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First or months, researchers have warned that people without any COVID-19 symptoms could still be silent carriers of the disease, making it that much harder to get the pandemic under control—and that much more important to take precautions like social distancing and wearing a mask, even if you feel fine. So it came as a surprise when Maria Van Kerkhove, the World Health Organization’s (WHO) technical lead for COVID-19, said at a press briefing on June 8 that asymptomatic transmission appears to be “very rare.” Her statement came just days after the organization directed healthy people living in areas with widespread community transmission to wear fabric face masks in public to help contain the advance of the disease. In an interview with TIME following the press briefing, Van Kerkhove said she did not mean to suggest that asymptomatic people cannot spread COVID-19. “I did not say that asymptomatic cases cannot transmit; they can,” Van Kerkhove says. “The question is, do they? And if they do, how often is that happening?” Van Kerkhove says there’s not yet a clear answer, but the WHO’s analyses suggest symptomatic individuals are responsible for most coronavirus transmission. (She also clarified during a June 9 briefing that her comments were in response to a journalist’s question, and did not constitute official WHO policy.) The WHO laid out its thinking in its latest guidance on face masks, which was circulated on June 5, and was based on a number of reports that examined COVID-19 community spread and transmission dynamics, as well as not-yet-published findings from contact-tracing reports from multiple WHO member states. Few of the cited papers explicitly examined population-level asymptomatic transmission rates. One, a preprint (i.e., not-yet peer-reviewed) research review posted to the site MedRxiv on June 4, analyzed four previous studies (two published and two preprint) that estimated asymptomatic transmission rates. The highest estimate was a transmission rate of 2.2%, suggesting “asymptomatic spread is unlikely to be a major driver of clusters or community transmission of infection.” The WHO’s guidance also notes that some studies that have found evidence for asymptomatic transmission had small sample sizes, which would make their findings less statistically relevant. In addition, the WHO said, some of these studies did not rule out alternative explanations for how some patients may have contracted the virus, like touching a contaminated surface. However, just last week, researchers from the Scripps Research Translational Institute published a paper estimating that asymptomatic individuals account for up to 45% of coronavirus cases, and noted that “the viral load of such asymptomatic persons has been equal to that of symptomatic persons, suggesting similar potential for viral transmission.” One of the study’s author’s, Scripps Director Dr. Eric Topol, criticized the WHO’s comments on Twitter, writing that “there are several studies not included in [the WHO’s] brief statement that counter the scant data provided here.” Carl Bergstrom, a biologist at the University of Washington, wrote on Twitter that the WHO’s conclusions were based on “thin evidence,” at least when taking into account what has been published publicly. Bergstrom also said the organization should have more clearly distinguished between people who are “truly” asymptomatic—those who never show symptoms—and those who may unwittingly spread the disease in the days before they become symptomatic. Topol’s study on asymptomatic transmission found that few people who test positive without symptoms go on to develop them, but studies suggest it takes an average of five days after exposure to the virus for symptoms to surface. People in this phase would be considered pre-symptomatic, not asymptomatic, but it’s difficult to tell the difference. “Even if truly asymptomatic spread is very rare, pre-symptomatic transmission is likely to be important,” Bergstrom wrote on Twitter. “We still need to wear masks and distance to avoid spreading the virus during this period, probably concentrated in days 3-6 after infection.” Van Kerkhove acknowledged that distinction when speaking with TIME after the press briefing, and added that it can be difficult to distinguish between a mildly symptomatic and asymptomatic person. Some people may not associate mild symptoms—like fatigue or muscle aches—with COVID-19, but these individuals would still technically be symptomatic and capable of spreading the virus, Van Kerkhove says. With so much uncertainty, Van Kerkhove says more research on transmission patterns and asymptomatic carriers is required. She says people should continue following public-health guidance such as wearing fabric face masks when social distancing is not possible, and should stay home if they feel unwell. Doing so, in conjunction with robust contact tracing and isolation of people with symptoms, will help keep COVID-19 spread under control, she says. “We’re not ruling anything out,” Van Kerkhove says. “We’re not saying that [asymptomatic spread is] not happening. But we’re saying more transmission is happening among symptomatic individuals. People are looking for a binary, and it’s not that.” Bergstrom was more direct. The WHO’s statement “seems to suggest that people without symptoms don’t spread COVID19,” Bergstrom tweeted. “Does this mean shoppers, students, protesters, etc., don’t need masks/ distancing? No.”

