Vigilance, Not Panic: Understanding the Emerging COVID-19 Variant NB.1.8.1

The recent detection of the SARS-CoV-2 variants NB.1.8.1 and LF.7 in India has led to public concern, especially as cases rise across parts of Southeast Asia. However, it is important to assess this development with evidence-based reasoning. As the pandemic evolves, the appearance of new viral lineages demands attention due to their chances of transmission, severity of infection, vaccine effectiveness, and the burden of long-term complications following infection [1-3]. 

A study from the Indian SARS-CoV-2 Genomics Consortium (INSACOG), NB.1.8.1 was detected in Tamil Nadu in April 2025, while four cases of LF.7 were identified in Gujarat in May. Both are subvariants of Omicron, likely deriving from the currently dominant JN.1 lineage. Recent reports indicate that JN.1 comprises over half (53%) of sequenced SARS-CoV-2 samples in India, followed by BA.2-related variants (26%) and other Omicron sublineages (20%) [4]. 

As of May 23, 2025, the WHO has categorised NB.1.8.1 and LF.7 as Variants Under Monitoring (VUM), suggesting it may possess notable genetic changes but do not yet demonstrate a clear epidemiological impact [5]. Early data from the WHO suggests that NB.1.8.1 poses a low to intermediate public health risk. While it carries spike mutations (A435S, V445H, T478I) which might be associated with increased transmission and immune evasion, current evidence does not indicate greater severity compared to previous variants [6]. 

Several states have reported recent increases in COVID-19 cases. For instance, in May 2025, Delhi reported 23 new cases, Andhra Pradesh four, and Telangana one. Bengaluru registered a positive case in a nine-month-old child. Kerala reported 273 new infections during the same month [7,8]. Despite these numbers, most infections appear mild. Clinicians such as Dr. Aviral Mathur and Dr. Dhruv Chauhan have stated that the dominant strain, JN.1, is generally associated with mild symptoms and does not warrant panic, though adherence to standard hygiene practices remains advisable [9,10]. 

In the United States, NB.1.8 has also been identified. Experts from the CDC and FDA, including Drs. Natalie Thornburg and Jerry Weir, have noted that SARS-CoV-2 now appears to exhibit seasonal fluctuations, with new dominant variants often emerging from existing lineages [11-13].

NB.1.8.1 is a sublineage of Omicron BA.2.86 and contains several spike protein mutations. Of particular note are changes in the RBD that influence interaction with the ACE2 receptor and neutralising antibodies [14,15]. Notable mutations include F486P, E484K, and N501Y were previously linked to increased binding affinity and immune evasion in earlier variants [16]. 

The emergence of NB.1.8.1 is part of a broader trend observed with other Omicron sublineages, such as LB.1 (also called the "FLiRT" variant), which saw a spike in emergency department visits in early 2024 [17]. NB.1.8.1 evolved from XDV 1.5.1 and features additional spike protein mutations compared to LP 8.1 and JN.1 [18]. Preliminary studies from China suggest NB.1.8.1 exhibits enhanced binding affinity to cells, which may contribute to its higher transmissibility [19]. 

Although not classified as a Variant of Concern (VOC), the variant’s ability to partially escape immunity, particularly in those with older vaccine-induced protection, is a matter for ongoing study. Enhanced genomic surveillance remains critical [4].

Current reports suggest that symptoms of NB.1.8.1 largely resemble previous Omicron infections, with mild respiratory complaints like sore throat, nasal congestion, mild fever, fatigue, and occasional gastrointestinal issues such as nausea or mild diarrhoea [20-25]. Loss of smell and taste has become less common. These symptoms have been predominantly mild, especially in individuals with prior infections or vaccination [26-29]. 

No significant increase in hospitalisations or mortality has been attributed to NB.1.8.1 or LF.7. Nevertheless, older adults, those with chronic conditions, and immunocompromised individuals remain vulnerable. The variant’s potential to escape immune responses may reduce the effectiveness of older vaccine-induced immunity [30,31].

