World Health Organization tracking delta, omicron combination variant Measles one of most contagious diseases known to humans LONDON: The new omicron subvariant of COVID-19 was almost as infectious as measles, one of the most contagious diseases in human history, a top virus expert has warned. The variant — dubbed deltacron because it combines elements of the omicron and delta variants — has been detected in parts of France and is understood to have been circulating since January. Prof. Adrian Esterman, a former World Health Organization epidemiologist, told ABC news that although the symptoms of deltacron were not any more severe than omicron, it was more transmissible. He said: “That means we’re going to see case numbers skyrocketing.” In a tweet, he added: “Omicron BA.2 is about 1.4 times more infectious than BA.1. The basic reproduction number (R0) for BA.1 is about 8.2, making R0 for BA.2 about 12. This makes it pretty close to measles, the most contagious disease we know about.” Just a few cases of the latest variant have so far been detected and it was not yet clear how vaccines would perform against it. In a tweet, Soumya Swaminathan, the WHO’s chief scientist, said: “We have known that recombinant events can occur, in humans or animals, with multiple circulating variants of #SARSCoV2. “Need to wait for experiments to determine the properties of this virus. Importance of sequencing, analytics, and rapid data sharing as we deal with this pandemic.” Also in a tweet, COVID-19 technical lead for the WHO, Maria van Kerkhove, said her team was “tracking and discussing” the new variant.