The ECDC (European Center for Disease Prevention and Control) has expressed concern about these two sub-variants. Will a new epidemic wave be caused by sub-variants of Omicron? Europe, through its Center for Disease Prevention and Control (ECDC) has categorized the subvariants BA.4 and BA.5 as ‘Variants of interest’. These Omicron mutations, first detected in South Africa in January and February 2022, present evidence that they could have an impact on the epidemiological situation in Europe, indicates the ECDC website. To read also: Covid – Omicron: first case of the BA.5 sub-variant detected in France However, the agency does not have, for the moment, any data concerning its transmissibility, its impact on immunity and its severity . Its transmission is sporadic and occurs especially during travel. The L452X mutation of the BA.2 variant placed under surveillance In its weekly report, the ECDC places in the category “Variants under surveillance” the L452X mutation of the BA.2 sub-variant. This could have properties similar to those placed in the ‘Variants of Concern’ box (the strongest monitoring category) but the ECDC is not collecting enough evidence. It joins in this category of “variants under surveillance” the sub-variants XD and BA.3. Also read: Covid – Omicron: growth advantage, contagiousness, severity, why is the WHO carefully monitoring the new BA.4 and BA.5 variants?