Sp.005 关于新冠肺炎的一切


Hi, I’m Songlei Wu, the producer of PaperClip. TV Anchor: Now let’s focus on the outbreak… (Pneumonia in Wuhan Caused by Unknown Reasons)
Wu: Just like you (Pneumonia in Wuhan Caused by Unknown Reasons)
PaperClip has always been paying attention to (Pneumonia in Wuhan Caused by Unknown Reasons)
the sudden outbreak of pneumonia caused by the novel coronavirus In this video, we will explain how everything has unfolded. How it started, spread and infected. Let’s get started. (TV noise) (electrocardiogram noise) Part 1: Infection First, we need to know how viruses infect patients. There has to be corresponding receptors on cells so that viruses can get in. For example, the common receptors of HIV are CD4 proteins. Usually found on the surfaces of immune cells in blood. So, HIV can be spread by blood, and there’s no need to worry about airborne HIV transmission. the receptors of this novel coronavirus are the same as those of the SARS virus That is angiotensin-converting enzyme 2 (ACE2). This means if the virus is to infect humans, it needs to contact cells with such enzymes, to bind to the receptor. Apparently, we have many such cells exposed in the air: Mucosae. The purpose of mucosae is to secrete mucus and maintain moisture. On our lips, eyelids, in nasal and oral cavities, There are a lot of mucous cells. When coronaviruses contact your oral mucosa in some way, And bind with the receptors, infection starts. To help you understand what happens next, We simplified the general process. First, the coronavirus envelope merges with the cell membrane, and releases virus genetic material, a single strand of RNA. This kind of RNA can be directly used as messenger RNA (mRNA). Which fools the ribosomes in cells into generating RNA replication enzymes (RNA replicase). RNA replicase then generates negative RNA strands according to the virus RNA. Negative RNA strands, along with the replicase, then generates more virus RNA segments and positive RNA strands. The various virus RNA segments generate various protein structures with the help of ribosomes. (Protein Shells) Finally, these protein shells will combine with RNAs to generate new coronavirus particles. Secreted outside the cell by Golgi apparatus, infecting new cells. Each infected cell will generate thousands of new virus particles, Which spread to the tracheae, bronchi And eventually the alveoli, causing pneumonia. After the infection, Spreading is not a hard job. Saliva secreted by three pairs of your salivary glands will be mixed with the respiratory secretions from your throat and other parts of your body, allowing your coronavirus-laden saliva to transmit into the air by your sneezes and coughs, contacting others’ mucosae. Mucosa infection, airborne transmission. That’s why the novel coronavirus is so easily transmitted. On December 8, 2019, A patient from Huanan Seafood Wholesale Market was admitted to hospital because of his 7-day-long fever, coughing and dyspnea (labored breathing). 5 days later, His wife, who had never been to the seafood market, was also admitted into hospital because of unknown reasons. On the New Year’s Day of 2020, Huanan Seafood Wholesale Market was shut down. On January 2nd, 41 patients were diagnosed with novel pneumonia. Back then, citizens who were preparing to celebrate the Lunar New Year didn’t know that an outbreak potentially infecting thousands had started. Part 2: Spreading In this paper published on the Lancet on January 24, we get to know the particular cases of those earliest diagnosed 41 patients. Up to January 22, 28 of 41 patients have been discharged, 6 died. Fever and coughs are the most common symptoms. From infection to dyspnea (labored breathing), it took 8 days on average. In early stage of pneumonia, there was apparent indication of human-to-human transmission. (“Exposure History of Huanan Seafood Wholesale Market”: blue=no exposure, pink: exposed, Dec 31 label: “epidemiological alert”, Jan 1 label: “market closed”) Among these 41 persons, 14 of them had never been to Huanan Seafood Market. On January 24, another paper studied a family from Shenzhen who traveled to Wuhan on December 29. Male patient with the earliest symptom onset started to have fever and diarrhoea 4 days after arriving in Wuhan. 3 days later, his wife and parents-in-law all developed fevers and started coughing. On January 5, the whole family returned to Shenzhen 4 days later, his mother, who had not been in Wuhan, felt lethargic. Eventually, in this family of 7, 6 were positive diagnosed with novel coronavirus pneumonia, including the son with no visible symptoms. Coronavirus spreads easily among family members with intimate contact. First, sneezing discharges more than 10,000 droplets, flying up to 8 meters (~9 yards). And then coughing discharges 1,000 to 2,000 droplets up to 6 meters (~6.5 yards). To top it off, even calm talking discharges about 500 droplets per minute. This is what it looks like 0.34 seconds after you sneeze. coloured green are the trajectories of large droplets above 100 µm They are heavy and drop to the ground within 10 seconds. coloured red, however, is the cloud of smaller droplets They quickly evaporate and diminish in size to become dry droplet nuclei. Coronaviruses, enveloped by epithelial cell proteins, drift in the air and make contact with others’ mucosae. This paper published on January 30 Further analyzed data from the earliest 425 diagnosed patients in Wuhan In this diagram, x-axis is days from infection to symptom onset, y-axis is relative frequency. We see that most patients show symptoms within 7 days, and the average incubation period is 5.2 days. Now we know that of the 295 patients diagnosed before January 11, 2020, Only 45 had visited the Huanan Seafood Market. In addition to that, 7 medical workers were diagnosed. But it’s 10 days later that people realized they should wear masks. Part 3: Masks (TV: Novel Coronavirus Pneumonia: What’s the Situation? National Health Commission Senior Expert Committee Lead, Nanshan Zhong)
From January 20, 2020, Masks have become a scarce resource.
