The coronavirus (COVID-19) is back. Reports from health authorities around the world have detected a new highly contagious strain of the virus that has been spreading through Asia and has now reached Russia.

The virus never went away after first appearing in 2020, but subsequent variants have been less contagious or deadly than the original initial "wild-type" strain of SARS-CoV-2. The latest manifestation, a variant designated NB.1.8.1, is less lethal than that and health authorities have yet to pull the trigger on imposing public health protective measures. They say that most people will recover and only a small proportion will need hospitalisation, however, it is very contagious and now spreading fast.

NB.1.8.1 became the dominant strain across Japan, China, and Hong Kong, while now making its initial forays into the Americas and Europe, according to the latest reports.

Though the world has largely moved on from the chaos caused by the pandemic five years ago, this new variant serves as a stark reminder that SARS-CoV-2 could potentially cause further disruptions in the near future, should it mutate again.

bne IntelliNews staff in Moscow are down with the virus and have been self-isolating. Doctors in the Russian capital told bne IntelliNews staff that the virus spread is spreading and they worry it is getting to epidemic proportions. But there have been few fatalities and victims are being treated with regular off the shelf medication for viral infections. Doctors recommend victims to stay at home and take plenty of rest and liquids.

While the Russian outbreak means the virus has arrived in Europe, sanctions on Russia will slow down its spread. All direct flights between Moscow and the European capitals were cancelled three years ago following the invasion of Ukraine. Russian can still travel to Europe, but only through circuitous routes via Istanbul or Belgrade that are prohibitively expensive. Russian tourists have taken to holidaying in Asia since the start of the war and there have been no significant outbreaks in Western Europe as of the time of writing.

The epicentre of this latest outbreak lies firmly in East Asia. NB.1.8.1 is now the dominant COVID-19 strain in China, where it is contributing to spikes in emergency room visits and hospitalisations, whilst it was the dominant variant in Hong Kong and China at the end of April.

Hong Kong authorities report that COVID-19 levels are the worst in at least a year, following what officials describe as a "significant increase" in reported emergency room visits and hospitalisations driven by COVID-19 there as well. The severity of the situation has prompted Hong Kong health officials to issue public guidance urging residents to don masks on public transport and in crowded areas—a return to pandemic-era precautions that many hoped were consigned to history.

Health authorities in Taiwan have also reported a rise in emergency room visits, severe cases and deaths, whilst Taiwan has seen a rise in severe cases and deaths, prompting officials to stockpile vaccines and antiviral treatments in anticipation of further spread, the bne IntelliNews bureau in Taiwan reports.

Likewise, an outbreak has been reported in Singapore, with the number of confirmed cases doubling in a week from 16,000 to 33,000, according to the local health authorities.

The variant's international reach became apparent through genomic surveillance programmes. As of May 18, 518 NB.1.8.1 sequences were submitted to GISAID from 22 countries, representing 10.7% of the globally available sequences. This figure represents a significant rise from 2.5% four weeks prior, demonstrating the variant's rapid ascendancy.

America's airport screening programme, operated through the Centres for Disease Control and Prevention, has detected the variant amongst international travellers arriving from diverse origins. Cases linked to the NB.1.8.1 variant have been reported in arriving international travellers at airports in California, Washington state, Virginia and the New York City area, with infected passengers having departed from Japan, South Korea, France, Thailand, the Netherlands, Spain, Vietnam, China and Taiwan. Beyond these airport detections, cases of NB.1.8.1 have also now been reported by health authorities in other states, including Ohio, Rhode Island and Hawaii.

NB.1.8.1 is not a killer

NB.1.8.1 represents another evolutionary step in the Omicron lineage, descending from the recombinant XDV lineage. The variant carries the following additional spike mutations: T22N, F59S, G184S, A435S, V445H, and T478I compared to the currently dominant LP.8.1 strain.

