As the world continues to navigate the evolving landscape of the COVID-19 pandemic, a new variant, NB.1.8.1, has emerged as a global concern. First identified in China, where it has driven a significant surge in cases and hospitalizations, this variant has now been detected in the United States, including major hubs like New York City. The Centers for Disease Control and Prevention (CDC) has confirmed its presence through airport screening programs, raising questions about its potential impact on public health. While early data suggest that NB.1.8.1 does not cause more severe illness than previous strains, its apparent increased transmissibility has prompted heightened vigilance from health authorities worldwide. This article explores the origins, characteristics, spread, and public health response to the NB.1.8.1 variant, offering a comprehensive look at what this development means for the U.S. and beyond.
The Emergence of NB.1.8.1: Origins and Global Context
A New Variant Emerges in Asia
The NB.1.8.1 variant, a descendant of the Omicron sublineage JN.1 and derived from the recombinant variant XDV.1.5.1, was first identified in China on January 22, 2025. By May 23, 2025, the World Health Organization (WHO) classified it as a Variant Under Monitoring (VUM) due to its rapid spread and increasing global prevalence. In China, NB.1.8.1 has become the dominant strain, contributing to a significant rise in COVID-19 cases, emergency room visits, and hospitalizations. Hong Kong authorities have reported that COVID-19 levels in the city have reached their worst point in at least a year, with a "significant increase" in reported hospitalizations. Similarly, Taiwan has noted a troubling uptick in severe cases and deaths, prompting health officials to stockpile vaccines and antiviral treatments.
The variant’s rapid spread in Asia, particularly in China, Hong Kong, Singapore, and Taiwan, has drawn international attention. Beyond Asia, cases have been reported in countries such as Japan, South Korea, France, Thailand, the Netherlands, Spain, Vietnam, Australia, and several European nations, including France, Germany, Ireland, and Sweden. This global dissemination underscores the interconnected nature of modern travel and the challenges of containing highly transmissible pathogens.
Detection in the United States
The NB.1.8.1 variant was first detected in the U.S. in late March and early April 2025, with the earliest cases identified in California and Washington state. The CDC’s airport screening program, conducted in partnership with Ginkgo Bioworks, identified multiple cases among international travelers arriving at major U.S. airports, including those in California, Washington, Virginia, and the New York City area. These cases, identified between April 22 and May 12, 2025, involved travelers from countries such as Japan, South Korea, France, Thailand, the Netherlands, Spain, Vietnam, China, and Taiwan, according to sequencing data published on the Global Initiative on Sharing All Influenza Data (GISAID) database.
In addition to airport detections, health authorities in states such as Ohio, Rhode Island, and Hawaii have reported community cases of NB.1.8.1, indicating that the variant has begun to spread beyond travelers. In New York, the state Health Department confirmed two cases of the variant, though it has not yet become widespread. The CDC notes that fewer than 20 sequences of NB.1.8.1 have been reported in U.S. baseline surveillance data, meaning it has not yet met the threshold for inclusion in the agency’s COVID Data Tracker dashboard. This limited prevalence suggests that the variant is not yet dominant in the U.S., but its detection in multiple states and among international travelers has raised concerns about its potential to spread further.
Characteristics of NB.1.8.1: What Makes It Different?
Transmissibility and Immune Evasion
Preliminary research indicates that NB.1.8.1 is more transmissible than some earlier variants, likely due to its enhanced ability to bind to human cells. This characteristic allows the virus to infect cells more efficiently, potentially leading to higher infection rates. However, early studies from researchers in China suggest that NB.1.8.1 does not significantly outperform other circulating strains in evading the immune system. This is a critical distinction, as immune evasion could reduce the effectiveness of existing vaccines and prior immunity from infections.
Dr. Amy Edwards, an assistant professor of pediatrics at Case Western Reserve University specializing in infectious diseases, noted that laboratory evidence supports the variant’s increased binding affinity to human cells, which contributes to its transmissibility. However, she emphasized that this does not necessarily translate to more severe infections. Subhash Verma, a professor of microbiology and immunology at the University of Nevada, Reno School of Medicine, added that NB.1.8.1 is associated with symptoms “broadly similar” to those of earlier strains, such as cough, fever, and fatigue.
Severity and Symptoms
Current data from Hong Kong, Taiwan, and other regions where NB.1.8.1 is prevalent indicate that the variant does not lead to more severe illness compared to other Omicron subvariants. The WHO has assessed the additional public health risk posed by NB.1.8.1 as low at the global level, stating that “current data do not indicate that this variant leads to more severe illness than other variants in circulation.” This is consistent with reports from Hong Kong, where authorities have found no evidence of increased severity despite a rise in hospitalizations.
