Protective bubble around newborn in NICU, symbolizing RSV protection.

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

Beau Callahan in Health & Wellness July 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.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.jped.2018.10.014, Alternate LINK

Title: First Report Of Two Consecutive Respiratory Syncytial Virus Outbreaks By The Novel Genotypes On-1 And Na-2 In A Neonatal Intensive Care Unit

Subject: Pediatrics, Perinatology and Child Health

Journal: Jornal de Pediatria

Publisher: Elsevier BV

Authors: Daniella Gregoria Bomfim Prado Da Silva, Flávia Jacqueline Almeida, Mariana Volpe Arnoni, Marco Aurélio Palazzi Sáfadi, Marcelo Jenne Mimica, Daniel Jarovsky, Gabriela Pereira De Almeida Rossetti, Mauricio Magalhães, Danielle Bruna Leal De Oliveira, Luciano Matsumiya Thomazelli, Thais Cristina Colmanetti, Edison Luiz Durigon, Eitan Naaman Berezin

Published: 2020-03-01

Everything You Need To Know

What is Respiratory Syncytial Virus (RSV), and why is it a concern in Neonatal Intensive Care Units (NICUs)?

Respiratory Syncytial Virus (RSV) is a common virus that often presents with mild, cold-like symptoms. However, in infants, especially those born prematurely or with existing health conditions, RSV can cause serious respiratory illness. Neonatal Intensive Care Units (NICUs) are particularly susceptible to RSV outbreaks. This is due to the concentration of vulnerable, often premature, infants who have underdeveloped immune systems, making them highly susceptible to severe complications from RSV infection. These complications can lead to prolonged hospitalization and potentially life-threatening situations, emphasizing the critical need for strict infection control measures within NICUs.

What are the ON-1 and NA-2 genotypes of RSV, and how do they differ?

RSV is classified into two main types, A and B, with further classifications into different strains or genotypes. ON-1 and NA-2 are novel genotypes of RSV-A. These genotypes represent slight genetic variations within the RSV-A type. The ON-1 and NA-2 genotypes can influence how easily the virus spreads and the severity of the illness. As newer strains, infants may have little to no existing immunity, which can lead to more widespread outbreaks. The identification of specific genotypes like ON-1 and NA-2 is crucial for understanding the dynamics of RSV outbreaks and implementing effective control measures.

How do the ON-1 and NA-2 RSV genotypes impact the severity of the illness and transmission rates?

Novel genotypes like ON-1 and NA-2 may spread more easily due to a lack of pre-existing immunity among infants. This can result in higher transmission rates within the NICU environment. While the São Paulo study did not definitively prove that ON-1 or NA-2 caused more severe symptoms, it's recognized that some RSV genotypes can be associated with increased illness severity. The study highlights the importance of vigilant monitoring and rapid identification of RSV genotypes during outbreaks to inform infection control strategies and potentially influence treatment decisions. Because of their novelty, infants might not have developed prior immunity, leading to potentially more extensive outbreaks.

What measures can parents and caregivers take to protect their baby during an RSV outbreak in a NICU?

While RSV outbreaks in NICUs can be worrying, hospitals have strict protocols to minimize transmission and protect vulnerable infants. These include rigorous hand hygiene practices by all staff and visitors, cohorting infected infants to prevent the spread of the virus, and limiting visitation during outbreaks to reduce the number of potential exposures. Parents and caregivers should openly communicate with healthcare providers and ask any questions or express any concerns they have about their baby’s health. Staying informed and actively participating in your baby's care ensures your child’s safety.

Why is understanding RSV genotypes like ON-1 and NA-2 important in managing outbreaks in NICUs?

Understanding specific RSV genotypes, such as ON-1 and NA-2, is crucial for effective outbreak management in NICUs. Identifying the circulating genotype allows hospitals to implement targeted infection control strategies. This includes potentially adjusting treatment decisions and implementing measures to contain the spread more effectively. Monitoring genotypes helps healthcare providers understand the virus's behavior, predict the outbreak's course, and tailor interventions. The rapid identification of RSV genotypes contributes to better patient outcomes by allowing for prompt and appropriate responses to protect vulnerable newborns.