As a rule, the following applies to infectious diseases: anyone who has recovered remains protected from the pathogen for some time. But with Corona there are more cases of renewed infections, some with severe symptoms. What does this mean for the development of the pandemic?
In recent weeks, there have been an increasing number of patient reports from Belgium, Sweden, the Netherlands, the United States, Ecuador or Hong Kong who have already encountered a second corona virus infection. But is it really a reinfection? The genetic code of the virus also plays an important role.
Case from the USA: severe course after reinfection
This case caused uncertainty as early as mid-October: in the United States there was a 25-year-old coronary patient who had been in good health for a long time a second infection with the SARS-CoV-2 pathogen It has been demonstrated.
Rise of New Infections: The animation shows a terrifying corona trend in neighboring countries to Germany. (Source: t-online.de)
With the second infection, the young man not only showed symptoms such as fever, headache and cough. He also had to be taken to the emergency room and ventilated a few days later.
The discovery of this specific case, which was described in a study, shows that immunity after infection is not absolute and multiple infections are possible, the authors write. The analysis was submitted to “The Lancet” magazine. In addition, the patient’s second disease was more severe than the first, writes the team led by researcher Richard Tillett.
What role does the genetic code of the virus play?
Genome analysis of humans from the USA showed that the corona pathogen in the second infection was genetically clearly different from the pathogen in the first infection. “These results suggest that the patient was infected with SARS-CoV-2 on two separate occasions with a genetically different virus. Therefore, previous exposure to SARS-CoV-2 may not guarantee complete immunity in all cases,” writes the authors of the study in “The Lancet”.
Already at the end of August it was reported from the Netherlands what tests had shown on patients with multiple infections: the genetic code of the second infection is different from that of the first. Each SARS-CoV-2 infection has a “unique genetic signature,” said Dutch virologist Marion Koopmans, according to a report by “Ärzteblatt”.
Koopmans is therefore not surprised that a new infection is possible: “We know from other respiratory infections that you are not protected for life, and we do not expect this from Covid-19”.
Multiple contamination would affect vaccination programs
May the Coronavirus So connect it several times in a row? This would have implications for future vaccination programs and forecasts for the duration of the corona pandemic. Especially in times of rapidly increasing numbers of infections, the spread could pose even greater challenges to the healthcare system.
But what exactly is the state of research on multiple infections?
Observed cases of patients who changed after recovering from COVID-19 infected with the corona virus a second time immediately after the onset of the pandemic. One woman’s case became known in Japan in late February, and shortly thereafter researchers reported in the magazine “Jama” that several people had been infected for the second time in China. Similar cases have now been documented, for example, in Hong Kong, Belgium, Sweden and the Netherlands.
WHO assumes individual cases
How long immunity lasts after an infection and how its duration is related to the severity of the course of the disease, science cannot yet answer with certainty.
The World Health Organization (WHO), however, underlines an important point: Since some 25 million people worldwide have now been infected with the coronavirus, the reports are likely isolated cases.
Temporary immune protection against viral diseases
It would be an indication that a SARS-CoV-2 infection does not behave completely differently from other viral diseases. Experience so far – including with SARS, MERS and influenza – teaches that anyone who has recently recovered from a pathogen has formed appropriate antibodies. The immune system can then fight off a new infection, at least for some time.
Furthermore, it is not yet clear to what extent general conclusions can be drawn from cases such as the current one in the US. The authors of the study presented in “The Lancet” also refer to this.
Covid 19 patient on a stretcher: the question of whether people can be infected with Corona several times in a row cannot be resolved with certainty. (Source: Maxim Shemetov / Reuters)
Longer protection is conceivable
The greatly simplified summary of the results of the current study also reads: Longer protection is at least conceivable. Our immune system has various means of getting rid of invading pathogens as quickly as possible. When it comes to new pathogens, such as the SARS-CoV-2 coronavirus, the body is unprepared and cannot defend itself quickly enough.
However, the immune system is not inactive: if the virus has penetrated into the cells of the body, it forms, among other things, the so-called T-Killerzellen, which are specifically geared to the new pathogen. They destroy the cells of the body where the virus has lodged. B lymphocytes (B cells for short) produce antibodies which bind to the pathogen and thereby render it harmless.
If the virus is defeated, these defensive weapons gradually diminish. However, the body is prepared for another attack of the virus. Among other things, it has formed memory cells that can build a protective wall of killer cells and B cells relatively quickly. In addition, antibodies often remain in the blood. This makes it difficult or even impossible for the pathogen to cause a second infection.
Easiest course possible with a second infection
This type of protective mechanism also works in principle with SARS-CoV-2. The only question is whether and for how long the protective wall is strong enough to repel the virus in the event of a second attack. This has not yet been clearly clarified. It could also be that the course of a second infection is at least easier or that one is no longer contagious, says Carsten Watzl, general secretary of the German Society of Immunology.
“The level of knowledge is controversial,” says Uwe-Gerd Liebert, director of the Institute of Virology at Leipzig University Hospital. It is clear that, more than six months after the onset of the pandemic, not much is known about recurrent infections after an infection. There are still no studies keeping an eye on people after an infection for years – after all, the virus has only been known for about eight months.
The role of antibodies is still unclear
Some time ago, the investigation caused uncertainty. They had shown that some antibodies directed against the virus disappear from the blood within a few months after an infection, or in some people they are not even detectable in the first place.
Watzl warns against jumping to conclusions. It is not clear how many antibodies are needed for effective protection.
Covid-19 test: are you immune or can you be reinfected after an infection? (Source: Christian Ohde images / imago)
Memory cells detected in Covid patients
Some studies on T and B lymphocytes had aroused some optimism among experts. For example, the Swedish researchers report in the journal “Cell” that in the case of large-scale coronary infection, the so-called Memory cells T. under construction.
Furthermore, the researchers recently wrote in the specialized journal “Nature” that they have specific information in all the samples examined by Covid patients cured. T cells. I found.
A US preprint study concluded that people had persistent memory cells in their blood after a mild course of the disease. All of this could indicate that there is some immunity that could prevent reinfection.