Out of 279 swab samples tested during the 12th genome sequencing series in the metropolis, 278 were found infected with Omicron sub-variants of coronavirus and one with the Delta strain, the Brihanmumbai Municipal Corporation (BMC) said on Monday. The civic body said 279 COVID-19 samples were examined in the 12th series batch at the Genome Sequencing Lab in BMC-run Kasturba Hospital. Out of the total, 202 samples were collected from Mumbai, while the remaining were from outside the city. It said among the 202 samples in Mumbai, 201 (99.5 per cent) were infected with Omicron sub-variants of coronavirus, while one was detected with the Delta strain.