Thread by @DrEricDing

📬MAIL DELIVERY OUTBREAK—China’s CDC reports an outbreak of #Omicron “likely caused” by an international postal letter. Genetically distinct from other cases, but linked to SE Asia & N America. If true—this is the first outbreak cluster spread such way.🧵
weekly.chinacdc.cn/en/article/doi…

2) Study concludes: “we reported the first local cluster caused by Omicron variant in Beijing and showed this cluster was likely caused by a contaminated internationally mailed document, which has not been reported before.”

3) “Our data emphasized the surveillance and disinfection of imported express cargo in COVID-19”

Aside—I think seasonality here matters. January is dead of winter and Beijing is very cold then.

4) “The field investigation was performed to identify the source of infection. Case A lived and worked in Haidian District, Beijing, without travel history out of Beijing or close contact with local or imported high-risk populations.

5) “Further investigation indicated that the case sent and received international mail occasionally. Notably, an internationally mailed document was received by the case on January 11 (2 days before onset of symptoms), which was delivered from abroad on January 7.

6) “The disinfection was carried out from the outer surface of the packaged document when it arrived in Beijing. A total of 1,054 environmental samples were collected, including 22 swabs for the package received by the case.

7) “The qRT-PCR showed that 12 of 22 samples were positive in the SARS-CoV-2 ORF1ab/N gene test, including 2 samples collected from the outer surface of the package, 2 from the inner package, and the other 8 from contained papers.“ and all 12 Omicron.

8) “Phylogenetic analysis indicated the virus located near the cluster of some strains collected in North American and Southeast Asia in mid-December, which had significant differences with local clusters in China in the same period (Figure 1).

9) “This is the first local cluster caused by Omicron variant in Beijing.” 👀 (which make them even more sure it was mail not community).

“A remarkable finding of this study was the possible source of the infection for this cluster.”

10) “We proposed the infection was induced by the internationally mailed document, mainly based on the following evidence. Field investigations showed no potential exposure of the case except the internationally mailed document, with an onset interval of 2 days.

11) “All identified cases showed epidemiological links with Case A. Environmental surveillance identified SARS-CoV-2 RNA positive samples from the package’s contents, and part of these positive contents were untouched by the case.

12) “More importantly, NGS showed that the genome of the case matched the samples collected from the mailed documents, which differed from other local strains in China.” 👀

13) I think this is still very rare and maybe a unique winter / frozen climate situation. The WHO has discussed this frozen temperature unique situation before—and @WHO acknowledges frozen food cold chain can be a possible (albeit rare) source for transmission.

https://twitter.com/drericding/status/1359111942246383620

14) to be honest, most countries don’t investigate or trace to this degree. China has been diligently tracing for a long time.

https://twitter.com/drericding/status/1309351833085841409

15) And the earlier frozen fish case was later confirmed in a formal investigation

https://twitter.com/DrEricDing/status/1317925577488322561

16) Also, remember that old unsolved mystery of how New Zealand found that one case that triggered a cluster? In that unsolved outbreak—“Authorities have traced the virus to a worker in a cold-storage 🥶 warehouse, but they can’t figure out how he got it” wsj.com/articles/coron…

17) That said, do not lose sight that overall #COVIDisAirborne — very airborne. This is the most detailed thread 🧵 I’ve written on the subject 👇 —protect yourself and your family.

https://twitter.com/drericding/status/1471054758085632002

18) Wow—this other new study shows Omicron survives on most surfaces much longer than the old strain.

Dr Marr is an airborne scientist so she even acknowledges this new concern of Omicron.

https://twitter.com/linseymarr/status/1502378512753307649

19) Another recent study also shows #Omicron surviving longer than the old Wuhan strain and Delta. Omicron does seem environmentally sturdier, which can help it transmit better.

https://twitter.com/__philipn__/status/1502389420573429760