The symptoms of NB.1.8.1 are reported to be similar to those of previous Omicron variants, including:
- Cough
- Fever
- Sore throat
- Fatigue
- Runny nose or nasal congestion
- Headache
- Muscle aches
These symptoms align with the typical presentation of COVID-19, and there have been no reports of unique or novel symptoms associated with NB.1.8.1. However, the variant’s increased transmissibility means that it could lead to more infections, which, even without increased severity, could strain healthcare systems if case numbers rise significantly.
Public Health Response in the United States
CDC’s Airport Screening ProgramThe CDC’s airport screening program, in collaboration with Ginkgo Bioworks, has been instrumental in detecting NB.1.8.1 cases among international travelers. The program involves testing and genomic sequencing of samples from arriving passengers at major U.S. airports, including those in California, Washington, Virginia, and New York City. The sequencing results, uploaded to the GISAID database, provide critical data on the variant’s global spread and its introduction into the U.S.
The detection of NB.1.8.1 through airport screenings highlights the importance of surveillance in tracking emerging variants. Dr. Steve Feagins, Hamilton County Public Health Medical Director in Cincinnati, emphasized that “surveillance is key” in monitoring the variant’s spread and understanding its potential impact. The CDC has stated that it is in regular contact with international partners to monitor the variant’s global prevalence and is maintaining close surveillance efforts in the U.S.
Community Surveillance and State-Level ResponseBeyond airport screenings, health authorities in states like Ohio, Rhode Island, and Hawaii have reported community cases of NB.1.8.1, indicating that the variant is circulating beyond travelers. In New York, the state Health Department is actively monitoring the variant, with two confirmed cases reported as of May 2025. The Wadsworth Center Laboratory, part of the New York State Department of Health, continues to sequence COVID-19 samples to track variants, contributing to a robust surveillance program that includes data from other laboratories across the state and nation.
The New York State Health Department has also noted that COVID-19 deaths in the state over the past year have ranged from a high of 73 per week in September 2024 to a low of 10 per week in December 2024. On Long Island, 68 patients are currently hospitalized with COVID-19, including seven in intensive care, reflecting the ongoing burden of the virus even as case rates remain relatively low.
Vaccine Updates and Recommendations
The emergence of NB.1.8.1 has sparked discussions about updating COVID-19 vaccines for the upcoming fall and winter seasons. The FDA’s vaccine advisory committee met in May 2025 to deliberate on which strains to target in the next round of vaccines. While last season’s vaccines targeted a JN.1 descendant called KP.2, early data from Pfizer and Moderna suggest that switching to a vaccine targeting LP.8.1, another JN.1 descendant dominant in the U.S., could provide cross-protection against NB.1.8.1. Darin Edwards, lead of Moderna’s COVID-19 program, told the panel that “the LP.8.1 vaccine has the highest titers against LP.8.1, which is dominant in the U.S. and many other regions and cross-neutralizes other currently circulating variants, including NB.1.8.1.”
The committee unanimously recommended updating vaccines to target a JN.1-based variant, though there was debate over whether to adopt the LP.8.1 formulation or retain last season’s vaccines. Some experts argued for maintaining the existing formulation, while others supported the update to enhance protection against emerging variants like NB.1.8.1. Jerry Weir, director of the FDA’s division of viral products, noted that while the virus’s evolution is unpredictable, “the overwhelming odds are that what does come and predominate in the next few months, the next six months, next year will come from something that’s circulating now.”
The WHO has stated that currently approved COVID-19 vaccines are expected to remain effective against NB.1.8.1 for preventing symptomatic and severe disease, providing reassurance that existing vaccines offer some level of protection. However, the Trump administration’s recent announcement to limit approval for seasonal COVID-19 shots to seniors and high-risk individuals has raised concerns about vaccine access. Dr. Céline Gounder, a CBS News medical contributor, warned that these restrictions could reduce access for some populations, potentially exacerbating the impact of new variants.
Global Response and Lessons from AsiaHong Kong and Taiwan: Masking and StockpilingIn Hong Kong, where NB.1.8.1 has driven a significant increase in cases, authorities have urged residents to wear masks in public transportation and crowded places. This recommendation aligns with evidence that masks are effective in preventing the spread of respiratory viruses, including COVID-19. Dr. Amy Edwards emphasized that masks are particularly effective for preventing infected individuals from transmitting the virus to others, stating, “If I’ve got a slight sore throat, little bit of sniffles, obviously, that might not be enough to keep me home, but if I put a mask on, I can reduce the risk that I would transmit whatever I’m carrying to other people.”
Taiwan has also responded proactively, stockpiling vaccines and antiviral treatments to prepare for potential surges. The rise in emergency room visits and deaths in Taiwan underscores the need for robust preparedness, even for variants that do not appear to be more severe. These measures highlight the importance of non-pharmaceutical interventions, such as masking, alongside pharmaceutical strategies like vaccination and treatment.
International Collaboration
The WHO’s designation of NB.1.8.1 as a Variant Under Monitoring reflects the global health community’s commitment to tracking emerging variants. The CDC’s collaboration with international partners and its use of the GISAID database demonstrate the importance of global data sharing in understanding and responding to new variants. The rapid dissemination of NB.1.8.1 across multiple continents underscores the need for coordinated surveillance and response efforts to prevent widespread outbreaks.
