What is ‘stealth’ Omicron or Omicron BA.2? All you need to know

As the third wave of the pandemic subsides across the globe, the surge of fresh cases has sparked speculations of a fourth wave of the Covid-19 pandemic. The rise in new cases is largely being attributed to the ‘stealth Omicron’ variant in the UK, Israel, South Korea, China, Philippines, Nepal, Qatar, Denmark and the US where the variant represents 23 per cent of the cases. Tamil Nadu has also reported cases of 'stealth Omicron' or Omicron BA.2, a sub-variant of the highly transmissible strain.

The Tamil Nadu public health department stated that it has found that BA.2 sub-variant of Omicron was in 18.4 per cent of the samples sequenced in the state from January to March 2022. The genomic analysis on the samples also found that the sub-variant BA.1.1 was identified in 43 per cent of the samples while the BA.1 sub-variant was found in 37.3 per cent of the samples. The health department has said that Omicron was the dominant variant in circulation in the state.

Research by Denmark’s Statens Serum Institut (SSI) found that ‘stealth Omicron’ could be 1.5 times more infectious than its predecessor. In addition, the ‘stealth Omicron’ variant is tougher to be identified in PCR tests as the new variant misses key mutations in spike protein that are necessary for rapid PCR tests to identify the infection.

Stealth Omicron combines two sub-variants of the Omicron version of the Covid virus named BA.1 and BA.2. Several studies have proven that reinfection with BA.2 (stealth Omicron) following infection with BA.1 (Omicron) provides stronger protection against reinfection with BA.2.

According to WHO, the 'stealth Omicron' variant primarily affects the upper respiratory tract. Unlike Delta, the BA.2 variant does not affect the lungs, and patients don't experience shortness of breath, loss of smell and taste.

Stealth Omicron impacts the upper respiratory system of a human body, which leads to more flu-like symptoms and not loss of smell, taste and breathing issues, WHO said. Symptoms appear in two to three days after catching the virus include fever, extreme fatigue, coughing, sore throat, sore head, muscular fatigue and elevated heart rate.