The people - oriented, people to food for the day, food to ann first, food safety, related to the national economy and people's livelihood, the responsibility is heavier than mount tai. However, in recent years, food safety incidents occurred frequently, " big head doll", " poisonous rice", " poisonous milk powder", " sprite mercury poison door", " dyed steamed bread", " lean meat essence" and other events, so that the majority of consumers into extremely nervous. In order to better cooperate with the publicity and promotion of the national food safety law, improve the food safety knowledge of the general public, enhance the awareness of food safety responsibility, prevent more food safety incidents, protect their physical and mental health and safety, so that we must cause enough attention. Today, small plaid for everyone to bring a new live fish detection event, at the table of delicious food, also can let us on the safety of their own diet plays an indispensable role! Soon the new year's day is coming, every family is busy preparing new year's products, go to the supermarket, vegetable market to buy fish is a must. However, in the past, the Beijing food and drug administration has released the Beijing food safety supervision and sampling information, including wal - mart, yonghui, Tesco and other supermarket sales of fresh fish were detected illegal substances malachite green. You will certainly ask: what is malachite green? What harm? Still can rest assured to buy fish? What is malachite green for? Malachite green is a synthetic organic compound of triphenylmethane, which is not only a dye ( pigment ) but also a bactericide. As early as the 1930 s, people found that it can kill bacteria, disease resistance, widely used in aquatic animals, is also used legally at that time. Later in the 90 s, scientists gradually found that the material is toxic to aquatic products, may cause cancer, is basically no longer used. Malachite green is now banned from being used in aquatic products or fish for human consumption in China, the United States, the European union, Canada and Japan. However, as malachite green can be used to control parasitic, fungal or bacterial infections of fish or fish eggs, and to prolong the shelf life of aquatic fish, there are still some unscrupulous traders who will use malachite green illegally and take risks at their own risk. Why is malachite green detected in live fish? As for why check out, the biggest possibility is that someone will illegally add. In fact, the illegal use of malachite green has been relatively common in China. China issued a document in 2002 as a prohibited veterinary drugs, for many years is also a key monitoring project, but still repeatedly banned. Malachite green is often found in aquatic products sold in Beijing, Fujian, Zhejiang and Shaanxi provinces. Detect malachite green, how much harm? See this news, everyone's most worried about is whether there is harm, also can rest assured to eat fish? Malachite green is a non-edible substance prohibited in food in China, only use is illegal, should be severely punished. However, the detection of not necessarily toxic and harmful, whether there is harm, also depends on the specific amount of how much, how much you eat. In fact, neither the food and agriculture organization of the United nations / world health organization joint Committee of experts on food additives ( je CFA ) nor international food safety organizations such as the international agency for cancer research ( IARC ) have assessed the food safety of malachite green, nor is there any evidence that malachite green causes cancer in humans. However, some animal experiments have found that toxic to the liver, can induce liver tumors in mice. However, the international organization of genetic carcinogens recognition principle is: generally carefully think that those who have been confirmed to cause cancer to animals, may also have potential carcinogenic harm to humans. Therefore, malachite green ban is put forward from the perspective of risk management. For this reason, China also prohibits the use of malachite green. The CDC of Shaanxi province has evaluated the pollution and dietary exposure of malachite green in freshwater fish. the results show that malachite green is common in freshwater fish and illegal use is serious. however, in terms of dietary exposure, malachite green is also a low risk to human health. Malachite green has also been detected in live fish products sold in hong kong by the hong kong food safety centre, usually in the range of 3 - 480 ug / kg, compared with 7 - 34.94 ug / kg in this exposure. The hong kong food safety centre has assessed on the basis of their test results that the intake of malachite green at that level is unlikely to have a serious impact on