(TV: “It is certain that we have human-to-human transmission.”) It seems that wearing masks is certainly a good idea. The multi-layered structure of a mask can effectively block large particles, and nanometer-scale particulates adhere to the fibers by static. Now, if we plot particle diameter on the x-axis, and the filtration efficiency on the y-axis, The filtration effects of these masks exhibit as U-shaped curves. We can see that the hardest particles to filter Are the ones around 0.3 micrometers. That’s why most masks are tested with 0.3 µm NaCl (table salt) as a performance indicator. Masks that filter more than 95% are “N95”. Of course, N95 is the best in filtration performance. But take even the worst ones, gauze masks, for particles more than 10 micrometers across, or around 1/10 the diameter of human hair, measure a filtration efficiency of nearly 80%. (Sneeze) So how big are droplet nuclei? According to this paper published in 2007, 82% of droplet nuclei discharged from coughing measure 0.74 to 2.12 micrometers across. So to protect against most droplet nuclei, A regular medical mask is enough. And in a randomized clinical trial with more than 2,800 US influenza health care workers, Flu infection rates of those who wore N95 masks and regular medical masks actually showed no significant difference. (Gauze mask)
So, (Sponge mask)
don’t care too much about complicated mask types. (Cotton mask)
don’t care too much about complicated mask types, (Surgical mask)
mask brands, and standards from various nations. (Medical mask) (Medical mask)
What’s more important than whether you wear N95 is What’s more important than whether you wear N95 is did you wash your hands? Because your hands likely carry live coronaviruses Take SARS virus as an example (“Research on the Survival and Resistance of SARS Virus on Outdoor Environmental Objects”, Epidemiology Research Institute, Academy of Military Medical Sciences)
In this research by the Academy of Military Medical Sciences, they found that SARS viruses can live at least 2 days on glass, plastic, and metal. They spread by tiny droplets and linger everywhere Then your hands might touch them And when you rub your eyes and pick your nose, viruses will contact mucosa cells and complete the infection. So, wash hands, and take your time. Part 4: Courage (Part 4: Courage)
The last question is: how many more will die? This is a chart from January 11 to January 31 counting diagnosed and dead patients across China. If we divide the total death count by the total diagnosed count, We get roughly a 2% death rate for diagnosed patients. But this calculation is inaccurate. From the data of the earliest 425 diagnosed patients, we know the virus has a mean incubation period of 5.2 days; 4.6 days on average from symptom onset to hospital visit; 4.5 days on average from hospital visit to hospitalization; 3.5 days on average from hospitalization to ICU (intensive care unit) admission; assuming 3 days from ICU admission to death, the whole process takes 21 days. If we assume only 3 days from the first hospital visit to a positive diagnosis, then it is 8 days between diagnosis and death. So a patient who died on January 31 would be diagnosed around January 23. If we take the 124 dead from Hubei province from January 29 to 31, and divide that by the 279 diagnosed from January 21 to 23, we get a whopping 44.4% mortality rate. But because medical resources in Hubei province have been overstretched and a positive diagnosis is difficult, many elderly patients could only be diagnosed after developing serious symptoms, giving us a biased mortality rate. In comparison, national data excluding Hubei province is closer to reality. 3 patients died in all other provinces in China from January 29 to 31, divided by the 260 patients diagnosed from January 21 to 23, gives us a mortality rate of around 1.1% and is indeed not that high. From this rate, if we extrapolate the actual number of infected patients in Hubei province from January 21 to 23, it wouldn’t be 279 infected, but rather, 10,700 infected. Of course, this is still a very rough calculation with a small sample size, and not necessarily accurate. But with improved data in the future, the mortality rate will become increasingly clear. After the outbreak, many institutes have published estimated R0 values for the novel coronavirus, most of which are between 2 to 3. R0, or basic reproduction number, measures the average number of individuals a single patient infects, with no intervention. The R0 of novel coronavirus is between 2-3, meaning that each infected individual transmits the virus to 2-3 other people. That is how the pneumonia broke out in the early stage. With strong external intervention, however, this average propagation number will start to go down For example, the 2003 SARS outbreak had an R0 of 2.9 at the onset, which then oscillated between 2.0 and 3.5, and finally decreased to 0.4 until it completely disappeared. For the novel coronavirus pneumonia, it will likely be similar. The outbreak has all of us anxious now, so just remember, bad things happen all the time. In the past few years in China, 88,000 died from flu-induced respiratory diseases each year on average, 63,000 died from traffic accidents, 38,000 died from safety incidents. As we leave home and go to construction sites, offices, and production lines, risk is already there. Of course, we should minimize the probability of those things to the best extent But we applaud courage because mankind has always chosen to do the necessary despite the risks. Finally, let’s take a look at the protagonist of this outbreak: this 0.1-micron deformed orb of a thing. Scary? We know its RNA sequence, know its infection mechanism, transmission dynamics, clinical exhibitions and mortality rate. It’s not that scary really. If we are so scared of this thing that we lock down the neighbor from Wuhan, that we attack strangers in need of help, that we scare everyone speechless in the name of preventing rumors, that would be actually scary. Round of applause to mankind and courage, and to everyone still working hard. Let us all have more courage for 2020. Bye-bye. [Music]

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