At present, NB.1.8.1 does not appear to cause serious disease like earlier Omicron strains. Hospitalisation rates remain low. However, widespread transmission could increase total case numbers, indirectly leading to more hospital admissions. Coinciding respiratory infections and low booster coverage may further strain healthcare systems [2,32-35]. 

India’s public health infrastructure, including the Integrated Disease Surveillance Programme (IDSP) and the Indian Council of Medical Research (ICMR), has maintained active monitoring. The Directorate General of Health Services has reported no need for hospitalisation in most current cases [36,37]. States like Delhi have issued advisories to ensure hospital readiness and emphasised continued testing, isolation, and genome sequencing [38].

RT-PCR remains the most reliable test for COVID-19 diagnosis. Most commercial assays can detect NB.1.8.1 as it does not exhibit deletions in commonly targeted genomic regions. While rapid antigen tests are still in use, their sensitivity is variable. Broader sequencing, especially in clinical clusters and among international travellers, is necessary for tracking variant spread [39,40].

Fundamental prevention measures continue to be relevant: mask-wearing in closed or crowded spaces, regular hand hygiene, and isolating when symptomatic. States are advised to maintain screening and isolation protocols, particularly in institutions and transport hubs [41-47].

India’s population exhibits variable immunity. Some individuals have hybrid immunity (infection plus vaccination), while others may have waning protection due to time since last dose or infection [48-51]. Reinfections are expected, particularly among those previously infected with pre-Omicron strains. T-cell-mediated immunity remains relatively preserved, even as antibody levels decline [52-55]. 

While memory B-cell responses to Omicron have diminished, T-cell responses across CD4+ and CD8+ subsets remain robust. This may protect against severe outcomes despite reduced neutralising antibody levels [54-57].

India has achieved high coverage for primary and first booster doses, but uptake of the second booster, particularly among the elderly, is lower [58,59]. Studies indicate that vaccines such as Covishield and Covaxin continue to protect against severe illness, though their ability to prevent infection is reduced due to ongoing mutations [60-62]. Updated mRNA vaccines and nasal formulations tailored to Omicron sublineages may offer additional benefits [63-65]. Adaptive policy responses, including flexible booster schedules and improved surveillance, should be prioritised [66,67]. Vaccination has played a critical role in decreasing the hospital stay and long COVID [68-70]. 

The NB.1.8.1 variant is another reminder that SARS-CoV-2 continues to evolve. Although current data does not suggest a significant public health threat, continuous monitoring is essential [71]. Strengthened genomic surveillance, updated vaccines, and renewed emphasis on preventive measures will be key to managing its spread. While no immediate cause for alarm exists, appropriate preparedness grounded in scientific evidence remains essential for mitigating the impact of future surges.

As India reports fresh cases of the new COVID-19 variant NB.1.8.1, the public health narrative again finds itself at a familiar crossroads by balancing vigilance with preparedness. This variant, marked by mutations that may enhance immune escape and mimic symptoms of earlier strains, explains the ongoing mutation of this virus under immune and environmental pressures. While the threat level remains moderate, complacency could prove detrimental. 

A science-driven, proactive approach is essential. Strengthening genomic surveillance linked to clinical outcomes, reinstating masking and testing in high-risk areas, and expediting booster vaccinations, especially for vulnerable groups, is critical. Rapid approval and deployment of updated vaccines targeting new variants must be prioritised. Simultaneously, consistent public health messaging and community adherence to COVID-appropriate behaviour remain key. This evolving situation calls not for panic but for preparedness, guided by scientific vigilance and coordinated action across healthcare, policy, and public domains.

We declare if data is being shared, we shall provide the data.

No conflict of interest declared.

Nil

All authors state that they contributed to this publication according to the guidelines of the journal and that no part of this manuscript was plagiarized.

1. This material is the authors’ original work, which has not been previously published elsewhere.
2. The paper is not currently being considered for publication elsewhere.
3. The paper reflects the authors’ research and analysis truthfully and completely.
4. The paper properly credits the meaningful contributions of co-authors and co-researchers.
5. The results are appropriately placed in the context of prior and existing research.
6. All sources used are properly disclosed (correct citation). Copying of text must be indicated as such by using quotation marks and giving proper reference.

