According to the city’s Department of Health, genome sequencing conducted by the Hospital for Tropical Diseases in collaboration with the Oxford University Clinical Research Unit (OUCRU) found that six out of eight COVID-19 patients hospitalized in the third week of May were infected with NB.1.8.1, accounting for 83% of cases.
NB.1.8.1 is a descendant of the XDV.1 lineage, which emerged from a recombination of JN.1 and XDE variants. Its genome was first sequenced in early 2025, and as of May 22, the variant had been reported in at least 22 countries.
The World Health Organization (WHO) has not yet classified NB.1.8.1 as a variant under monitoring (VUM), a variant of interest (VOI), or a variant of concern (VOC), as there is currently no scientific evidence that it spreads faster or causes more severe illness than other circulating strains.
In Taiwan (China), NB.1.8.1 is currently dominant, with severe cases mostly found among the elderly, people with underlying health conditions, or those who are unvaccinated. The US Centers for Disease Control and Prevention (CDC) has also identified NB.1.8.1 in numerous samples collected from international travelers arriving at major airports. CBS News reported that the variant may be contributing to rising case numbers in China and some parts of Asia.
In Ho Chi Minh City, COVID-19 cases have been on the rise from weeks 16 to 20 of 2025 (April 14 to May 18), averaging 11 cases per week. This contrasts with just one to two cases per week during the first 15 weeks of the year. In week 20 alone, 26 new cases were recorded, bringing the year’s total to 79, down 75.5% compared to the same period in 2024. Of these, 43 patients required hospitalization while 36 were treated as outpatients. No cases required respiratory support.
Health authorities believe the emergence of NB.1.8.1 may be a factor behind the recent rise in infections, as seen in several other countries following the appearance of new variants. The Department of Health has instructed the Ho Chi Minh City Center for Disease Control (HCDC) to step up surveillance of the outbreak and SARS-CoV-2 variants, and has directed medical facilities to prepare appropriate admission and treatment plans based on the evolving situation.