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New cases of #coronavirus in #Beijing are linked to a seafood market. Traces of the virus were found on a #salmon chopping board. It's very unlikely that this is a possible infection vector. Still, let's think through the possibilities.
The largest importers of salmon to China are Chile with 39% and Norway with 36% (Q1 2020). China has domestic salmon (TIL), but it's not competitive. seafoodsource.com/news/supply-tr…
Chile's salmon comes from large aquafarms, 60% of which are controlled by Norwegian capital.
However, Chilean salmon is much cheaper, which is mainly due to the lower labor costs. Workers work 12 hour shifts, 48 hours per week, at temperatures close to 0 °C. Image
Chile has notoriously bad working conditions. In 2019, workers were protesting for health care, among other things. Sick workers at processing plants are more likely to keep working despite feeling unwell. salmonbusiness.com/salmon-workers…
The workers should wear full protective gear, with protective suits, gloves and face masks. But even in the ideal case as here (journalists on visit!), we see a worker on the right hanging his nose over the face mask 😵 ImageImage
Secret videos show that workers don't always wear the protective gear correctly. Controls by the government administration lead to 70% of the cases to complaints over violated health and safety regulations - although controls are pre-scheduled.
Other regions farming salmon ir catching wikd salmon as Scotland or Alaska seem to have even less strict regulations regarding hygiene. Here some photos of workers without face masks. ImageImageImage
An infected worker could possibly spread fomites onto the surface of the fish, which then is kept at around 0°C to 1°C during transport by plane. The coronavirus can survive for several days on the surfaces, and longer for cold temperatures.
Because of the working conditions, disease are spreading easily among coworkers in a shift. Many sick workers mean more exposure on surfaces and knifes, smearing fomites all over the fish. Cutting fish produces messy, oily, wet liquids, as anyone who has cut fresh fish knows. Image
When the cutting board is clean at the start of the shift, all is good. But later on, it's like bathing all the fish in a marinade contaminated by fomites. So it's probably not a high virus density on a single fish's surface, but it is all over the fish, and on all of the fish.
So on the processing side, it's quite possible that a coronavirus infection, especially if multiple workers in a shift are infected, leads to a high number of contaminated fish. These fish are transported at around 0 °C, for which the virus might survive several days. Image
Now, in the seafood market, processing the contaminated fish is the most possible way of infection. Again, the body liquids of a contaminated fish are spread all over the workplace. Possibly, it's even many contaminated fish from the same delivery!
If they don't take the most meticulous hygienic precautions at the seafood market, it's possible that a worker processing a batch of contaminated salmon is at some point getting in contact with the fomites and gets infected.
Some word to hygiene and culture. It's not "these wetmarkets" or the generally low hygienic standards in China. It's sufficient if the worker wasn't wearing gloves, or didn't wash hands for 30 seconds afterwards. I have seen this many times on fish markets in the West, too.
Back to the fomites. Shouldn't customers all over the world get infected. Depends. If the density of fomites is low on the surface of the fish, a infection is less likely as the viral load is low. A single contact with a low density of fomites gives less likely an infection.
However, multiple contacts with fomites in such low density give more likely rise to an infection. So this explains why it appeared in the seafood market.

But what about other countries and places?
In a country where no case tracing is possible because community spread is ubiquitous, it's very hard even to discover the origin of the infection. So something like this will only be discovered in places with low case numbers likely.
I focused earlier on on Chile because it seemed the most likely origin due to their high market share in China. The numbers do not account for wild caught salmon, though, and season just started in May in the northern hemisphere. So another possible origin: Alaska.
Alaska relies on seasonal workers, which might import and spread the disease. Seasonal workers have usually bad working conditions too. And we've seen pictures of no adequate hygienic equipment. . Image
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