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If the information is correct, virologist Christian Drosten from the Charité in Berlin was right: without countermeasures, he assumed, the Sars-CoV-2 coronavirus would spread exponentially until between 60 and 70 percent of the population were infected, he said. . Beginning of the year. There is now evidence that this may have happened in the Brazilian city of Manaus.
There it was not possible to roll back the pathogen. As a result, the virus was so rampant that the population may be approaching or already reaching what is known as herd immunity. Sars-CoV-2 is no longer spreading as strongly in the 1.8 million city of Manaus because up to two-thirds of the population have already been infected, the researchers report in an assessment that has yet to be professionally tested.
Coronavirus: Coronaviruses are a family of viruses to which the Sars-CoV-2 virus belongs, which is currently very widespread throughout the world. As it initially had no name, during the first weeks it was called the “new coronavirus”.
SARS-CoV-2: The WHO named the new coronavirus “Sars-CoV-2” (“Severe acute respiratory syndrome” Coronavirus-2). The term refers to the virus that can cause symptoms, but not necessarily.
COVID-19: The respiratory illness caused by Sars-CoV-2 was named “Covid-19” (Coronavirus-Disease-2019). Consequently, Covid-19 patients are people who carry the Sars-CoV-2 virus and show symptoms.
Ester Sabino’s team from the University of São Paulo Institute of Tropical Medicine analyzed more than a thousand samples from blood donors that had been delivered since February 2020. They discovered antibodies against the new coronavirus in 44 percent of the samples. As the amount of antibodies decreases over time, the researchers estimate that 66 percent of donors were actually infected.
However, the study has some weaknesses: blood donors are not representative of the population. Furthermore, the level of antibodies recorded by the researchers is more than double that of a previous antibody study in Manaus in late May.
Many dead despite the young population
However, if the population were truly the first in the world to achieve herd immunity, the price was high: According to projections, Sabino and his colleagues assume that 0.28 percent of all those infected in the city died. That corresponds to more than one death in every 400 people who carried the virus.
Since not all city residents were infected, the researchers estimate that, on average, one in every 500 residents had to die from Covid-19 to achieve the immunity that has now been determined. In more conservative calculations they arrive at a death with less than 800 inhabitants.
To put it in perspective: in Munich, which is heavily affected by the virus by German standards, 223 deaths have so far been recorded in around 1.5 million inhabitants. That’s roughly 15 out of 100,000 people.
The population of Manaus is significantly younger than in industrialized countries. The risk of a severe or even fatal course of Covid-19 increases significantly after the age of 60. In Manaus, only six percent of people fall into this risk group, in Germany it is about 20 percent.
“Herd immunity through natural infections is not a strategy, but a sign that the government has failed to control an outbreak and has paid for it with loss of life,” tweeted immunologist Florian Krammer of Mount Sinai Hospital in New York. (more on the question of whether herd immunity is a worthy target in the pandemic, read here).
Suddenly there was a great demand for coffins
The first corona case in Manaus occurred in March. Although people began to maintain a greater distance from each other at that time, for months it was not possible to contain the spread of the virus. The reasons for this have yet to be conclusively clarified. Experts suspect that cramped living conditions, poor water supplies and crowds in local transportation have fueled infections.
In March, the number of deaths in the city rose from 20 to 30 a day to more than 100 in just a few weeks, the British Daily Mail reported. Demand for caskets multiplied. Some of the dead were stored in refrigerated containers because the gravediggers were unable to follow them. The images show fields in which a new grave is lined below. There was talk of mass graves.
However, since May, the number of confirmed corona infections and deaths in Manaus has dropped significantly again, with no obvious explanation for this. Sabino and his team now see the many positive antibody tests as a clue, but they don’t rule out that changes in behavior played a role as well.
It is not a coincidence that the value of two thirds of the immune people in a population is repeatedly cited as the limit for the exponential spread of the coronavirus. Without countermeasures, each person infected with corona infects around three people with the virus, who in turn infect three new people.
This exponential spread ends as soon as each infected person only infects one other person. This is the case when two out of three people who could potentially be infected by an infected person already had the virus and are immune.
There is no indication that the virus has become any more harmless.
“Because of the way the pandemic unfolded in Brazil, I immediately believe that herd immunity might be possible in some regions,” Krammer writes. However, more research must now show whether the protection actually exists. Experts hope this will also provide information on how long once infected people remain immune.
Also in Germany, it is currently discussed why the proportion of deaths among those who tested positive for the virus Infected has decreased. The idea is circulating that the coronavirus may have changed and become more harmless. The Robert Koch Institute (RKI) considers this unlikely in its status report on Wednesday.
The low case mortality in Germany is due to the fact that many people with mild symptoms are now increasingly being examined and there are many young people among those infected. “If more and more older people are re-infected, it will lead to more serious cases and deaths,” according to the RKI. It is still important to prevent this.
