Most of the outbreaks since the initial eradication of domestic epidemic can be traced back to the pollution of cold chain fresh goods. For example, Beijing Xinfadi Market, Qingdao Port, Tianjin Port and Dalian Port, so Sanya is no exception. Then it is very necessary to sample nucleic acid from cold chain and even live seafood, which is the scientific nature of news reports. Wipe the fish's throat? Fish's respiratory organs are gills, and there is no physiological structure of "breathing", so it is impossible for seafood just fished out of the sea to contain COVID-19. The only possibility that they are poisoned is that they are contaminated with droplets when they are handled by overseas fishermen.

So the part where they may be infected with the virus should be the fish, not the throat that has been confined. It has also been mentioned in many news reports that the sampling site includes this fish, but because the people really can't understand the throat of this fish, the current pictures and video materials are only photos of the stickleback fish by epidemic prevention personnel. Of course, this kind of funny picture at first glance is more likely to create public opinion topics and spread faster. It is prepared for frozen seafood that will die without water, such as deep-sea fish, rice grass and sage. People come out of the water and die, with their mouths closed tightly and infected with poison. For live seafood, such as Sparus macrocephalus, live sea crabs and even other live mollusks, it is much simpler. The environmental nucleic acid in seawater can be directly detected in a temporary culture tank.

I wanted to write the answer to this question yesterday, but I nodded in praise and quit with satisfaction. But there are still some ideas I want to share with you. It is necessary to detect COVID-19 nucleic acid in seafood, because we really can't rule out the possibility that some fishermen buy fish by barter or cash with overseas fishermen at sea. After all, the price of human resources in Vietnam is lower, and fishermen in Hainan may buy Vietnamese fish at a low price and sell them at a high price after landing. Isn't this much more comfortable than fishing by yourself? Then the seafood after landing can't be guaranteed not to carry COVID-19. Because the preservation environment of seafood itself is very friendly to COVID-19-humid and low temperature. Fish, shrimps and crabs that have just been fished out of the sea cannot carry COVID-19 by themselves, but people may pollute them through droplets during sorting and treatment.

Of course, the content of COVID-19 in seawater may be very low, and it is also possible to increase the number of cycles during nucleic acid detection, otherwise it may be too low to be detected. Many domestic epidemics can be traced back to cross-border cold chain transportation, and at present, we have accumulated rich experience in cold chain quarantine inspection. But how to measure live seafood and chilled seafood is really unprepared. Many people who are engaged in nucleic acid detection at the grassroots level are not medical background, and many are non-professionals who have received short-term training.

Therefore, in the future, we should draw lessons from this kind of inadequate preparation and plan in time, and summarize the scheme of nucleic acid detection for cold and fresh seafood as soon as possible, such as:

1, where should the nucleic acid sampling points of chilled seafood and live seafood be? Don't poke the throat that may be completely virus-free. Fish is not a person. Unless there is scientific evidence that there may be viruses in the pharynx of fish that die out of water.

2. nucleic acid detection of environmental samples of live seafood, seawater in temporary incubator or seawater filter, which part should be taken? The sample should undergo several cycles of PCR amplification. How to judge the CT value if it is positive?

3. How to effectively prevent fishermen from illegally diving into the sea and trading with overseas fishermen?

This requires multi-sectoral and interdisciplinary cooperation in basic scientific research, market supervision, border inspection, maritime patrol and even the navy. I believe that the problem will definitely develop in the direction of solution. Since the outbreak of the China epidemic, there have been many flaws in all aspects, but they have been quickly solved. In fact, the COVID-19 epidemic is also a test for human beings. Without it, the problems in our public health policy and implementation may never be discovered, or there may be no great motivation to correct them. But now the epidemic has appeared, many problems have surfaced, and they have ushered in changes. Specific to this seemingly funny news, we should also treat it dialectically: on the one hand, it is indeed scientific and necessary to detect the nucleic acid of the catch; But on the other hand, it can't be denied that the detection method is indeed hastily prepared, which is quite funny from the perspective of perception and scientific principle.

There are two possibilities for fishing boats to go out to sea:

1. Catch fish by yourself, so as long as the owner doesn't have it, there won't even be frozen fish.

2. The catches bought directly from overseas fishing boats may be contaminated by viruses carried by the other side, so there are two kinds of catches, frozen and fresh, frozen environmental nucleic acids. There is no problem in measuring the surface of the object that people mainly contact. No one will open the fish's mouth and get poisoned. In fact, it is not necessary to measure fresh fish, because even if it is polluted, you can't measure it, because ships put fresh fish in water tanks and often change water to keep them fresh. Strangely enough, it can be measured. Measuring the environment is more reliable.

Theoretically, all vertebrates may be infected with COVID-19 virus. But so far no cases of fish infection have been received. Therefore, fish should not be intermediate hosts in the infection chain, but only pollutants. From the sampling type, it should still belong to environmental sampling. For environmental sampling, it is necessary to estimate how long viruses in the environment can remain a threat before designing a sampling scheme. I think there is no corresponding research support for direct oral sampling of fish. Personally, it is more professional for CDC to arrange overall environmental sampling. Because the risk of packaging, hull and other environments may be higher than the risk of fish itself.

In fact, this is a bioinformatics article, which uses the existing data to make corresponding calculations and predictions, without experiments. Of course, we can't directly predict whether an organism can infect COVID-19, but we can use an intermediate molecule ace2, which is the key for COVID-19 to enter the cell. If cells have this key, COVID-19's infection may occur. Of course, the ace2 of different species is very different, so the author chooses to calculate whether the ace2 of different species can combine with COVID-19 to form a stable polymer as the detection standard.

The correct writing should be: Theoretically, COVID-19 can't infect most fish, or it is difficult for COVID-19 to infect fish. The facts are clear here. To be sure, COVID-19 will not be infected by fish. The main concern is the topic and abstract, or it is less likely to be considered from the probability. Those who think that COVID-19 may be infected with fish need to emphasize the degree of the word "possible". After all, there are two other species that may be infected. Therefore, it is generally believed that fish will not infect COVID-19. However, pollution is a very possible thing.