New COVID-19 Variant NB.1.8.1 Detected in the U.S. After Surge in China

A new COVID-19 variant, NB.1.8.1, has been identified in the United States following a significant increase in hospitalizations across China. This highly transmissible strain, a descendant of the Omicron lineage, was first detected among international travelers arriving at U.S. airports between late March and early April 2025. Subsequent cases have been reported in several states, including New York, California, Washington, Virginia, Ohio, Rhode Island, and Hawaii.

In China and Hong Kong, NB.1.8.1 has become the dominant strain, leading to a sharp increase in COVID-related hospitalizations and emergency room visits, particularly among older adults. For instance, Hong Kong reported 81 severe cases and 30 deaths linked to the variant within a four-week period, with most cases involving individuals aged 65 and above.

Despite its rapid spread, NB.1.8.1 does not appear to cause more severe illness than previous variants. Common symptoms include cough, sore throat, fever, and fatigue, similar to earlier strains. However, the variant's enhanced ability to bind to human cells may increase its transmissibility.

The World Health Organization (WHO) has designated NB.1.8.1 as a "variant under monitoring," indicating the need for prioritized attention and surveillance. Health experts advise continued vigilance, including staying up to date with vaccinations, practicing good hygiene, and wearing masks in crowded or enclosed spaces, especially for vulnerable populations.

In response to the emergence of NB.1.8.1, U.S. health authorities have updated COVID-19 vaccine guidance. The Centers for Disease Control and Prevention (CDC) now recommends booster doses primarily for high-risk groups, including the elderly and individuals with underlying medical conditions. Routine vaccination is no longer advised for healthy children and pregnant women.

While the number of NB.1.8.1 cases in the U.S. remains low, the situation underscores the importance of ongoing surveillance and adherence to public health measures to mitigate the spread of emerging COVID-19 variants.

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