Is omicron BA.2 as transmissible as omicron BA.1?
Over the past several weeks, omicron BA.2 has begun to surprise scientists. And it's starting to look like it can, in some countries, outcompete its sibling omicron BA.1 — and, really, any other variants.
Back in December, omicron BA.1 caused a massive surge in cases in Denmark, similar to the surge in the United States. But then, just as cases began to decline, BA.2 started spreading very rapidly in Denmark. After only a few weeks, BA.2 took over the outbreak there and has lengthened Denmark's surge. Denmark's cases are climbing steeply, with more than 40,000 recorded each day. Since the second week in January, BA.2 has caused more than 50% of those cases, according to the Statens Serum Institut in Copenhagen.
Omicron BA.2 is also growing exponentially in England and Germany, where it's causing at least 5% of cases in both places. Scientists are concerned it could lengthen surges in those locations as well as possibly in the United States.
Together, this data indicates that BA.2 is not BA.1's weaker sibling, but rather that BA.2 is quite strong and possibly more contagious.
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"Scientists there have found that there was no increased risk in going to the hospital if you have BA.2 compared to if you have BA.1," Chin-Hong says. "That could change, but that's what we know so far."