1. The Times of India (2025) TOI News Desk. The Times of India, India.
2. Aden D, Zaheer S, Kumar R, Raj S, Khan T, et al. (2022) Beyond COVID-19 and SARS-CoV-2, cardiovascular outcomes of "long COVID" from a pathological perspective - a look back and road ahead. Pathol Res Pract 239: 154144.
3. European Centre for Disease Prevention and Control (2025) SARS-CoV-2 variants of concern as of 25 April 2025.
4. Indian SARS-CoV-2 Genomics Consortium.
5. WHO TAG-VE Risk Evaluation for SARS-CoV-2 Variant Under Monitoring: NB.1.8.1.1.8.1.
6. Tracking SARS-CoV-2 variants.
7. 273 Cases In Kerala In May, 23 In Delhi: COVID-19 Cases Surge Across India, Experts say 'Rise Not a Worry'.
8. COVID Update: 2 JN.1 Descendants Found In India Amid Surge Scare; 1 Death Reported In Thane.
9. No need to panic over new Covid variant, precautions still key: Doctors.
10. Should you be worried about Covid variant JN.1? Check what doctors are saying.
11. Park GW, Reija B, Tamin A, Hicks H, Flanders MH, et al. (2025) Comparative analysis of environmental persistence of SARS-CoV-2 variants and seasonal coronaviruses. Appl Environ Microbiol 91: 0168824.
12. New Covid variant NB.1.8.1 detected at US airports amid rise in cases. Check for symptoms and preventive measures.
13. WHO TAG-VE Risk Evaluation for SARS-CoV-2 Variant Under Monitoring: NB.1.8.1.
14. Xue S, Han Y, Wu F, Wang Q (2024) Mutations in the SARS-CoV-2 spike receptor binding domain and their delicate balance between ACE2 affinity and antibody evasion. Protein Cell 15: 403-418.
15. Zabidi NZ, Liew HL, Farouk IA, Puniyamurti A, Yip AJW, et al. (2023) Evolution of SARS-CoV-2 Variants: Implications on Immune Escape, Vaccination, Therapeutic and Diagnostic Strategies. Viruses 15: 944.
16. Aden D, Zaheer S (2024) Investigating the FLiRT variants of COVID-19: Is it an emerging concern? Pathol Res Pract 262: 155542.
17. World Health Organization (2025) Tracking SARS-CoV-2 Variants. WHO, Geneva, Swizerland.
18. Pather S, Charpentier N, Ouweland FVD, Rizzi R, Finlayson A, et al. (2024) A Brighton Collaboration standardized template with key considerations for a benefit-risk assessment for the Comirnaty COVID-19 mRNA vaccine. Vaccine 42: 126165. 
19. New Covid variant NB.1.8.1 detected at US airports amid rise in cases. Check for symptoms and preventive measures.
20. New Covid NB.1.8.1 and LF.7 subvariants detected in India as cases tick up in pockets.
21. What to Know About the ‘FLiRT’ Variants of COVID-19.
22. Carabelli AM, Peacock TP, Thorne LG, Harvey WT, Hughes J (2023) SARS-CoV-2 variant biology: immune escape, transmission and fitness. Nat Rev Microbiol 21: 162-177.
23. Over 1000 Infected: Symptoms Linked To The New COVID Variants NB.1.8.1 and LF.7; Should India Worry?.
24. Symptoms of COVID-19.
25. Koyama AK, Siegel DA, Oyegun E, Hampton W, Maddox N, et al. (2021) Symptoms Reported With New Onset of Loss of Taste or Smell in Individuals With and Without SARS-CoV-2 Infection. JAMA Otolaryngol Head Neck Surg 147: 911-914.
26. Adly HM, Saleh SAK, Garout MA, Abdulkhaliq AA, Khafagy AA, et al. (2023) Post COVID-19 Symptoms Among Infected Vaccinated Individuals: A Cross-Sectional Study in Saudi Arabia. J Epidemiol Glob Health 13: 740-750.
27. COVID variants, NB.1.8.1, LF.7, detected in India; Check if its deadly, symptoms, preventive measures, other details.
