Karnataka logs 219 'stealth Omicron' cases since Jan 1

Of the 1,115 Omicron cases reported in Karnataka till Thursday, 219 were the sub-variant Ba.2 (known as ‘stealth Omicron’), prompting virologists to urge the government to expedite studies to understand its virulence and potential impact on public health at a time when the third wave was waning.

The breakup of the cases was made public by the Health Department late Thursday night. Virologists who spoke to DH said there was a need to study the clinical manifestations of the Ba.2 patients, including the number of deaths, to establish its transmissibility and virulence.

A scientist at CSIR Institute of Genomics and Integrative Biology, New Delhi, who did not want to be named said, “Data from the UK and Denmark show that Ba.2 is more transmissible, therefore likely to reach more people faster, and in secondary effect causes more net mortality in a short period.”

Concerns arose after a Danish study said Ba.2 was more contagious than Ba.1. It said Ba.2 also “possesses immune-evasive properties that reduce the protective effect of vaccination against infection”.

Also read: Omicron BA.2 sub-variant dominant in South Africa, says CDC

However, virologist and microbiologist Dr Gagandeep Kang, also a professor at Christian Medical College (CMC), Vellore, said all SARS-CoV-2 variants can cause severe disease and death in old and comorbid patients. “The number of Ba.2 cases alone do not indicate greater severity, which can be determined only after studying more data on testing, timing and individuals who died.” Karnataka is set to complete special genomic sequencing of 10,000 samples on February 28. One of the priority groups for sequencing are Covid dead. It is yet to analyse how many of the Ba.2 patients needed hospitalisation, oxygen support, ICU care, or died.

Health Commissioner D Randeep said, “We don’t have this reverse analysis as yet. We have asked them (health department) to identify from death audit reports and genomic sequencing reports.”

India’s foremost epidemiologist Dr Jayaprakash Muliyel told DH, “The stealth Omicron is faster-moving and more infectious than Ba.1, and consequently it is overtaking Ba.1. Ba.2 does not exhibit the S-gene dropout and that is why it is different. Fortunately, it doesn’t behave like Delta clinically. It is highly immunogenic but has low pathogenicity.”

Karnataka has reported 89 Ba.1 cases so far, 85 of which were reported from January 1.

Dr T Jacob John, retired professor and head of departments of clinical virology and microbiology at CMC Vellore, said, “What Karnataka should announce is the clinical presentation of the 219 individuals with Ba.2. If the symptoms are different from Ba.1, then it is a cause for concern. Also, if we use an S-gene dropout test to detect Ba.2 we won’t find it as it doesn’t exhibit the S-gene dropout.”

The World Health Organisation’s (WHO) incident manager Abdi Mahamud said on February 9 that 5 lakh deaths have been recorded globally since Omicron was declared a variant of concern in late November.

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