Implications for the United StatesSeasonal Patterns and Current TrendsThe CDC has noted that COVID-19 in the U.S. is settling into a more predictable seasonal pattern, with small spikes in summer and larger ones in winter. Current data indicate that COVID-19 rates in the U.S. are low, with cases and hospitalizations declining since the winter of 2024. However, the emergence of NB.1.8.1 and another variant, XFC, which is showing significant growth in the U.S., highlights the ongoing challenge of viral evolution. The CDC reports that COVID-19 has killed an average of 350 Americans per week over the past month, a significant decline from the peak of 25,974 weekly deaths in January 2021.
Despite the low case rates, experts caution that the virus’s unpredictability requires continued vigilance. Dr. Sharon Nachman, chief of pediatric infectious diseases at Stony Brook Children’s Hospital, noted that prior COVID-19 exposure, including vaccinations, continues to provide some level of protection against new variants. However, low vaccination uptake and waning immunity could contribute to higher death rates in some populations.
Public Health Recommendations
To protect against NB.1.8.1 and other circulating variants, health officials recommend the following measures:
- Monitor Symptoms: Seek medical advice if you develop symptoms, especially if you are at high risk for severe illness.
- Stay Home if Sick: If you experience symptoms like cough, fever, or sore throat, stay home to avoid spreading the virus.
- Practice Good Hygiene: Regular handwashing and avoiding contact with sick individuals can reduce transmission risk.
- Wear Masks in High-Risk Settings: Masks are recommended in crowded indoor spaces or on public transportation, especially in areas with rising cases.
- Stay Up to Date with Vaccinations: Ensure you have received the latest COVID-19 vaccines and booster shots, as they are expected to remain effective against NB.1.8.1.
These recommendations align with broader strategies to manage respiratory viruses and reflect lessons learned from previous waves of the pandemic.
Challenges and Controversies
Vaccine Policy Changes
The Trump administration’s decision to limit seasonal COVID-19 vaccine approvals to seniors and high-risk individuals has sparked debate. Critics, including Dr. Céline Gounder, argue that this policy could reduce access for younger, healthier individuals who may still benefit from vaccination, particularly in the context of new variants like NB.1.8.1. Health and Human Services Secretary Robert F. Kennedy Jr., who has expressed skepticism about vaccines, has emphasized transparency in vaccine policy, but the restrictions have raised concerns about potential gaps in protection.
Public Perception and Fatigue
Public sentiment, as reflected in posts on X, reveals a mix of concern, skepticism, and fatigue regarding the new variant. Some users express frustration with the ongoing emergence of variants, with comments like, “There’s been so many variants they’re not even giving them actual names. NB.1.8.1 sounds like a software update.” Others emphasize the need for continued precautions, with one user stating, “OH, boy. Let’s replenish my mask in my vehicle. Scary times.” These reactions highlight the challenge of maintaining public engagement with COVID-19 prevention measures five years into the pandemic.Looking Ahead: The Future of NB.1.8.1 in the U.S.While NB.1.8.1 has not yet become widespread in the U.S., its detection in multiple states and among international travelers suggests that it could gain traction, particularly as summer travel increases.
The variant’s increased transmissibility, combined with the potential for waning immunity and low vaccination uptake, could lead to localized surges if not addressed proactively. However, the lack of evidence for increased severity and the effectiveness of existing vaccines provide some reassurance.Health officials are closely monitoring NB.1.8.1 alongside other variants, such as XFC, to assess their impact on public health. The CDC’s ongoing surveillance efforts, combined with international collaboration and advances in vaccine development, will be critical in managing the spread of this variant. As Dr. Thornburg from the CDC noted, “After five years now, we are seeing very distinct patterns that [are] falling into a more predictable pattern,” suggesting that the U.S. is better equipped to handle new variants than in the early days of the pandemic.
Conclusion
The detection of the NB.1.8.1 variant in the United States marks another chapter in the ongoing COVID-19 pandemic. While the variant’s increased transmissibility is a cause for concern, its lack of increased severity and the effectiveness of existing vaccines offer hope that its impact can be mitigated. The CDC’s airport screening program, state-level surveillance, and global data-sharing efforts underscore the importance of proactive monitoring in addressing emerging variants. As the U.S. navigates this new challenge, public health measures like vaccination, masking, and good hygiene remain essential tools in preventing the spread of NB.1.8.1 and protecting vulnerable populations.For now, the public is encouraged to stay informed, follow health guidelines, and remain vigilant as the situation evolves. The lessons learned from previous variants and the robust surveillance systems in place provide a strong foundation for managing NB.1.8.1 and future variants. As the world continues to adapt to the ever-changing nature of COVID-19, collaboration, science, and preparedness will be key to keeping communities safe.