuring proper breastfeeding and nutrition also contribute to lowering infection risk.
Immunocompromised Individuals
RSV infection can be particularly dangerous in people with weakened immune systems, as their bodies have reduced ability to fight off viruses and clear infections. This group includes patients receiving chemotherapy for cancer, organ or stem cell transplant recipients, and individuals with advanced HIV/AIDS or genetic immunodeficiency disorders. In these patients, RSV often progresses from a mild upper respiratory illness to a severe lower respiratory tract infection, sometimes leading to pneumonia or respiratory failure.
A key feature of RSV in immunocompromised hosts is prolonged viral shedding, meaning the virus remains active and detectable for an extended period, increasing the likelihood of transmission and recurrent infections. These patients are also at a greater risk for secondary bacterial infections, such as bacterial pneumonia or sepsis, which can further complicate treatment.
Management in immunocompromised individuals often requires hospitalization and close monitoring. Supportive therapies such as oxygen supplementation, intravenous fluids, and nutritional support are essential. In severe cases, antiviral drugs like ribavirin may be used, although their effectiveness is limited and typically reserved for life-threatening infections. The use of immune globulin or monoclonal antibodies may also be considered as part of prevention or treatment in select patients.
Outcomes and Complications of RSV
Respiratory Syncytial Virus (RSV) typically causes mild, cold-like symptoms in healthy individuals. Most recover fully within one to two weeks without complications.
However, RSV can lead to severe outcomes in infants, the elderly, and those with weakened immune systems. These groups are at higher risk for serious respiratory illnesses such as bronchiolitis and pneumonia.
Severe Lower Respiratory Tract Disease
In vulnerable individuals, RSV is a leading cause of bronchiolitis and pneumonia, two conditions that can significantly affect breathing and oxygen exchange.
- Bronchiolitis involves inflammation and blockage of the smallest airways in the lungs, known as bronchioles. This causes wheezing, rapid breathing, chest retractions (the visible pulling in of the skin between ribs), and difficulty feeding in infants. It is the most common cause of hospitalization in infants during the RSV season.
- Pneumonia occurs when the infection spreads deeper into the lung tissue, leading to fluid accumulation, fever, persistent cough, and difficulty breathing. RSV pneumonia can be life-threatening in infants, older adults, and those with underlying lung or heart disease.
Severe and Life-Threatening Complications
In some cases, RSV infection can progress to acute respiratory failure, where the lungs are unable to supply enough oxygen to the body. This may require hospitalization and supportive care such as oxygen therapy or mechanical ventilation. Hospitalized patients are often monitored closely for signs of dehydration, low oxygen levels, and secondary infections.
Secondary bacterial infections, such as acute otitis media (middle ear infection), sinusitis, or bacterial pneumonia, can occur as complications of RSV, particularly in young children. These infections often require antibiotic treatment, even though RSV itself is caused by a virus.
Increasing evidence suggests that severe RSV infection during infancy may have lasting effects on respiratory health. Studies have found that children who experienced serious RSV infections early in life have a higher risk of developing asthma, wheezing disorders, or airway hyperreactivity later in childhood. The exact cause of this association remains under study, but it is believed that early damage to the airway and immune system responses may play a role.
The table below summarizes key complications and associated risk factors:
| Complication | Risk Group | Severity |
| Bronchiolitis | Infants, elderly | Moderate to severe |
| Pneumonia | Infants, elderly, immunocompromised | Severe |
| Respiratory failure | Infants with chronic illnesses | Critical |
| Secondary infections | All ages, especially children | Mild to moderate |
Epidemiology and Global Impact
Respiratory Syncytial Virus (RSV) causes widespread illness, particularly among infants, young children, and older adults. It leads to significant rates of hospitalization and remains a leading cause of respiratory infections worldwide.
RSV Infection Statistics
RSV infects nearly all children by age two, with annual infection rates in infants often exceeding 60%. In the United States, RSV accounts for approximately 58,000 hospitalizations and 100-500 deaths annually among children under five. Globally, RSV is responsible for about 33 million lower respiratory tract infections each year, leading to nearly 3 million hospital admissions and over 100,000 deaths, predominantly in low- and middle-income countries.
Seasonal peaks occur in winter months in temperate climates, while year-round circulation is typical in tropical regions. Reinfections are common due to incomplete immunity after the first infection.
Economic Burden
RSV imposes significant economic costs related to medical care and lost productivity. In the U.S., the direct medical cost of RSV in children under five is estimated at $300 million annually, excluding parental work loss. Hospitalization accounts for the largest share of these costs.
Globally, resource-limited settings face increased strain due to severe cases requiring intensive care. Preventive measures and early intervention could reduce long-term burdens. Cost-effectiveness analyses support investment in vaccination and monoclonal antibody programs to lower future healthcare expenses.