It is nearly 80 months since the Novel Coronavirus, Severe Acute Respiratory Syndrome – Coronavirus Two (SARS-CoV-2), first burst onto the global scene. It proceeded to cause the devastating global Covid pandemic and in the early weeks and months, the harmful effects of this virus were both serious and dire. With refinements in management protocols of SARS-CoV-2 infected persons, the use of social distancing and the availability of effective and efficient Covid vaccines, this pandemic was finally brought under control. That the original virus mutated to one causing less severe disease (although it became a more transmissible form), helped with gaining control of this pandemic and the return of humanity to pre-Covid-type activities. During the past 24 months, newer SARS-CoV-2 variants have arisen intermittently, leading to small spikes in disease incidence, in specific regions of the world.

At the start of this year, it seemed that the world had learnt to live with Covid; with Covid vaccination being targeted to those at high risk of severe disease. In recent weeks, there have been reports of a rise in cases of Covid due to the SARS-CoV-2, NB.1.8.1 variant. The increase in cases initially occurred in Hong Kong and Singapore, but is now observed in several countries around the world. 

What is the NB.1.8.1 variant?

NB.1.8.1 is a SARS-CoV-2 variant that is derived from a recombinant variant called DV.1.5.1. It is a sub-lineage of the Omicron variant. Recombinant refers to the situation where a new variant arises following the genetic mixing of two or more existing variants. The NB.1.8.1 variant was first detected in samples collected in January. The World Health Organisation has classified it as a ‘variant under monitoring (VUM)’, owing to its rapid global spread. This variant is spreading at a much faster rate than the other currently circulating SARS-CoV-2 variants. By late April, it comprised roughly 10.7% of all submitted SARS-CoV-2 sequences. In comparison, four weeks before that, it was 2.5%. This variant has become the dominant strain in Hong Kong and China. It has also been detected in the United Kingdom, the United States of America, Australia and several tourist hotspots.

Transmissibility

When compared to the currently dominant (LP.8.1) SARS-CoV-2 variant, the NB.1.8.1 variant has some additional mutations (T22N, F59S, G184S, A435S, V445H and T478I) affecting the spike protein. The spike protein is found on the surface of the SARS-Cov-2 and allows the virus to infect cells via the human Angiotensin Converting Enzyme 2 (hACE2) receptor. The NB.1.8.1 variant is more transmissible than prior ones. The 445 mutation enhances binding to the hACE2 receptor on cells and thus increases transmissibility. Mutations at position 435 and 478 have been shown to reduce the neutralisation potential and enhance the evasion of some anti-SARS-CoV-2 antibodies.  

Clinical features and severity

Currently, there is no suggestion that the NB.1.8.1 variant causes more severe disease. Most infections due to this variant have been mild. The number of patients attending outpatient clinics has increased and so have hospital admissions in some countries. However, intensive care unit admissions have not shown any significant increases. In the past, the loss of the sense of taste and smell, were hallmark features of Covid (and this feature was more prominent early in the Covid pandemic). Reports suggest that many patients with Covid due to the NB.1.8.1 variant, develop fever, body aches, headache, hoarseness, throat discomfort, dry and irritating cough, and tiredness. Some patients also develop gastrointestinal symptoms such as nausea, heartburn, abdominal bloating, abdominal pain, vomiting and diarrhoea. 

Diagnosis 

With several parts of Sri Lanka experiencing monsoon showers, increased amounts of the standard and usual respiratory viral infections are bound to occur. Patients getting such infections may develop symptoms that overlap those caused by Covid. Thus, a high degree of awareness must be had by healthcare personnel and if a person develops some of the symptoms listed above, appropriate Covid testing needs to be considered.

Prevention and control 

The main Covid vaccines in current use continue to be able to provide protection against severe disease. The most recent vaccine booster targets the SARS-CoV-2, JN.1 variant, from which NB.1.8.1 is descended. As the new variant is part of the Omicron family, immunity from recent Covid infections should also provide protection against severe disease. Persons with weak immune systems (either due to immunodeficiency disorders or secondary to the use of immunosuppressive medicines for treating inflammatory, autoimmune or allergy-related diseases), those with multiple underlying health conditions and the elderly, should take additional precautions. They should strongly consider wearing masks in crowded places. If a person has symptoms of Covid, they should remain at home until (at least) 48 hours, after their symptoms have mostly or fully disappeared. They should specifically avoid contact with those who are at a higher risk.

Conclusions

Currently, countries around the world are monitoring both global and local trends in Covid infections, so as to institute (and possibly escalate) any appropriate and relevant control measures. 

(The writer is the President of the United Kingdom-Sri Lanka Immunology Foundation)

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The views and opinions expressed in this article are those of the author, and do not necessarily reflect those of this publication