The newly identified SARS-CoV-2 variant, NB.1.8.1, is an Omicron-descendent lineage derived from the recombinant variant XDV.1.5.1. It was first detected in January 2025 in Asia, and was designated a variant under monitoring (VUM) by the World Health Organization (WHO) on 23 May 2025. The NB.1.8.1 variant is increasing in prevalence globally, from 2.5% of sequences submitted to the Global Initiative on Sharing All Influenza Data (GISAID) in epidemiological week 14 of 2025 (31 March to 6 April 2025) to 10.7% in epidemiological week 17 of 2025 (21 to 27 April 2025). As of 18 May 2025, it has been detected in 22 countries, and has been associated with an increase in SARS-CoV-2 infections in parts of Asia.
Preliminary data indicate that the NB.1.8.1 variant has mutations in the spike protein that may increase the variant’s transmissibility and that result in marginal immune evasion compared to other currently circulating variants, such as LP.8.1. However, current data do not indicate that the NB.1.8.1 variant is associated with increased severity or different symptoms compared to other circulating lineages. As of 23 May 2025, the WHO considered the public health risk of NB.1.8.1 to be low. Current COVID-19 vaccines are expected to provide protection against severe illness due to NB.1.8.1 infections.
As of 10 June 2025, the NB.1.8.1 variant has not been detected in South Africa, although SARS-CoV-2 testing throughout the country is limited and few specimens are being submitted for sequencing. Data from the NICD’s respiratory illness syndromic surveillance programmes, which operate in selected public and private hospitals and outpatient facilities, show that the number of SARS-CoV-2 infections is currently low.
Currently, South Africa is seeing an increase in influenza cases due to the winter season. Individuals who are unwell with respiratory symptoms should practice regular hand washing, cover coughs and sneezes, and avoid contact with people who may be at high risk of severe respiratory illness. The public is reminded to practice hand and respiratory hygiene (cover coughs and sneezes). Monitoring of SARS-CoV-2 variants continues as part of national syndromic surveillance for respiratory illness and the Network for Genomic Surveillance in South Africa (NGS-SA).
Update: New COVID-19 variant NB.1.8.1 detected in Ekurhuleni wastewater; surveillance and testing ongoing
The new COVID-19 variant known as Nimbus or NB.1.8.1 has been detected in a wastewater surveillance sample collected on the 3rd June in the City of Ekurhuleni, Gauteng Province. Testing and sequencing with more recent wastewater samples is ongoing. Details may be found on the NICD SARS-CoV-2 dashboard at (https://wastewater.nicd.ac.za/). SARS-CoV-2 continues to cause very few outpatient or inpatient respiratory illnesses and testing rates amongst the general population remain low. To date, the NICD has not detected this lineage through our sentinel syndromic surveillance systems. However, global experience has shown that wastewater surveillance is able to detect new variants in communities before clinical surveillance confirms their presence.
Whilst NB.1.8.1 has been designated a SARS-CoV-2 variant under monitoring by global health authorities, newer variants of SARS-CoV-2 are continually replacing older ones, as viral mutation leads to immune escape. It is not unexpected to find NB.1.8.1 in South Africa, as travel and trade between countries and affected areas allows ongoing importation and transmission of infectious agents.
The severity of the NB.1.8.1 variant in South Africa is presently unknown. High levels of immunity to SARS-CoV-2 exist in South Africa which may lead to a less severe course of disease in infected persons.
During the winter season, preventing spread of respiratory illnesses including influenza, RSV and SARS-CoV-2 remains important. The public are advised to continue with good hand hygiene practices, covering the mouth when coughing and maintain distance from others when ill. When appropriate, ill persons may wear a mask, especially around individuals at higher risk of severe disease.