human health., if the international standard risk assessment method is adopted and based on the results of animal experiments, it is concluded that even if humans eat 290 kg of freshwater fish per day, the intake of malachite green will not have a serious impact on health., as for eels with a high malachite green content, even if humans eat up to 7 kg per day, it will not have a serious impact on health. By comparison, malachite green detected this time in China will not have much risk. In general, malachite green is indeed a non-edible substance, illegal addition should be severely punished, the government should strengthen supervision. However, we should also correctly understand the amount of malachite green may produce harm, rather than " talk about green change". In fact, the occasional food risk is not necessarily high. What about consumers? However, there are still a lot of people don't trust, and malachite green, after all, is not something, want to eat less as far as possible. So, what should I do? The proposal of the booklet is that when consumers buy fish and other aquatic products, they should first try to buy aquatic food from the formal places., they should not go to small stall hawkers, especially unlicensed hawkers, because they are greedy for petty gains. In addition, in the daily diet should also pay attention to balanced diet, ensure food diversity, this also can reduce the risk of poisoning. How can the naked eye tell? So, how to visually identify " malachite green aquatic products"? Inspectors said, because malachite green has high residue, used malachite green fish surface color is light blue, some by the concentration of malachite green solution soaked fish, even green grass green, can be identified by observing the fins, gills. In general, gills are bright red and do not have dirt, but malachite green solution soaked gills because of excessive blood loss and white, or because of bleeding with blood stasis, purplish red. The inspectors said that even after the use of malachite green fish death, fish scales will shine, the color is bright, as if just died, it is difficult for consumers to distinguish from the appearance, which greatly increased the probability of dead fish for sale. And no malachite green scales have no luster. Inspectors remind the public to try to soak before draft products, so that even if the fish after malachite green solution immersion, also can dilute, and try to boil through, steamed through, don't eat raw, in order to reduce the toxicity to the human body. Let's listen to the experts how to pick fish? How can I pick fresh fish? Experts from Zhejiang marine aquaculture research institute put forward four suggestions: First, fresh fish have full and prominent eyeballs, while non-fresh or frozen fish have shrunk their eyeballs. Secondly, the fresh fish meat has good elasticity and glossy section; Fresh or frozen fish through ice crystal process, protein dehydration, poor elasticity, meat loose. Third, fresh fish and fishbone are difficult to separate by hand, while fresh or frozen fish and fishbone are easy to separate by hand. Fourth, fresh fish mucus transparent, not fresh or frozen fish mucus turbidity or no mucus. These are the main indications, but also can help to see the gills, fresh gills dark red, but some frozen fish after thawing for a period of time gills will be dark red. Therefore, the farmers, want to know how to keep good fish without malachite green? 1. must pay attention to the pond health, a batch of fry raised to do " all in and out", put clean water in, don't loathe to give up. 2. at ordinary times also must pay attention to the cleaning of fish ponds 3. must pay attention to the density of breeding, density is too large, the fish is more likely to get sick. In addition, our scientific research workers can also work harder, learn from the advanced experience of the European union, to develop a safe, efficient, side-effect cost-free and populist vaccine, advance to the fish on the vaccination. Nowadays, food safety has gone beyond the traditional food hygiene or food pollution, and has been related to the food management and protection of human survival and healthy development. It is not only an economic problem but also a political problem, not only a management problem but also a technical problem. Food safety needs the participation of the whole society. food safety has become a social problem of public concern.  

A safe animal food (feed) supply helps ensure healthy animals and people. To that end, the Center for Veterinary Medicine: monitors and establishes standards for animal feed contaminants, including those in pet food, approves safe food additives for animal food use, and manages the Food and Drug Administration's (FDA) medicated feed and pet food programs.