These mutations appear to confer enhanced transmissibility, say doctors. There is some evidence in the lab that this variant binds more tightly to human cells, which means it is easier to transmit, according to infectious disease specialists.

As of now, there is limited publicly available data on the exact R₀ (basic reproduction number) of the NB.1.8.1 variant of coronavirus. NB.1.8.1 is a sub-lineage of Omicron and as such highly transmissible --  possibly among the most contagious of all SARS-CoV-2 variants to date.

Estimated R₀ for Omicron subvariants ranges from 8 to 12, according to data from public health agencies and modelling studies. However, NB.1.8.1 specifically has not had a distinct R₀ value published in peer-reviewed studies or by major public health organisations as of the time of writing.

The original strain of SARS-CoV-2 that emerged in Wuhan in late 2019 had an estimated R₀ of 2 to 3 – relatively low. That means each person infected with SARS-CoV-2 typically infected two to three other people in the absence of immunity or mitigation measures.

However, crucially, the WHO has not yet observed any evidence it causes more severe disease compared to other variants. In other words, it is not a killer.

The clinical presentation of NB.1.8.1 infections mirrors that of its predecessors. Common symptoms include sore throat, fatigue, fever, mild cough, muscle aches, and nasal congestion, with gastrointestinal symptoms may also occur in some cases.

Commonly reported symptoms include respiratory issues such as cough and sore throat, as well as systemic effects like fever and fatigue, confirmed by the bne IntelliNews staff in Moscow, who complain of aches and constant fatigue.

The consistency of symptoms across variants reflects the fundamental biology of SARS-CoV-2, even as the virus acquires mutations that enhance its fitness. Infectious disease experts emphasise that data indicates that NB.1.8.1 does not lead to more deadly respiratory problems the 2020 version caused. However, it appears to have a growth advantage over the earlier version, suggesting it may spread more easily.

The emergence of NB.1.8.1 coincides with significant shifts in American vaccine policy. The Trump administration has restricted access to updated COVID-19 vaccines, limiting them to those over 65 or with underlying medical conditions, whilst requiring extensive clinical trials for broader use. This policy change means that many Americans without underlying conditions, such as diabetes, the most vulnerable group, may not have access to updated shots this autumn.

Despite these restrictions, the WHO has noted that current COVID-19 vaccines should still protect against severe disease caused by this variant. Vaccine manufacturers Pfizer and Moderna have presented data suggesting that vaccines targeting the LP.8.1 lineage can be considered as a suitable alternative and may offer cross-protection against NB.1.8.1.

The timing of this outbreak aligns with established patterns of COVID-19 circulation. The U.S. has historically seen COVID cases spike twice during the calendar year — once in the winter and again in the summer months — and 2025 should be no exception. Recent increases in SARS-CoV-2 activity are broadly consistent with levels observed during the same period last year, though global surveillance capacity remains limited.

The World Health Organisation's assessment suggests this represents part of the virus's natural evolution rather than a dramatic shift in pandemic dynamics.

Since mid-February 2025, according to data available from sentinel sites, global SARS-CoV-2 activity has been increasing, with the test positivity rate reaching 11%, levels that have not been observed since July 2024.

Public health officials worldwide are adopting a pragmatic approach to the emergence of NB. 1.8.1. Unlike the early days of the pandemic, when each new variant sparked widespread alarm, the response this time has been notably restrained. Governments are not reimposing lockdowns or widespread restrictions, recognising both the variant's limited severity and the public's pandemic fatigue.

Yet this measured response should not be mistaken for indifference. Health systems are quietly preparing for increased caseloads, with Hong Kong already experiencing strain in its emergency departments.

The variant's enhanced transmissibility means more infections are inevitable, and even if the proportion requiring hospitalisation remains unchanged, absolute numbers may rise significantly. The real test will come in the Northern Hemisphere's autumn, when respiratory viruses traditionally flourish. If NB.1.8.1 establishes itself as the dominant strain by then, health services could face renewed pressure just as seasonal influenza returns.