Comparison of the SARS-CoV-2 viral genomes showed that we are talking about re-infection after almost two months, since the two strains, in particular, differed in ten nucleotide positions in several genes.
Information that re-infection with SARS-CoV-2 is possible, although extremely rare, is no longer news. About 10-20 such cases are known in the world (and we wrote about some earlier). According to Rospotrebnadzor, there have not yet been patients with repeated Covid-19 in Russia. At the same time, how long antibodies to coronavirus persist is still not exactly clear.
According to a new study by scientists from Nevada (USA), published yesterday in the journal The Lancet Infectious Diseases, those who have recovered from Covid-19 can definitely face the virus a second time - and there is a risk that the infection will be more severe. “Previous exposure to SARS-CoV-2 does not guarantee the development of immunity in all cases. All people, regardless of whether or not they have been diagnosed with Covid-19, must follow the same precautions to avoid infection. The consequences of re-infections may be important for the development and use of a vaccine,”explained the authors of the work.
Meanwhile, in the Netherlands, an 89-year-old woman died yesterday after being diagnosed with Covid-19 for the second time. She became the first person in the world to die from re-infection with the coronavirus. Doctors reported this in an article published in Oxford University Press.
“The women suffered from Waldenström macroglobulinemia (a slowly developing disease of a tumor nature, one of the types of lymphomas. - Ed. Approx.) And underwent B-cell depletion therapy (a functional type of lymphocytes that play an important role in providing humoral immunity. - Ed. Approx.) … The patient presented to the emergency department with fever, severe cough and lymphocyte count 0.4x109 / L. The test for SARS-CoV-2 was positive. Five days later she was discharged. In addition to permanent fatigue, the symptoms completely disappeared. Two days after the new course of chemotherapy, 59 days after the first infection, the patient had a fever, cough and shortness of breath. On admission to the hospital, her oxygen saturation was 90%, and the respiratory rate was 40 per minute. The test for SARS-CoV-2 was again positive,”the authors of the report write.
On the fourth and sixth day, blood was taken from the woman for testing for antibodies: both tests were negative. On the eighth day, her condition worsened, and two weeks later she died.
The researchers compared viral genomes using multiplex PCR (simultaneous amplification of multiple regions of template DNA) and nanopore sequencing.
“The two strains differed in ten nucleotide positions in the genes ORF1a (4), ORF (2), Spike (2), ORF3a (1) and M (1), the sequences were not clustered in the phylogenetic tree. Although we did not have PCR negative samples between episodes, with an average estimated mutation rate of SARS-CoV-2 of 33 nucleotides per year (or five to six nucleotides in two months), it seems that we are talking about reinfection. " the doctors said.
They emphasized that the patient's immunity was weakened due to Waldenstrom's macroglobulinemia. Since she was undergoing B-lymphocyte depletion therapy, her humoral immunity decreased. However, according to doctors, it has already been shown that such treatment does not necessarily lead to a life-threatening disease, because the innate immune response and T-cell immunity may be enough to fight the coronavirus infection.
“It is believed that reinfection occurs after a decrease in antibody titers and a weakening of immunity. Although a recent population-based study in Iceland showed that antibodies to SARS-CoV-2 did not drop until four months after infection, re-infection with “seasonal coronaviruses” (HCoVNL63, HCoV-229E, HCoV-OC43 and HCoV-HKU1) occurred after six months after the first. Our patient and patient from Nevada (a 25-year-old young man who contracted Covid-19 in April and June 2020. You can read about him here. - Ed.) Had an “early” re-infection (within two months). At the same time, the American developed antibodies after the second episode. Our patient did not have them already six days after the infection was re-identified,”summed up the authors of the report.
Research on reinfection cases is limited due to the amount of work, scientists say. Those susceptible to SARS-CoV-2 can still test positive for several months without getting sick. Therefore, samples of the virus strains of both "episodes" of Covid-19 are needed in order to be able to confirm whether they are different and whether it is worth talking about re-infection.