28. Most Covid-19 infections ‘mild’: Health ministry urges vigilance as new variant JN.1 detected | All you need to know.
29. Lamba S, Ganesan S, Daroch N, Paul K, Joshi SG, et al. (2023) SARS-CoV-2 infection dynamics and genomic surveillance to detect variants in wastewater - a longitudinal study in Bengaluru, India. Lancet Reg Health Southeast Asia. 11: 100151.
30. Jian F, Yisimayi A, Song W, Wang J, Xu Y, et al. (2024) Humoral immunogenicity comparison of XBB and JN.1 in human infections. bioRxiv 2024.
31. India detects cases of new NB.1.8.1 and LF.7 COVID strains; experts say no need to panic.
32. Long COVID Basics.
33. Centers for Disease Control and Prevention (CDC) Seasonal Influenza and COVID-19: Considerations for Health Systems.
34. World Health Organization (WHO). Risk Communication and Community Engagement for Influenza and COVID-19.
35. What’s behind the recent Covid-19 spike in India?
36. Integrated Disease Surveillance Programme.
37. Delhi government issues advisory to hospitals amid rising COVID-19 cases.
38. Testing for COVID-19.
39. Shahid S, Parveen S, Vyas N, Abuhasaballah HHA, Annadurai S, et al. (2024) Tracking of SARS-CoV-2 Variants of Concern by RT-PCR Assay in the Post-Pandemic Era. New Emirates Medical Journal 5: 0250-6882.
40. Lerner AM, Folkers GK, Fauci AS (2020) Preventing the Spread of SARS-CoV-2 With Masks and Other “Low-tech” Interventions. JAMA324: 1935-1936.
41. Aden D, Zaheer S, Raj S (2022) Challenges faced in the cancer diagnosis and management-COVID-19 pandemic and beyond-Lessons for future. Heliyon 8: 12091.
42. Hand Sanitizer Guidelines and Recommendations.
43. COVID-19 symptoms and what to do.
44. Isolation Precautions Guideline.
45. Aden D, Zaheer S, Kumar R, Ranga S (2023) Monkeypox (Mpox) outbreak during COVID-19 pandemic-Past and the future. J Med Virol 95: 28701.
46. Advice for the public: Coronavirus disease (COVID-19).
47. Menegale F, Manica M, Zardini A, Guzzetta G, Marziano V, et al. (2023) Evaluation of Waning of SARS-CoV-2 Vaccine-Induced Immunity: A Systematic Review and Meta-analysis. JAMA Netw Open 6: 2310650.
48. Shete AM, Patil DY, Sahay RR, Sapkal GN, Deshpande GR, et al. (2022) Waning natural and vaccine-induced immunity leading to reinfection with SARS-CoV-2 Omicron variant. Hum Vaccin Immunother 18: 2127289.
49. Khoury DS, Schlub TE, Cromer D, Steain M, Fong Y, et al. (2023) Correlates of Protection, Thresholds of Protection, and Immunobridging among Persons with SARS-CoV-2 Infection. Emerg Infect Dis 29: 381-388.
50. Murhekar MV, Bhatnagar T, Thangaraj JWV, Saravanakumar V, Kumar MS, et al. (2021) ICMR Sero surveillance Group. SARS-CoV-2 seroprevalence among the general population and healthcare workers in India, December 2020-January 2021. Int J Infect Dis 108: 145-155.
51. Khan K, Lustig G, Römer C, Reedoy K, Jule Z, et al. (2023) Evolution and neutralization escape of the SARS-CoV-2 BA.2.86 subvariant. Nat Commun 14: 8078.
52. Bergeri I, Whelan MG, Ware H, Subissi L, Nardone A, et al. (2022) Global SARS-CoV-2 seroprevalence from January 2020 to April 2022: A systematic review and meta-analysis of standardized population-based studies. PLoS Med 19: 1004107.
