An airport-based coronavirus surveillance program in the US for vacationers arriving from overseas detected the primary identified U.S. case of the extremely contagious Omicron subvariant BA.2 in December, according to a new study.
The outcomes, which haven’t but been printed in a peer-reviewed journal, recommend that pooled testing of worldwide vacationers could also be an efficient and environment friendly option to maintain tabs on new variants and pathogens.
“Vacationers are actually an vital inhabitants when monitoring new and rising infectious illnesses as a result of they’re cellular, they’ve the potential for publicity to illness throughout journey and so they can unfold illness from one place to a different,” mentioned Dr. Cindy R. Friedman, chief of the Vacationers’ Well being Department at Facilities for Illness Management and Prevention, and the examine’s lead investigator.
This system truly detected the primary identified U.S. circumstances of two Omicron subvariants, BA.2 and BA.3, which are similar to, but genetically distinct from, BA.1 and B.1.1, the variations of Omicron that drove a winter surge in U.S. circumstances.
The voluntary program, which screened greater than 16,000 vacationers this fall and winter, was carried out by the C.D.C. and two industrial companions: the XpresSpa Group, which affords testing in airports, and Ginkgo Bioworks, a biotech firm with a testing initiative and a community of laboratories throughout the nation. This system mixed nasal samples from a number of folks arriving from the identical nation or on the identical flight — an strategy, often called pooled testing, that permits scientists to seek for the virus in a number of folks directly.
This system was not the primary to catch each model of Omicron; BA.1, the subvariant that was initially most prevalent worldwide, didn’t present up in one of many airport samples till Dec. 1, the identical day that officers introduced that one other group of researchers had discovered the first U.S. Omicron case.
The researchers hope to broaden the traveler surveillance program and are additionally making ready to launch a pilot examine that may seek for indicators of the virus within the wastewater from airplane bogs, Dr. Friedman mentioned.
This system started in late September, specializing in vacationers on chosen flights from India to a few main U.S. airports: John F. Kennedy Worldwide Airport in New York, Newark Liberty Worldwide Airport in New Jersey and San Francisco Worldwide Airport in California. In late November, after Omicron emerged, this system was expanded to Hartsfield-Jackson Atlanta Worldwide Airport and to folks arriving from South Africa, Nigeria, Britain, France, Germany and Brazil.
(Omicron prompted the Biden administration to tighten journey guidelines. It briefly banned travelers from eight African countries — the restrictions didn’t apply to U.S. residents or everlasting residents — and required worldwide passengers to current proof that they’d examined unfavorable for the virus within a day before departure. Beforehand, vacationers might take a look at inside three days of departure. As of Nov. 8, only vaccinated foreign travelers were allowed into the country.)
Eligible vacationers might volunteer to offer a self-collected nasal swab on the airport. Swabs from 5 to 25 vacationers — from the identical flight or nation — have been added to a single tube after which examined for the virus utilizing P.C.R. testing. Constructive samples have been then sequenced to find out which model of the virus was current.
Between Sept. 29 and Jan. 23, 10 % of 161,000 eligible vacationers enrolled within the examine, and 1,454 pattern swimming pools have been examined for the virus. Regardless of the preflight testing requirement, greater than 15 % of the swimming pools have been constructive.
This comparatively excessive positivity price could point out that vacationers have been early in the midst of their infections — and thus had viral masses too low for some checks to detect — once they took their predeparture checks, or that they contracted the virus within the time between being examined and touchdown in the US, the researchers say. Individuals can also have submitted fraudulent take a look at outcomes.
Earlier than Nov. 28, almost the entire constructive pattern swimming pools contained the Delta variant, the researchers discovered. (The one exception was a constructive pattern whose precise genetic lineage couldn’t be decided.)
After that, nonetheless, Omicron rapidly got here to dominate; from Nov. 28 to Jan. 23, two-thirds of the constructive samples have been Omicron. A lot of the Omicron samples have been the BA.1 subvariant, which was initially probably the most prevalent model worldwide. BA.1 stays the commonest lineage in the US, although BA.2 has been gaining floor and now accounts for 35 % of infections, according to C.D.C. estimates.
However the researchers discovered the BA.3 subvariant in a pool of samples collected from vacationers arriving from South Africa on Dec. 3. They reported the discovering in GISAID, a global repository of viral genomes, on Dec. 22. It was the primary reported case of BA.3 in the US; it could be greater than a month earlier than the following was reported.
The airport program additionally detected the primary identified U.S. case of BA.2, in samples collected from South African vacationers on Dec. 14. The researchers reported the discovering per week earlier than the following U.S. case of BA.2 was reported.
“It is a new device within the C.D.C. device equipment that works, and we’ve proven it’s efficient and it may be layered with all of our different mitigation measures,” Dr. Friedman mentioned.