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New Subvariant Arcturus: India and the World

Tracking the rise of SARSCoV2 Lineage XBB/1/16 over a 12 week period (Nickname: Arcturus). Shows exponential rise in the virus spread.
Tracking XBB.1.16 Lineage Over Time. [1]

XBB.1.16, dubbed “Arcturus,” is surging in India, outcompeting other variants, including Kraken (XBB.1.5), and is spreading globally. 

According to a recent report [2], it is 1.2 times more infectious than the highly infectious Kraken variant that quickly took dominance in early 2023. Researchers state that Arcturus’ growth advantage over other variants is due to: 1) increased binding to cell receptors; and 2) increased viral growth efficiency. Researchers expect Arcturus to spread world-wide due to its advantage over other variants in circulation. 

Already, it has been reported in several US states – with the highest cases in California, Washington, New Jersey, New York, Virginia and Texas – and the numbers are increasing over time [3]. 

India recorded 10,158 new COVID cases in 24 hours [4] on Thursday, April 13th – a 30% surge in one day, according to the federal health ministry data. For comparison, on the 1st of January, India was recording less than 300 new cases per day with a 0.1% positivity, compared to over 4% positivity now. The Arcturus surge is the highest in nearly 8 months, and has caused India’s health ministry to take actions, including holding drills for hospitals, stocking supplies, and restarting vaccine production. Some states have again made mask-wearing in public mandatory, as part of India’s stepped-up efforts to defend against new variants [5]. Mumbai, the largest city and financial capital of India, mandated the use of face masks for employees, patients and visitors in all civic-run hospitals [6], including providing a security staff at the front door of the hospitals to ensure adherence. Masks have not been compulsory in the area since March 2022 [7]. 

Similar to past variants, common symptoms of Arcturus include fever, shortness of breath, and cough. However, doctors in India are reporting rising cases among children with early symptoms of conjunctivitis, sticky eyes and diarrhea [8]. Hospitalization data typically lags behind case data, and severity of acute symptoms varies drastically among individuals, thus proactive steps to take caution should be reinforced.

Like Kraken [9], Arcturus exhibits profound immune evasion, with only one out of six clinically-available monoclonal antibodies (sotrovimab) exhibiting any antiviral activity, and even that effect was noted to be weak [10]. XBB variants are robustly resistant to a variety of anti-SARS-CoV-2 antibodies, and have high potential for breakthrough infections.  


[1] Tracking XBB.1.16 Lineage Over Time. Public Tableau. Accessed on April 12th 2023.  

[2] Virological characteristics of the SARS-CoV-2 Omicron XBB.1.16 variant. Published online April 6, 2023. doi:

[3] COVID Data Tracker. CDC. Accessed April 13, 2023.   

‌[4] Coronavirus in India live updates: India reports 10,158 new covid cases in 24 hours, highest in 230 days. The Times of India. Accessed April 13, 2023.   

[5] States urge citizens to wear masks as India updates its COVID-19 guidelines amid rising cases. Lifestyle Asia India. Published April 11, 2023.   

[6] BMC makes masks mandatory in Mumbai’s civic hospitals amid rising COVID-19 cases. Lifestyle Asia India. Published April 11, 2023.   

[7] WHO monitoring new Covid-19 subvariant “Arcturus”, which is driving surge of cases in India. The Star. Accessed April 13, 2023.   

[8] “Arcturus,” a highly transmissible COVID variant has a new symptom. Here’s what you need to know. India Today. Accessed April 13, 2023.   

[9] Omicron XBB.1.5 ‘Kraken’ Subvariant Is on the Rise: What To Know, Yale Medicine. Accessed April 17, 2023.

[10] The virological characteristics of XBB.1.16. Published April 12, 2023.