Eligible vacationers may just volunteer to offer a self-collected nasal swab on the airport. Swabs from 5 to twenty-five vacationers — from the similar flight or nation — have been added to a unmarried tube after which examined for the virus the use of P.C.R. checking out. Sure samples have been then sequenced to resolve which model of the virus used to be provide.
Between Sept. 29 and Jan. 23, 10 p.c of 161,000 eligible vacationers enrolled within the learn about, and 1,454 pattern swimming pools have been examined for the virus. Regardless of the preflight checking out requirement, greater than 15 p.c of the swimming pools have been certain.
This slightly top positivity charge might point out that vacationers have been early for the duration of their infections — and thus had viral so much too low for some exams to stumble on — once they took their predeparture exams, or that they shrunk the virus within the time between being examined and touchdown in the USA, the researchers say. Other folks may additionally have submitted fraudulent take a look at effects.
Ahead of Nov. 28, just about the entire certain pattern swimming pools contained the Delta variant, the researchers discovered. (The one exception used to be a good pattern whose actual genetic lineage may just now not be made up our minds.)
After that, alternatively, Omicron temporarily got here to dominate; from Nov. 28 to Jan. 23, two-thirds of the certain samples have been Omicron. Lots of the Omicron samples have been the BA.1 subvariant, which used to be to start with essentially the most prevalent model international. BA.1 stays the commonest lineage in the USA, regardless that BA.2 has been gaining floor and now accounts for 35 p.c of infections, consistent with C.D.C. estimates.
However the researchers discovered the BA.3 subvariant in a pool of samples gathered from vacationers getting back from South Africa on Dec. 3. They reported the discovering in GISAID, a world repository of viral genomes, on Dec. 22. It used to be the primary reported case of BA.3 in the USA; it could be greater than a month prior to the following used to be reported.
The airport program additionally detected the primary recognized U.S. case of BA.2, in samples gathered from South African vacationers on Dec. 14. The researchers reported the discovering per week prior to the following U.S. case of BA.2 used to be reported.
“It is a new device within the C.D.C. device package that works, and we’ve proven it’s efficient and it may be layered with all of our different mitigation measures,” Dr. Friedman mentioned.