Since the outbreak of coronary pneumonia, scientific research institutions and scholars in various countries have published various model predictions, some of which seem to be "alarmist" and attract people's attention. How should we view these predictions?
Forecasts bring warnings.
2.4 billion, which is the middle figure of three predictions on the number of global infections in the 12 report released by the Imperial College London COVID-19 Response Team in London on March 26th.
The report gives three scenarios for the number of people infected with COVID-19 virus this year: the high infection scenario and the global failure to take measures to slow down the epidemic. It is estimated that about 7 billion people will be infected, that is, almost all mankind will be infected; Under the moderate infection scenario, if countries start to take measures to curb the epidemic (including strengthening detection and social isolation) when every 654.38+10,000 people die every week 1.6 people, it is estimated that about 2.4 billion people will be infected; In the low infection scenario, if measures are taken to curb the epidemic with 0.2 deaths per 65.438+10,000 people per week, it is estimated that about 470 million people will be infected.
This research group has published many reports since the outbreak of the epidemic, which have been widely quoted. After the team released its ninth report on March 16, the British and American governments greatly strengthened their epidemic prevention policies. Some people think that the report has played a certain role.
This is Times Square in new york, USA, taken on the afternoon of March 23rd, after the New York Home Order came into effect. On March 20th, Andrew Cuomo, the governor of New York, signed an executive order aimed at more than 90,000 residents in the state/Kloc-0, stipulating that all employees in non-critical industries in the state should work from home to alleviate the COVID-19 epidemic. The executive order will take effect on the evening of 22nd local time. (Photo by Xinhua News Agency reporter Wang Ying)
The team pointed out in the report that only by taking public health measures quickly to curb the spread of the epidemic can the demand for medical care be kept at a controllable level. Now we can see that more and more countries in the world have introduced strict prevention and control measures, such as "closing cities", travel restrictions, requiring citizens to work at home or go to school, etc., all in order to "level the curve".
In epidemiology, people call the concept of slowing down the spread of the virus and then reducing the number of people who need treatment for a period of time "leveling curve". The faster the epidemic development curve in COVID-19 rises, the greater the possibility that the local medical system will be crushed.
The World Health Organization has repeatedly stressed the importance of the "leveling curve" of the COVID-19 epidemic and called on all countries in the world to take comprehensive public health measures. Howard Macher, an expert from the University of Michigan in the United States, also pointed out that historical experience shows that taking effective measures immediately will help to slow down the spread of COVID-19 and level the epidemic "curve".
There are also errors in prediction.
In the three scenarios analyzed in the London Imperial College London team 12 report, the global death toll this year is about 40 million,100000 and1860000 respectively. According to its detailed data, the mortality rates of the three scenarios are about 0.58%, 0.43% and 0.40% respectively.
According to WHO data, as of 30 10 (30 16 GMT), there were 693,224 confirmed cases and 33 106 deaths worldwide. According to this calculation, the mortality rate is about 4.8%. Why does the predicted mortality rate deviate greatly from the actual situation?
The global distribution of confirmed cases released by the World Health Organization as of 30th Central European Time 10 (30th GMT 16). (Source: WHO official website)
First of all, the number of infected people in the research model is the estimated number of all infected people, including a large number of mild patients and asymptomatic infected people. Because the symptoms of these people are not obvious, they may not be detected at all in real life.
Secondly, the mortality rate will change greatly in different periods and regions of the epidemic. China-WHO novel coronavirus Joint Investigation Report (Coronavirus Pneumonia-19) released at the end of February showed that as of February 20th, 2 1 14 of 55,924 laboratory-confirmed cases in China had died, with a mortality rate of about 3.8%. However, the mortality rate varies from region to region, with 5.8% in Wuhan and 0.7% in other regions of China. It also changes with time. The mortality rate of cases from 65438+ 10 to 10 was 17.3%, and decreased to 0.7% after February 10.
Thomas Freeden, former director of the US Centers for Disease Control and Prevention, cited a research model when discussing the epidemic situation in mid-March, and divided the mortality rate of new coronary pneumonia into three scenarios: the scenario mortality rate similar to seasonal influenza is about 0. 1%, the moderate and severe scenario mortality rate is 0.5%, and the severe scenario mortality rate is 1%.
Freeden said that the worst case scenario is that about half of the people in the United States are infected and the death rate reaches about 1%, so that about 1.6 million people will die in the United States alone. He stressed that although this is the worst case, it is not impossible.
The forecast is for reference only.
It should be pointed out that all kinds of research models have their limitations. Different models depend on different parameters and algorithms, and the results may be very different.
Jonathon Power, a professor of molecular virology at the University of Nottingham in the United Kingdom, commented on some COVID-19 epidemic models, saying that these models are based on various assumptions, and the related assumptions may often be wrong.
For example, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases under the National Institutes of Health of the United States, said on the 29th that the model showed that the COVID-19 epidemic could cause 65,438+10,000 to 200,000 deaths in the United States. This is far below Freeden's "worst case" figure of 6.5438+0.6 million deaths.
On March 29th, at the White House in Washington, USA, US President Donald Trump (left) and Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases attended the press conference. (Xinhua News Agency/Reuters)
Many experts emphasize that the results predicted by the model can only be used as a reference. If countries around the world strengthen prevention and control measures against COVID-19 epidemic, such as attaching importance to detection and strict isolation, the epidemic development trend may not be as serious as predicted by the model, and the terrible figures predicted by the above model will not come true.