Infections caused by Omicron BA.5 sub-lineage increasing in Karnataka

While BA.2 continues to be the dominant strain, BA.5, found in 112 samples till June end, has been detected in 279 samples in July

August 10, 2022 08:40 pm | Updated 09:45 pm IST - Bengaluru

The presence of BA.5 sub-lineage was initially detected in the last week of May through sewage surveillance in Bengaluru. 

The presence of BA.5 sub-lineage was initially detected in the last week of May through sewage surveillance in Bengaluru.  | Photo Credit: File photo

The number of infections caused by Omicron’s BA.5 sub-lineage are on the rise in Karnataka. According to data from the State Health and Family Welfare Department, BA.5 has contributed 21.89% of the total 1,300 samples sequenced in July in the State.

This sub-lineage that was found in 112 samples till June end has been detected in 279 samples in July, data showed. However, Omicron’s BA.2 continues to be the dominant strain in Karnataka so far contributing 48.50% of the total samples sequenced in July.

The presence of BA.5 sub-lineage was initially detected in the last week of May through sewage surveillance in Bengaluru. The Indian SARS-CoV -2 Genomics Consortium (INSACOG) confirmed it only a month later on June 21. So far, 15,293 samples have been sequenced in Karnataka.

According to INSACOG’s July report, while 279 samples have been found to be infected with BA.5, 618 samples were found to be infected with BA.2 sub-lineage.

Different sub-lineages

Overall, 98% of the total 1,300 samples sequenced in July have been found to be infected with different sub-lineages of Omicron. This includes BA1.1.529 (27.55%), BA.2 (48.50%), BA.5 (21.89%), BA.4 (1.64%), and BA.3 (0.39%).

While Delta was the dominant strain during the first wave with 90.7% of the 4,441 samples, sequenced from March 2021 to December 2021, found to be infected with it, 87.8% of the 9,552 samples, sequenced from January till June 2022, were found to be infected with Omicron.

Rise in hospitalisation

With the rise in BA.5 infections, the State has also recorded a rise in hospitalisation and deaths. From 107 hospital admissions on June 30, the number has gone up to 221 now. Of these, only 56 are from Bengaluru Urban.

While 29 deaths were recorded in June, the first 10 days of August have already seen 24 deaths. Six and 10 deaths were recorded in May and June, respectively. However, experts said that it is too early to link this to the rise in BA.5.

State Health Commissioner Randeep D. said most of the deaths are among senior citizens with comorbidities. “Surveillance will be intensified now to curb the spread in clusters. Besides targeted testing of ILI/SARI cases, we have directed health staff to mandatorily test all primary contacts of positive persons, irrespective of symptoms,” he said.

Evades previous immunity

V. Ravi, who heads the State’s genomic surveillance committee, said BA.5 has better fitness for human cell receptors. “This sub-lineage is able to evade previous immunity - both due to a prior infection and vaccine-induced. Even those who have taken booster doses can get infected. But the infection can be mild, similar to a flu among the vaccinated,” Dr. Ravi said.

“As the new sub-lineages are highly transmissible, masking up is the best weapon. People should wear masks at least in crowded areas,” he said.

Surge in ILI/SARI

Rajath Athreya, member of the State’s COVID-19 Technical Advisory Committee (TAC), said there is a huge surge in ILI/SARI cases, most of which are non-COVID. “However, we may have to wait and watch for another week or 10 days to understand if the circulating sub-lineages are leading to a rise in hospitalisation that require oxygen,” he added.

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