Xiao Ma, only two months old, was recently hospitalized due to a respiratory syncytial virus infection. It started with just one or two coughs, but three days later, wheezing and tachypnea developed, with a respiratory rate reaching over 60 breaths per minute and a heart rate soaring to 180-190 beats per minute (far exceeding the normal range for infants of the same age). Seeing their once healthy baby become so severely ill, the parents were filled with worry. Later, through pathogen-targeted sequencing, the culprit was identified: respiratory syncytial virus.
Recently, the pediatric inpatient unit has indeed admitted many children infected with this virus. Parents often ask: What exactly is this virus? Is it serious?
Today, let us discuss this in detail.
Not a Strange Virus, It Is Actually Very Common!
Respiratory syncytial virus (RSV) is a single-stranded, negative-sense RNA virus belonging to the Pneumoviridae family. It can cause acute respiratory infections in people of all ages, with children under 5 years being the most susceptible group. Statistics show that nearly all children have been infected with RSV by the age of 2.
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Not a New Virus, But It Arrives Annually "As Scheduled"
RSV exhibits seasonal outbreak characteristics globally. In the Northern Hemisphere, it typically becomes active from October or November, lasting until April or May of the following year, with peaks often occurring in January or February.
Northern China follows this pattern, while in some southern regions such as Guangdong, Fujian, Guangxi, Yunnan, Hainan, Taiwan, Hong Kong, and Macau, due to the warmer climate, the seasonal characteristics of RSV are less pronounced, exhibiting year-round endemicity.
Prone to Recurrent Infection, Immunity Is Not Durable
After RSV infection, the body does not acquire lasting immunity, and recurrent infections can still occur. RSV is divided into two subtypes, A and B, with subtype A typically causing more severe symptoms.
Each subtype contains multiple genotypes, and the predominant circulating strain may shift annually, which is why we are prone to being "repeatedly targeted." Generally, the first infection is most likely to cause severe lower respiratory tract disease; subsequent infections tend to be milder.
How Is It Transmitted?
RSV is primarily transmitted through contact with virus-containing secretions or contaminated objects, especially via hand contact with the mouth, nose, or eye mucosa. Direct contact is the most common mode of transmission, but droplets and aerosols can also contribute to spread.
The virus can survive on hands and surfaces for several hours, so frequent handwashing and isolation precautions are key to prevention.
Studies have also found that infant infections most commonly occur following infection in a family member.
#1
Symptoms Vary by Individual, Extra Caution Needed for Infants
RSV first replicates in the nasopharynx, then spreads downward to the bronchioles and alveoli, typically developing into bronchiolitis or pneumonia 1-3 days after infection, which can lead to hypoxia or even respiratory failure in severe cases.
Manifestations vary among different individuals after infection:
Older children: Often present with common cold symptoms such as cough, nasal congestion, rhinorrhea, and conjunctivitis. Compared to other viruses, RSV is more likely to cause sinusitis and otitis media.
Children under 2 years: More prone to lower respiratory tract infections, such as fever, cough, wheezing, and tachypnea.
Infants under 2 months, especially preterm infants: May present with apnea.
An international multicenter case-control study found that among children under 5 years hospitalized for severe pneumonia in Africa and Asia, RSV was the most frequently detected pathogen.
#2
Which Children Are More Likely to Develop Severe Disease
The following infants are at higher risk and experience more severe symptoms after RSV infection:
Infants under 6 months of age
Preterm infants
Those with congenital heart or lung disease, Down syndrome, or neuromuscular disorders
Immunocompromised individuals
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Furthermore, RSV infection during infancy may increase the risk of recurrent wheezing and even asthma later in life.
#3
Is There a Specific Antiviral?
Currently, there is no specific antiviral drug for RSV. Clinical treatment primarily focuses on symptomatic and supportive care, such as oxygen therapy, nebulized inhalation, and fluid replacement, to help the child safely navigate the infection period.
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#4
So, What Can Parents Do?
Basic Prevention
Frequent handwashing, especially before and after contact with the baby; proper hand hygiene is the most effective means of interrupting transmission.
Regular ventilation, maintain indoor air circulation, and avoid tobacco and other smoke irritation.
Cough etiquette, family members with colds should wear masks and practice appropriate isolation.
Avoid crowded places, during the RSV season, try to avoid taking high-risk infants to crowded areas.
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Specific Prophylaxis - Nirsevimab
Nirsevimab is a long-acting monoclonal antibody that precisely targets the RSV virus. Clinical data show that this drug demonstrates good efficacy in reducing the rates of medical visits, hospitalizations, and severe disease risk associated with RSV-related lower respiratory tract infections in infants, with protective effects lasting at least 5 months.
According to the World Health Organization's 2025 position paper, in areas with seasonal RSV epidemics, it is recommended to administer nirsevimab to infants before or during the epidemic season. In areas with year-round endemicity, a year-round immunization strategy is recommended, with vaccination as early as possible after birth.
China's National Medical Products Administration has approved nirsevimab for neonates and infants (under 1 year) who are about to enter or are born during their first RSV season:
· Body weight <5 kg: Single intramuscular injection of 50 mg
· Body weight ≥5 kg: Single intramuscular injection of 100 mg
It is a passive immunization agent that does not interfere with the active immune effects of routine vaccinations and can be administered concurrently with other childhood vaccines, with a good safety profile.
In conclusion, although RSV is common, it is not unpreventable. Scientific prevention measures combined with timely medical support are powerful tools to protect our babies from severe disease. We hope every baby can safely navigate each epidemic season and grow up healthy and happy!
Author of this article>>> Heyou Pinnacle Medical Center General Practice | Tang Haiting (Deputy Chief Physician)
Reviewer of this article>>> HeYou Hospital Pediatrics | Li Hong (Chief Physician)
(Due to individual patient differences, treatment outcomes may vary. Please consult a professional physician for specific advice.)
