Science Review: will the new coronavirus be contained or continue to spread?

Author: as of 11:56 on February 4, biotech king has diagnosed 28064 cases in China (including Hong Kong, Macao and Taiwan), died 564 cases and cured 1165 cases On January 29, Japan, which withdrew 565 overseas Chinese in three batches, was the country with the largest number of overseas Chinese from China Novel coronavirus (2019-nCoV) that has been ravaged by Wuhan has been provided by scientists with an unexpected opportunity In order to avoid the spread of the virus in Japan, officials from the Ministry of health, labor and welfare of Japan screened every passenger who returned for symptoms of the disease and tested them after they arrived in Japan "Eight of them were positive, but four of them were completely asymptomatic," said Hiroshi nishiura, an epidemiologist at Hokkaido University This is a dangerous signal for epidemiologists who are trying to figure out what the consequences of this rapidly spreading epidemic will be for mankind As the findings in Japan show, if many infected people are not noticed, it will greatly increase the difficulty of controlling the epidemic As of February 4, there were more than 20000 cases and 427 deaths, and mathematical modelers have been scrambling to predict the next step of the virus, the possible losses it may eventually cause, and whether isolating patients and restricting travel will slow the spread of the virus But to make confident predictions, they need to know more about how far the virus spreads, how much it infects people, and whether asymptomatic people can still infect others China is in a comprehensive battle to control the virus, and has actively shared information and data related to the virus "Countries with only a small number of cases, such as Japan, can also publish important data," said Preben aavitsland of the Norwegian Institute of public health It is now the responsibility of all countries receiving cases to gather as much information as possible " So far, because of limited information, scientists are trying to map the possible path of the virus, weighing each possibility to determine the consequences Marc lipsitch, an epidemiologist at the t.h.chan School of public health at Harvard University, said: "at this stage, it is important to have clear scenarios and evidence to support and oppose it, that is, the virus is under control or not Because it allows people to better plan for the next step " Scenario 1: the most optimistic scenario for the containment of the virus is that 2019 ncov is still largely confined to China, where 99% of the confirmed cases so far have occurred (as of February 4, 195 cases have been reported in 24 other countries) Robin Thompson, a mathematical epidemiologist at Oxford University, UK, said: "it is clear that there is a large-scale spread in China, but there is no evidence of any substantial interpersonal spread in other places, and the risk may not be as high as some models predict." If there is no sustained transmission in other countries, and the isolation and other measures taken by the Chinese government begin to reduce the number of infected people, the risk of transmission may gradually decrease, and the virus may eventually be eliminated This was the case with the outbreak of SARS in 2003, which ended after less than 9000 cases The World Health Organization last week declared the outbreak a public health emergency of international concern At a press conference, director general tedros adhanom ghebreyesus called on his team to take the approach in the Ebola epidemic, which is to fight the disease at its source and try to prevent it from gaining a foothold elsewhere "Focus on the 'epicenter,' and if you have more than one epicenter, it's chaos," ghebreyesus said Marion Koopmans, an epidemiologist at Erasmus medical center in the Netherlands, said that as long as the first cases are detected and isolated early, it may not be difficult to control the virus in a new place, as long as the virus is not highly infectious "In more than 200 cases outside China, we don't see it growing," Koopmans said If this pattern stays the same, it is likely to weaken " She and others suspect that climate may help Influenza usually spreads only in winter, attacking the north and South at different times If the same is true for 2019 ncov, its spread in the northern hemisphere could start to slow in a few months "This is a big question mark that we are currently trying to assess," said Joseph Wu, a modeling engineer at the University of Hong Kong But is containment realistic? Alessandro vespignani, an infectious disease modeling engineer at Northeastern University, said: "success depends in part on whether asymptomatic people can spread the virus People without symptoms are hard to find and isolate, so if they can spread the disease, 2019 - ncov will be hard to stop in China But if asymptomatic transmission is rare, isolation can have a significant impact " So far, it's hard to make sense of the problem Some data from Chinese scholars seem to support asymptomatic transmission, but there is no clear evidence On January 30, the New England Journal of Medicine published a widely reported article describing a Chinese businesswoman who caused four cases in Germany before she fell ill But it was clear that before the paper was published, the researchers did not contact the woman who had returned to China In a later telephone interview, she said she had some symptoms while in Germany (for details, please read: Science: asymptomatic people are spreading the virus?) In a follow-up report released at a press conference on February 4, the researchers noted that some of the patients they studied were infected with the virus even if their symptoms were mild "It's almost as bad as asymptomatic transmission," said Christian drosten, a virologist at Charite University Hospital in Berlin "Patients with mild symptoms are less likely to seek medical help or even stay at home, which gives the virus a chance to spread in large numbers Scenario 2: the virus continues to spread According to the current situation, many researchers think that the time to control the virus is not good "As the virus continues to spread in China and the risk of spreading to other countries increases, we may see it spread in other countries sooner or later," aavitsland said So far, there has been no sustained spread outside China " But lipsitch expects that to change: "if there is no sustained transmission in two to three weeks, then I would be shocked by more than 200 cases outside China." If the virus really spreads around the world in a pandemic, then these questions will be urgent: how many percent of the population will be infected? How many of them will be critically ill or dead? Severe cases put forward higher requirements for the medical system, and hospitals in Wuhan have been overwhelmed, leading to greater fear and confusion in daily life A deadly pandemic could force the world to make tough choices about fair access to medicines or vaccines, if available Aavitsland said it could also lead to extensive restrictions on domestic travel, similar to those already in place in China On the other hand, if 2019 ncov is similar to the common cold or mild influenza, the spread of the virus will not be so worrying The existing travel ban may be lifted Understanding the severity and mortality of any new pathogen is a challenge In 2009, when a new influenza virus emerged and triggered a pandemic, many people worried that it might be an annoying variant It took months to determine that the new virus caused about one in ten thousand deaths So far, the mortality rate of known cases of 2019-ncov is about 2% Some reports say that 20% of infected people have serious diseases However, these figures may ignore the fact that thousands of people with mild symptoms, such as sore throat or low fever, have never sought medical help and may not even know they are infected with 2019 ncov Many people may not have any symptoms at all "So the disease that looks terrible may be just the tip of the iceberg," lipsitch said Four Japanese evacuees without symptoms are a good example Studies published in China have also reported cases with few or no symptoms What is missing, lipsitch said, is a large study in China He suggested that some tests could be used for this purpose in a place with many cases (China's current recommendation is to test only those with obvious symptoms ）If 2019 - ncov really becomes a pandemic, humans may be affected by it indefinitely After widespread transmission, the virus may catch on in people, and like the four other coronaviruses that cause the common cold, it occasionally causes new outbreaks No one can say how many deaths and diseases it will cause Thankfully, scientists are gathering and sharing information at a record rate "Over time, we will know more about this new virus and we can do better," vespignani said But the beast is moving too fast! " Jeni turtle