A new COVID-19 variant, known as NB.1.8.1, has emerged as a growing concern after being linked to a surge in cases across Asia, particularly in China. The World Health Organization (WHO) has issued a warning about its rapid global spread, and early cases have now been detected in the United States. While the variant does not appear to cause more severe illness, its high transmissibility has health officials on alert. This article explores what we know about NB.1.8.1, its impact in the U.S., and what Americans should do to stay safe.
The NB.1.8.1 variant is a descendant of the Omicron subvariant JN.1, which has been a dominant strain in recent years. First identified in China in January 2025, NB.1.8.1 has since spread to at least 22 countries, with over 518 cases reported globally by mid-May, according to data from the Global Initiative on Sharing All Influenza Data (GISAID). The variant has a growth advantage, meaning it spreads more easily than other circulating strains, likely due to its enhanced ability to bind to human cells.
In the U.S., the Centers for Disease Control and Prevention (CDC) confirmed the presence of NB.1.8.1 in late March and early April, primarily among international travelers arriving at airports in California, Washington State, Virginia, and New York. Additional cases have been reported in Ohio, Rhode Island, Hawaii, and Arizona, indicating that the variant is now spreading locally. As of May 27, fewer than 20 cases had been detected in the U.S., but experts warn that its rapid spread in Asia could signal a potential wave of infections if precautions are not taken.
Dr. William Schaffner, a professor at Vanderbilt University School of Medicine, noted that NB.1.8.1 is “kind of scattered about the U.S. at the moment, in small numbers” and appears to be part of the Omicron family. While its presence is limited for now, its transmissibility is a cause for concern.
The rapid spread of NB.1.8.1 in Asia, particularly in China, Hong Kong, and Taiwan, has raised alarm bells. In China, the percentage of severely ill respiratory patients testing positive for COVID-19 has doubled from 3.3% to 6.3% in recent weeks, and emergency room visits for the virus have surged from 7.5% to 16.2%. Taiwan has reported a 78% increase in hospital admissions due to COVID-19, while Hong Kong has seen hospitalizations reach a 12-month high, prompting authorities to urge mask-wearing in public spaces.
Experts attribute the variant’s spread to its higher transmissibility compared to other strains. Subhash Verma, a professor of microbiology and immunology at the University of Nevada, Reno, explained, “Data indicates that NB.1.8.1 does not lead to more severe illness compared to previous variants, although it appears to have a growth advantage, suggesting it may spread more easily.” This ability to spread quickly could lead to a rise in cases and hospitalizations if public health measures are not followed.
Despite its spread, the WHO has classified NB.1.8.1 as a Variant Under Monitoring (VUM), not a Variant of Concern (VOC) or Variant of Interest (VOI). This means that while it is being closely watched, it is not yet considered a major threat to public health. The WHO has also stated that current data does not indicate that NB.1.8.1 causes more severe illness than other variants, offering some reassurance.
The symptoms of NB.1.8.1 are similar to those of previous Omicron variants, making it difficult to distinguish without testing. Common symptoms include:
Other reported symptoms may include nausea, loss of appetite, and gastrointestinal issues. Dr. Schaffner emphasized that these symptoms are generally mild, particularly for those who have been vaccinated or previously infected. However, high-risk groups, such as the elderly or those with underlying health conditions, may experience more severe symptoms.
One piece of good news is that current COVID-19 vaccines are expected to remain effective against NB.1.8.1. The WHO has stated that approved vaccines, including the 2024-2025 Moderna, Pfizer-BioNTech, and Novavax vaccines, should provide protection against severe disease caused by this variant. The CDC recommends that everyone over the age of six months receive the updated 2024-2025 COVID-19 vaccine, which targets strains related to JN.1.
However, there are concerns about vaccine efficacy. Dr. Edwin Tsui, head of Hong Kong’s Centre for Health Protection, warned of “early signs of vaccine mismatch” with NB.1.8.1, suggesting that the variant may partially evade immune responses in some cases. Despite this, the high level of immunity in the U.S. population—over 95% of Americans have either been vaccinated or previously infected—provides a strong defense against severe outcomes.
The U.S. Food and Drug Administration (FDA) has also taken steps to ensure vaccines remain effective. In May 2025, FDA advisers unanimously recommended that COVID-19 vaccines for the 2025-2026 season target newer strains of the JN.1 variant, including NB.1.8.1. This decision aims to keep vaccines aligned with circulating strains.
The emergence of NB.1.8.1 comes at a time when the U.S. is adjusting its COVID-19 vaccine policies. The Trump administration has announced plans to limit booster shots to high-risk groups, such as seniors, and has stopped recommending routine vaccinations for healthy children and pregnant women. The CDC updated its guidance on May 27, reflecting these changes. This shift has sparked debate, with some experts warning that limiting vaccine access could leave vulnerable populations at risk, especially as new variants like NB.1.8.1 emerge.
The FDA is also requiring manufacturers to conduct clinical trials to demonstrate the benefits of vaccines for healthy younger adults and children, a move that could further restrict access. Critics argue that this could increase the risk of mild or moderate illness and the spread of the virus to high-risk individuals, such as older relatives.
While NB.1.8.1 is not currently causing a surge in U.S. cases, health experts urge caution. The CDC reports that emergency room visits for COVID-19 remain low, and wastewater testing indicates minimal virus levels in most states. However, the variant’s rapid spread in Asia suggests that Americans should remain vigilant. Here are some steps to stay safe:
The emergence of NB.1.8.1 serves as a reminder that COVID-19 continues to evolve, requiring ongoing vigilance. While the variant does not appear to cause more severe illness, its ability to spread quickly could lead to increased cases and hospitalizations if not addressed. The U.S. is in a strong position due to high population immunity and effective vaccines, but changes in vaccine policy and waning booster uptake could pose challenges.
As the WHO and CDC continue to monitor NB.1.8.1, Americans are encouraged to stay proactive. By staying vaccinated, practicing good hygiene, and following public health guidance, we can help prevent another wave of infections. For the latest updates, visit the CDC’s COVID-19 page or the WHO’s global health updates.
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