“People are most at risk in poorly ventilated rooms”

Dr Sigel, we are currently experiencing another wave of Covid, but no one seems to be particularly worried by it. Is that your impression as well?
It¡¯s certainly the impression you might get in the public domain, because so few people still wear face masks. Life seems to be getting back to normal. After two and a half years of pandemic, people really are desperate for a return to normality, which is equally important for mental health too. But as you say, the number of reported cases is starting to rise again. The reason the cantons have not yet taken action has to do with certain characteristics of the current Covid surge. But that does not mean no one is worried. A raft of data is being closely tracked to ensure a rapid response is possible if necessary. Monitoring wastewater, for example, allows us to assess the scale of rising infection rates, while genome sequencing provides qualitative information on new Covid variants, and hospital bed capacity is constantly monitored. Apart from that, the Medical Association has already called for wider use of face masks again in clinical environments.

You mentioned the characteristics of the current wave ¨C What precisely do you mean?
We have recently discovered that the current subvariants of omicron that are driving this summer Covid surge are more infectious than previous variants. So far, however, there has been no evidence of patients becoming seriously ill. The number of patients hospitalised with Covid-19 has risen, but not the occupancy of intensive care units. Higher infection rates are unlikely to overwhelm the Swiss healthcare system. Even so, we need to stay more alert over the coming months so that we can take any necessary preventive measures in good time. Thanks to national vaccination programmes and immunity from previous infection, Switzerland¡¯s population has a high level of resistance to SARS-CoV-2. Because our immune system uses different defence mechanisms, protection against severe progression of the disease persists, even if resistance to infection can diminish over time.

But an infection could still leave someone with Long Covid¡­
Based on current knowledge, five to ten percent of infected patients may go on to develop post-Covid-19 symptoms, but in most cases these usually disappear again after several months. Unfortunately, the symptoms may turn into a long-term chronic condition in individual cases. These people need support ¨C both medically and socially.

How high is the risk of infection in Zurich, or indeed across Switzerland as a whole?
That¡¯s very hard to say, because many people who are infected do not get officially tested. The high percentage of positive test results would seem to suggest a high number of unreported cases. One thing is certain, however: the weekly index is high at present. The biggest risk is in poorly ventilated rooms, such as restaurants and bars where people are engaged in lively conversation over long periods. Public transport can also be risky, depending on how crowded it is.

So how should we behave?
Wearing a mask is recommended in indoor spaces with poor ventilation and generally where there are large gatherings of people. As for ETH, the situation in lecture halls gives us most concern. Various experiments and simulations show that our lecture halls are well ventilated, but that still does not mean students shouldn¡¯t wear a face mask. When lecture halls are full, we continue to recommend face masks, even though we are well aware that everyone is tired of wearing them. There are no lectures at present, so our recommendation is not so relevant, except perhaps in situations such as large conferences¡­

The exam session starts on 8 August: how should students behave?
In most exam sessions, there¡¯s adequate distancing between students and no talking is allowed. Anyone who wants to reduce their risk of infection should wear a face mask. But the most important message is still: if you have any symptoms, stay at home ¨C don¡¯t come to the university. If necessary, the Rectorate will communicate any changes to the recommendations, or other requirements, before the exam session starts.

How can people minimise the risk of getting infected before sitting an exam?
The best way to minimise risk is to avoid any indoor gatherings two weeks before the exam. But obviously I am aware how restrictive this can be for young people.

With infection rates so high, it¡¯s still possible to get Covid even when taking precautions. What rules apply to ETH staff?
Anyone with symptoms must stay at home for at least five days and should only return to ETH having been symptom-free for two days. Anyone testing positive for Covid does not require a doctor¡¯s certificate as long as they are not absent for more than five days and their line manager has not previously demanded a certificate. This rule is meant to take pressure off GP surgeries. We therefore continue to urge all ETH employees to take a test if they have any symptoms. These tests are still free of charge.