Behavior is the most important factor
It was clear to Milo Puhan, head of the Epidemiology, Biostatistics and Prevention Institute at UZH, that a second wave would come. “But it came somewhat earlier than expected,” he admits. In his opinion, the rapid lifting of the lockdown in June is not to blame for this – after all, there was hardly any spread of SARS-CoV-2 in July and August. But, says Puhan, the rapid return to normality sent the wrong signal: “Many people thought in summer that the worst was already over.” This false sense of security meant that people did not protect themselves enough, or even at all. The novel coronavirus then started spreading again among young adults from September onwards, and now, in November, it is also reaching older people again. “The most important factor in containing the coronavirus is people’s behavior,” Puhan emphasizes.
Countrywide study unique in the world
The new measures taken throughout Switzerland are based among other things on the long-term study Corona Immunitas, which Puhan launched together with the Swiss School of Public Health during the lockdown in spring. Since then, Corona Immunitas has expanded to cover all regions of Switzerland. “It is unique in the world to have a record of the pandemic’s course for an entire country,” says Puhan. The longitudinal study gives information about the spread of the coronavirus in recent months, the number of people who already have immunity, and the effects of the virus in very high-risk groups and for people in exposed occupations such as grocery store or public transport employees (more on this in the video). Milo Puhan’s conclusion: “The absolute key is for everyone to protect not just themselves but also people in high-risk groups – by keeping their distance, wearing masks and washing their hands.”
No clusters in schools
Thanks to the support of the Pandemic Fund of the University of Zurich, Milo Puhan and his team were able to take a special look at the situation in the canton of Zurich. Among other things, in the Ciao Corona study he used an antibody test developed by his UZH colleague Alexandra Trkola to examine 2,500 pupils from 55 primary and secondary school classes between mid-June and mid-July to find out whether or not they had been infected with the new coronavirus. “We found that schoolchildren get infected with about the same frequency as adults,” says Puhan. But because most children develop no or few symptoms, many infections remain undetected. But that is no reason to close the schools, says Puhan. “Before the summer break, there was no clustering in classes, only sporadic infections.” The evaluation of the second phase of Ciao Corona with the same 2,500 students will show how the situation has developed in the schools in the canton of Zurich in October and November. The results are expected in December.
One antibody test for everything
An antibody test called ABCORA developed at the Institute of Medical Virology is being used in the Ciao Corona study, among others. In contrast to conventional antibody tests, which only detect one type of antibody at a time, ABCORA measures 12 different SARS-CoV-2 reactivities. The test provides a comprehensive picture that makes it possible to distinguish the stages during and after infection and – most importantly – it will also be able to detect immunity after vaccination and after infection.
Alexandra Trkola’s team has now also begun using the ABCORA test to investigate the cross-reactivity of coronaviruses. Previous infections of a person with well-known, harmless cold coronaviruses could have an influence on the immune response in a SARS-CoV-2 infection. The virologist and her team can now investigate whether the cross-reactivity of coronaviruses has a positive or negative effect using samples from a large Swiss biobank (see video).
Testing without nasal swab
Testing, testing, testing is the official recommendation of the health authorities in the second wave of the Covid-19 pandemic. However, both PCR and antigen tests require a nasopharyngeal swab, which is rather unpleasant and simply not feasible in younger children. Testing via saliva sample would be a welcome alternative for many, thought Trkola. “Especially for children or for adults who have to be tested frequently, saliva as a material for detection is a great advantage” – after all, young and old alike can spit. The Institute of Medical Virology has now conducted a large evaluation study to test whether SARS-CoV-2 can be detected in saliva by RT-PCR. “The evaluation has shown that it works very well,” says institute head Trkola.
The saliva tests should be available soon, once they have been approved by the Federal Office of Public Health. The saliva sample can be easily taken at home, stresses Trkola, as she explains how simple it would be for a young family, for example: “Parents have to get their child to spit into an empty, wide tube. Then, from a second tube, they pour a stabilizing liquid into the tube with the spit, close it with a cap and shake it so that it mixes well. They then put the tube inside a larger transport tube and send it by mail to a test center.” When children have colds, parents are often unsure what to do: The saliva test could quickly and easily put their minds at rest. “Schools and pediatricians would also be happy to have the option of such a test,” says Trkola.
Risk factors for developing serious illness
Onur Boyman, head of the Department of Immunology at the UniversityHospital Zurich (USZ) and professor of clinical immunology in the Faculty of Medicine at UZH, is investigating the reasons why some people get seriously ill with Covid-19. What he has observed at USZ to date confirms that active pre-existing conditions such as diabetes, certain heart and lung diseases, obesity and active cancer can have a negative impact on the disease’s progression. This is also one of the reasons why older people have a higher risk of getting severely ill, as these pre-existing conditions are more common in old age, Boyman says. In severe cases in younger people, however, a more complex picture emerges than originally assumed. But hospitals have quickly learned how to treat severe cases (see video).
Antibodies after mild symptoms
Onur Boyman and his team are also investigating the various immune responses that occur after SARS-CoV-2 infection. They have found that in people with mild cases of Covid-19, IgA and IgG antibodies are likely to be only temporarily detectable in the blood, but may continue to be found in tears, nasal secretions and saliva. Their findings were recently published in the Journal of Allergy and Clinical Immunology.
What protects against reinfection?
The researchers are currently examining the immune cells of the innate and acquired immune systems of sick people immediately after they have been infected with SARS-CoV-2 and again after six months. They have observed remarkably high levels of certain immune cells called monocytes in the blood of Covid-19 patients. Now the researchers want to find out which immune cells give protection against a second infection with SARS-CoV-2.
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