Nature: when did the epidemic peak?

Authors: Although the novel coronavirus pneumonia (COVID-19) epidemic continues, according to the National Health Committee data, by the early morning of this morning, 56 new confirmed cases in Hubei except the region have been declining for fourteenth consecutive days Since the outbreak of covid-19, people have been concerned about when the epidemic will peak Yesterday, academician Zhong Nanshan, head of the high-level expert group of the national health and Health Commission, said: "it is expected that the number of newly confirmed cases will reach a peak in late February, but this is not necessarily a turning point, it depends on the rework situation However, my personal prediction is that there should be no more high incidence, and governments around the world have taken very strict isolation measures for rework " Although the peak prediction is instructive, some researchers warn that it is difficult to achieve accuracy, especially when the data used in the model is incomplete "If you revise your forecast every week to say that the epidemic will peak in a week or two, you will be right in the end," said Brian labus, who works on disease surveillance at the University of Nevada Optimistic assumption: on February 11, academician Zhong Nanshan said that the epidemic may peak at the end of February The situation has improved with government controls such as travel restrictions and extended holidays, although he admits it is still a "difficult time" for Wuhan So far, more than 70000 people have been diagnosed with covid-19 At least one model is in line with academician Zhong's prediction Researchers at the London School of hygiene and tropical medicine predict a peak at any time now Sebastian funk, a statistician who modelled the epidemic, said the prediction was based on an estimate that before the travel restrictions were introduced on January 23, an average of 1.5 to 4.5 people were infected by an infected person in Wuhan, a measure known as the number of virus effective reproduction (R) Funk estimates that about one million people (about 10% of Wuhan's population) will be infected during the peak period On February 12, funk published the analysis without peer review on his Institute's website But he said that since the work was completed, the decline in new cases and deaths in Wuhan suggests that infection may have peaked (14000 new cases were reported on 13 February, but the increase was due to changes in the way cases are diagnosed by Chinese authorities, not a real surge) The worst case scenario some researchers found was too optimistic Hiroshi nishiura, an epidemiologist at Hokkaido University in Japan, said that people in most Chinese cities started returning to work last week after a long public holiday, opening up the possibility of a new communication chain Nishiura said the model he used estimated that the outbreak would peak sometime between late March and late May He thinks as many as 2.3 million cases will be diagnosed in one day He estimates that between 550 million and 650 million people in China will be infected, accounting for about 40% of the country's population About half of these people have symptoms, nishiura said Nishiura has submitted a paper describing the model and its prediction to the prepress server medrxiv In order to make such a prediction, he said his team considered the inherent transmission potential of the new virus - the basic number of clones associated with R, known as R0, although assuming that everyone in the population is susceptible to infection, the team estimated R0 to be between 1.5 and 2 His model, he said, offers a relatively simple point because it assumes that everyone is susceptible It also reflects the view that many infected people do not have symptoms or physical discomfort and are inadequate for medical treatment "If that's the case, the number of cases reported so far significantly underestimates the number of infections," he said Gabriel Leung, an epidemiologist at the University of Hong Kong, said nishiura's estimate was feasible "The community is not immune to the sars-cov-2 virus that causes covid-19, so it will spread throughout the community," he said While these predictions sound extreme, it's still unclear how deadly the virus is, Leung said In a paper published on February 9, academician Zhong Nanshan calculated the mortality rate and found that about 1.36 people died in every 100 cases But the number may be too high because the authors did not consider less serious cases Outside China, two deaths have been confirmed in 500 cases Control measures, such as travel bans and quarantine, have no clear impact on the timing and severity of the outbreak's peak, Leung said Nishiura and funk say their models exclude these measures because their effectiveness is uncertain Many scientists say control measures may not eventually reduce the number of infections But Leung said: "by slowing the rate of transmission, it is possible to extend the time it takes for the epidemic to peak It is important to reduce the number of people infected during the peak period If everyone gets sick at the same time, the whole society will come to a standstill, the medical service will be overwhelmed and many people will die " Reference: when will the coronavirus outbreak peak? Doi: 10.1038/d41586-020-00361-5