53. Tarke A, Coelho CH, Zhang Z, Dan JM, Yu ED, et al. (2022) SARS-CoV-2 vaccination induces immunological T cell memory able to cross-recognize variants from Alpha to Omicron. Cell 185: 847-859.
54. Keeton R, Tincho MB, Ngomti A, Baguma R, Benede N, et al. (2022) T cell responses to SARS-CoV-2 spike cross-recognize Omicron. Nature 603: 488-492.
55. Lau JJ, Cheng SMS, Leung K, Lee CK, Hachim A, et al. (2023) Real-world COVID-19 vaccine effectiveness against the Omicron BA.2 variant in a SARS-CoV-2 infection-naive population. Nat Med 29: 348-357.
56. Mukhopadhyay L, Gupta N, Yadav PD, Aggarwal N (2022) Neutralization assays for SARS-CoV-2: Implications for assessment of protective efficacy of COVID-19 vaccines. Indian J Med Res 155: 105-122.
57. Sharma N, Basu S, Lalwani H, Rao S, Malik M, et al. (2023) COVID-19 Booster Dose Coverage and Hesitancy among Older Adults in an Urban Slum and Resettlement Colony in Delhi, India. Vaccines 11: 1177.
58. Rizvi AA, Singh A (2022) Vaccination coverage among older adults: a population-based study in India. Bull World Health Organ 100: 375-384.
59. Das S, Kar SS, Samanta S, Banerjee J, Giri B, et al. (2022) Immunogenic and reactogenic efficacy of Covaxin and Covishield: A comparative review. Immunol Res 70: 289-315.
60. Mahumud RA, Ali MA, Kundu S, Rahman MA, Kamara JK, et al. (2022) Effectiveness of COVID-19 Vaccines against Delta Variant (B.1.617.2): A Meta-Analysis. Vaccines 10: 277.
61. Zhou Z, Zhu Y, Chu M (2022) Role of COVID-19 Vaccines in SARS-CoV-2 Variants. Front Immunol 13: 898192.
62. Pather S, Charpentier N, Ouweland FVD, Rizzi R, Finlayson A, et al. (2024) A Brighton Collaboration standardized template with key considerations for a benefit-risk assessment for the Comirnaty COVID-19 mRNA. Vaccine 42: 126165.
63. Ella R, Reddy S, Jogdand H, Sarangi V, Ganneru B, et al. (2021) Safety and immunogenicity of an inactivated SARS-CoV-2 vaccine, BBV152: Interim results from a double-blind, randomised, multicentre, phase 2 trial, and 3-month follow-up of a double-blind, randomised phase 1 trial. Lancet Infect Dis 21: 950-961.
64. Tobias J, Steinberger P, Wilkinson J, Klais G, Kundi M, et al. (2024) SARS-CoV-2 Vaccines: The Advantage of Mucosal Vaccine Delivery and Local Immunity. Vaccines 12: 795.
65. Ministry of Health and Family Welfare, Government of India. Operational Guidelines for COVID-19 Preparedness and Response in India.
66. Interim Clinical Considerations for Use of COVID-19 Vaccinesin the United States.
67. Yang J, Rai KK, Alfred T, Massey L, Massey O, et al. (2025) The impact of COVID vaccination on incidence of long COVID and healthcare resource utilisation in a primary care cohort in England, 2021-2022. BMC Infect Dis 25: 214.
68. Català M, Mercadé-Besora N, Kolde R, Trinh NTH, Roel E, et al. (2024) The effectiveness of COVID-19 vaccines to prevent long COVID symptoms: staggered cohort study of data from the UK, Spain, and Estonia. Lancet Respir Med 12: 225-236.
69. Surveillance and Data Analytics.
70. Soukhovolsky V, Kovalev A, Pitt A, Shulman K, Tarasova O, et al. (2021) The Cyclicity of coronavirus cases: "Waves" and the "weekend effect". Chaos Solitons Fractals 144: 110718.
71. Filip R, Puscaselu RG, Anchidin-Norocel L, Dimian M, Savage WK (2022) Global Challenges to Public Health Care Systems during the COVID-19 Pandemic: A Review of Pandemic Measures and Problems. J Pers Med 12: 1295.