After the third wave driven by the Omicron sub-lineage BA.2 peaked in end-January this year with over 0.33 million cases a day, there has been a small bump in the number of daily cases reported in the first fortnight of June and a slightly bigger increase in the last one week to touch over 13,200 cases on June 17. But the rate of increase has been small and restricted to a few States and some major cities. The rate of growth of active cases has also been low. While the sub-lineage BA.2 is still the dominant strain in India, BA.4 and BA.5 seem to be causing the new cases. The small increase in testing in the past week could be a reason for the more cases reported. The seven-day average test positivity rate doubled from less than 1% in early June to over 2% by mid-June and has been increasing incrementally since then to 2.7% on June 20. Increasing the number of daily tests will result in more cases being detected. But with a large percentage of the adult population fully vaccinated and a sizable percentage also infected, the focus should be more on hospitalisations and deaths and not daily infections. There has been a slight increase in hospitalisation in a few States, but there is no cause for alarm. However, there has not been any increase in daily deaths. The small bump in daily cases seen in a few States for the last three weeks therefore does not appear to mark the beginning of a new wave.
That said, the BA.4 and BA.5 sub-lineages are fast spreading to more countries in Europe with a concomitant increase in cases. The BA.5 sub-lineage has become dominant in Portugal leading to a surge in daily infections, hospitalisations and even deaths despite very high primary and booster dose vaccination coverage; the reasons for increased deaths are not known. With both BA.4 and BA.5 endowed with greater transmissibility and higher immune escape from vaccination and earlier infection, including of the BA.1 and BA.2 Omicron sub-lineages, the European Centre for Disease Prevention and Control designated them as variants of concern in mid-May; WHO too has given the same designation. On June 13, the ECDC cautioned that these sub-lineages will become dominant throughout Europe leading to increased daily cases. However, it notes that based on limited data, the two sub-lineages do not appear to be associated with increased disease severity compared with the BA.1 and BA.2 Omicron sub-variants. Given the greater transmissibility of BA.4 and BA.5 and immune escape, the sub-lineages may become dominant in India too, especially as COVID-appropriate behaviour is now poor. While the two sub-lineages may not lead to increased deaths, the risk of long-term complications even among the young and healthy when infected cannot be overlooked. Masks must be made mandatory, especially in public and closed spaces with poor ventilation.
