Not only people, but also numbers sometimes come to a sudden, surprising level of awareness. In the case of the corona epidemic, the number is seventy: Sooner or later, that percentage of the population could become infected with the corona virus, said Chancellor Angela Merkel on Wednesday in the federal press conference – as long as there are no vaccinations and no therapies. From the chancellor’s lips, the number made it into the headlines of the newspapers and the main television news.
The number has been mentioned by scientists for weeks. It results from biological mechanisms and a bit of math. The virus infects people until it is difficult to reach anyone who has not yet been infected. Mathematical models show that the number of new infections decreases significantly, and in the end a good two-thirds of the population went through a Sars-CoV-2 infection. One hundred percent is not reached because the likelihood that carriers will meet non-infected people is becoming increasingly smaller, also because a large part of the population is immune after surviving infection.
At the moment, immunologists have good reasons to believe that you can only become infected with the pathogen once and then become immune. Once the human immune system has dealt with a pathogen, it can keep it in check in the future.
The immune system’s memory usually lasts a lifetime. A pathogen can only avoid this defense if it changes so much that the immune system no longer recognizes it. Influenza and simple cold viruses are so versatile. The new corona virus, however, seems to change less. However, it is a new pathogen that humanity and thus human immune defense has never experienced. The influenza viruses that recur every year in winter, on the other hand, are often similar, so that the immune system can recognize and fight the intruders faster.
Up to 8.7 million people would have to be treated in the hospital
If what epidemiologists and the Chancellor currently foresee are true, the virus would affect around 58 million people in Germany alone. If, as the figures from China suggest, with almost a sixth of severe courses, 8.7 million people would have to be treated in the hospital. Between 300,000 and 1.8 million people could ultimately die from Covid-19. Not included are all those patients with other illnesses who cannot be treated due to the overloaded health system.
It cannot be predicted whether the terrifying number of 70 percent infected will be reached in the end. There are still many open questions regarding the new corona virus. So it may be that Sars-CoV-2 only reaches 40 or 50 percent of the population, or maybe more.
Shrugging fatalism would be the wrong reaction. This is more important than the percentage When. It is crucial to delay the spread and spread the diseases over as long a period as possible. This is the only way to somewhat limit the health consequences for those infected, but also for the economy and social life. The efforts of the government and authorities are currently aimed at this.
In the best case, the right measures will allow the corona wave to subside to such an extent that there are only individual outbreaks that can be narrowed down in a similar way to the first outbreak in Germany near Munich at the end of January. If this were successful, it would take a very long time to reach the 60, 70 or even 80 percent of the population who are infected. In such a scenario, the number of people with acute illnesses could be kept below the threshold beyond which the health system would be overwhelmed.
There are no longer enough ventilators in northern Italy
On the other hand, if the spread of the virus remains unchecked, the number of infected people would grow exponentially within a few weeks, exceed the capacities of the health system and overwhelm society. Various forces act on the shape of the contagion curve: on the one hand, human behavior. Whether the majority abides by the hygiene rules, avoids busy places, goes into quarantine as soon as one could become infected, whether schools, universities, companies with suspected cases are closed. All of this determines the speed at which the virus spreads. At the same time, the pathogen could change and become more harmless or dangerous through genetic mutations. However, nothing has indicated this since the first appearance in Wuhan.
Only one vaccine could change the total number of people infected during the pandemic. However, humanity will have to wait for this at least until the end of the year, more realistic until the middle of next year. And if the vaccine proves to be safe and reliable, the first doses will be distributed to doctors and nurses to ensure health care.
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If, on the other hand, the exponential spread of the virus continues at the current pace, with a doubling of the number of cases every four to seven days, the load limit of the German health system would probably be reached by May at the latest. Then there are likely to be several million infected people, about one in five to six of whom are so seriously ill that they need to be treated in a hospital.
At least a hundred thousand beds are permanently available in German hospitals, and more could be made available by postponing operations and other treatments. The first thing that could become a scarce good would be the ventilators that are often used for difficult courses of Covid-19. There is one of these machines for each bed in the intensive care units, a total of around 28,000 in Germany. In many clinics in northern Italy, the number of patients in need of ventilation now exceeds the number of available devices.
The number of fatalities ultimately depends on the course of the epidemic over time. The term lethality describes the proportion of those infected who die from the virus. Depending on the world region and study, mortality is currently between half a percent and five percent. This wide range is partly due to the fact that the number of people affected is not equally well diagnosed everywhere. In areas with few tests, especially minor disease courses remain undetected; mortality is then correspondingly higher among the known cases. On the other hand, lethality is also determined by how well the healthcare system can care for patients. That is why it is so important to stop the increase in new infections quickly.
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