Protective bubble around newborn in NICU, symbolizing RSV protection.

Decoding RSV Outbreaks in Neonatal ICUs: What Parents Need to Know

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Beau Callahan in Health & Wellness May 2025 • 4 min read.

"A closer look at the ON-1 and NA-2 genotypes and how they impact your newborn's health during outbreaks."


Respiratory Syncytial Virus (RSV) is a common virus that usually causes mild, cold-like symptoms. However, for infants, especially those born prematurely or with underlying health conditions, RSV can lead to severe respiratory illness, requiring hospitalization. Neonatal intensive care units (NICUs) are particularly vulnerable to RSV outbreaks, posing a significant threat to these fragile patients.

A recent study published in the Jornal de Pediatria sheds light on two consecutive RSV outbreaks in a NICU in São Paulo, Brazil. What makes this study particularly important is that these outbreaks were caused by two novel genotypes of RSV, known as ON-1 and NA-2. Understanding these genotypes and how they spread is crucial for protecting your baby.

This article aims to break down the key findings of this study, providing you, as parents and caregivers, with the information you need to understand RSV outbreaks in NICUs, the risks involved, and the measures taken to control them. Knowledge is power, and being informed is the first step in advocating for your child's health.

What are ON-1 and NA-2 Genotypes, and Why Do They Matter?

Protective bubble around newborn in NICU, symbolizing RSV protection.

RSV is categorized into two main types: A and B. Within these types, there are different strains or genotypes, each with slight genetic variations. These variations can influence how easily the virus spreads and the severity of the illness it causes. The ON-1 and NA-2 genotypes are relatively new strains of RSV-A that have been identified in recent years.

The study in São Paulo found that the first outbreak was caused by the ON-1 genotype, while the second was caused by the NA-2 genotype. This highlights the dynamic nature of RSV and the importance of ongoing surveillance to identify emerging strains. Because these genotypes are relatively new, infants may have little to no immunity to them, potentially leading to more widespread outbreaks.

  • Higher Transmission Rates: Novel genotypes may spread more easily due to lack of pre-existing immunity.
  • Potential for Increased Severity: Some genotypes might be associated with more severe symptoms, although this wasn't definitively proven in the São Paulo study.
  • Impact on Outbreaks: Understanding the circulating genotypes helps hospitals implement targeted control measures.
The research underscores the need for vigilant monitoring and rapid identification of RSV genotypes during outbreaks to inform infection control strategies and potentially influence treatment decisions. The sooner hospitals can identify the specific strain of RSV, the better equipped they are to manage the outbreak and protect vulnerable newborns.

Protecting Your Baby: What You Can Do

While RSV outbreaks in NICUs can be concerning, hospitals have protocols in place to minimize the risk of transmission and protect vulnerable infants. The study from São Paulo reinforces the importance of these measures, including strict hand hygiene, cohorting infected infants, and limiting visitation during outbreaks. Remember to openly communicate with your healthcare providers with any questions or concerns regarding your baby’s health.

Everything You Need To Know

1

What is Respiratory Syncytial Virus (RSV), and why is it a concern in a NICU?

Respiratory Syncytial Virus (RSV) is a widespread virus, yet, for infants, especially those born prematurely or with underlying health conditions, it can result in severe respiratory illness, often necessitating hospitalization. Neonatal intensive care units (NICUs) are particularly susceptible to RSV outbreaks, which poses a significant threat to these fragile patients.

2

What are the ON-1 and NA-2 genotypes, and why are they significant in the context of RSV outbreaks?

The ON-1 and NA-2 genotypes are relatively new strains of RSV-A. Because these genotypes are novel, infants may have limited or no pre-existing immunity, potentially contributing to more extensive outbreaks. Understanding which RSV genotypes are circulating allows hospitals to implement targeted control measures to mitigate transmission. These measures are critical to protecting vulnerable newborns.

3

What role did the ON-1 and NA-2 genotypes play in the RSV outbreaks discussed?

In the context of the study in São Paulo, the ON-1 genotype caused the first outbreak, followed by the NA-2 genotype. This demonstrated the dynamic nature of RSV and the need for ongoing surveillance to identify emerging strains. Identifying the specific strain of RSV helps hospitals better manage the outbreak, protect vulnerable newborns, and informs treatment decisions.

4

How are different genotypes of RSV classified, and why is this distinction important?

RSV is categorized into two main types: A and B. Within these types, there are different strains or genotypes, each with slight genetic variations. These variations can influence how easily the virus spreads and the severity of the illness it causes. The study in São Paulo underscores the need for vigilant monitoring and rapid identification of RSV genotypes to inform infection control strategies.

5

What steps can parents and hospitals take to protect babies from RSV outbreaks in a NICU?

Hospitals utilize several measures to minimize the risk of transmission and protect vulnerable infants during an RSV outbreak in a Neonatal intensive care unit (NICU). These include strict hand hygiene, cohorting infected infants, and limiting visitation during outbreaks. Open communication with healthcare providers regarding your baby’s health is also essential.

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