In recent weeks, there have been frequent reports about the rise of the more transmissible Omicron subvariant BA.2 around the world. BA.2 now makes up nearly all the new cases in Denmark, the U.K.,…
, the U.K., Switzerland, Sweden, India, Belgium, Norway, South Africa, The Philippines, Hong Kong and many more regions.
, which pulls worldwide data on the genomically-sequenced samples submitted to the GISAID data-sharing hub. In fact, since late January, identified cases of BA.2 have doubled every two weeks in the U.S.The growth of Omicron variant BA.2 shown, in lavender, vs. the original Omicron, in purpleThe first identified cases of BA.2 in the United States appeared at roughly the same time as they did in the U.K. and Denmark: late November & early December 2021.
The reasons for the differences in rates of spread among countries are unclear. “The difference in growth potential between countries may be linked to differences in vaccination coverage and contact patterns arising because of restrictions, population densities, etc.,” a WHO report suggested. As for population density, the U.K. is overall far more concentrated than Denmark, which itself is denser than the United States — which, of course, does have its own highly dense urban centers.