Could it burn out after 20 percent of the population is infected?

is more than 500,000 Died worldwide at COVID-19. It’s a big tragedy, but probably not the scale I was afraid at first.. And finally, there are signs that the pandemic is shaking in places, like a lack of fuel in the engine. As a result, many governments have abandoned the blockades, allowing them to resume their daily lives, albeit freshly.

It was difficult to predict and understand the spread of SARS-CoV-2. so Diamond princess cruise shipFor example, only 20% of passengers and crew were infected when the virus was likely to spread relatively freely through the air conditioning system connecting the cabins. Data such as military ships and cities Stockholm, New York,and London It also suggests that the infection rate is about 20%. This is a much lower number than previous mathematical models suggested.

this is Speculation Whether only 20% of infections can immunize against certain viruses-well below the well-accepted herd threshold of immunity (60-70%).

Swedish public health authorities said in late April that the capital StockholmShowing signs of herd immunity– – It’s estimated that about half of the population was infected. But two weeks later, the authorities found that their antibody studies were just 7.3 Percent were infected. But the number of deaths and infections in Stockholm Instead of increasing, it is decreasing – Despite the fact that Sweden does not implement lockdowns.

The expectation that the Covid-19 pandemic could end sooner than it was initially feared was,Immunological dark matter‘Is a type of existing immunity that cannot be detected by the SARS-CoV-2 antibody test.

Antibodies are produced by the body’s B cells in response to certain viruses. However, dark matter includes a function of the innate immune system called “T-cell immunity.” T cells are produced by the thymus and when they encounter a virus-fighting molecule called an antigen, they are programmed to fight the same or similar viruses in the future.

Studies show that people infected with SARS-CoV-2 actually T cells that are programmed to fight this virus.. Surprisingly, people are never infected Also harbors protective T cells, Probably because they were exposed to other coronaviruses. This may lead to some protection against the virus-potentially explaining why some outbreaks appear to be burning out well below the expected herd immune threshold.

Adolescents and people with mild infections are more likely to respond to T cells than older people – a programmable reservoir of T cells Decline with age..

Hotspots are occurring in many countries and regions with very few cases of Covid-19. Fight the virus quickly and efficiently, Lowest mortality Among the northern European powers.

Here, the R number has risen again (reflecting the average transmission rate), staying below 1 until June 18, but jumping sharply 2.88 days later, Drop again after a few days. It may be tempting to argue that this may be because the hotspots are not close to the 20% infections found in other areas.

But there are counterexamples, especially in the elderly and immunocompromised populations. In the epicenter of Covid-19 in Italy in Bergamo, where one in four people is a pensioner, 60% of the population possesses antibodies by early June..

The same applies to some prisons. 54% of prisoners at the Trousdale Turner Correction Center in Hartsville, USA By early May tested positive for Covid-19.. And above Half of the inhabitants Some nursing homes are also infected.

Gene and environment — So how do you explain this? Can people in places with a high percentage of positive antibodies have different genetic makeup?

Early in the pandemic, there was much speculation about whether a particular genetic receptor might affect susceptibility to the SARS-CoV-2 virus. Geneticists ACE2 And TMPRSS2 Genes can affect susceptibility and severity of infection. However, previous studies have not provided compelling evidence to support this hypothesis.

Initial report from China It was also suggested that blood type may play a role, and blood type A may increase risk. This was recent confirmed A study of Spanish and Italian patients also discovered a new genetic risk marker called “3p21.31”.

Genetics may be important, but environment is also important. It is well known that airborne penetration of droplets is enhanced in colder climates. Hyperinfestation events at several meat production facilities with cold indoor climates suggest This increased the infection.. People also tend to spend more time indoors and nearby during bad weather.

But warm weather, albeit outdoors, ties people together. Indeed, June has been characteristically hot and sunny in many countries in Northern Europe, overrunning parks and beaches, and expanding rules of social distance. fluffy.. This will probably accelerate the infection and cause a new Covid-19 outbreak in the coming weeks.

Yet another factor is how interpersonal interactions affect transmission. A few Previous model People assume that people interact the same way, regardless of age, happiness, social status, etc. But it’s not. For example, young people may have more acquaintances than older people. Considering this, the threshold of herd immunity is About 40 percent.

Will Covid-19 disappear?

The widespread blockade, coupled with the responsible actions of many citizens, undoubtedly saved the spread and life of SARS-CoV-2. In fact, in cases such as Sweden where lockdowns were avoided and social distance rules were relatively relaxed, the virus took orders of magnitude more lives than its lockdown neighbors Norway and Finland.

However, lockdown alone cannot explain the fact that infections diminished in many areas after 20% of the population were infected. This, after all, happened in Stockholm and cruise ships.

However, the fact that more than 20% of people are infected elsewhere means that the T cell hypothesis is unlikely to be the only explanation. In fact, if there is a threshold of 20%, it depends on the interactions between many genetic, immunological, behavioral, environmental factors, and the prevalence of existing diseases in some communities. Applies only to.

Understanding these complex interactions is necessary to make a meaningful estimate of when SARS-CoV-2 will burn out. It is tempting to explain the apparent success or failure of public health to a single factor.

This article was first published conversation Along Paul W Frank With Lund University Joachim Rockreyf so Umea University. Read Click here for the original article..