Epidemic modellers in Zurich predict a possible second wave of Covid-19 in Switzerland. Their forecast suggests it could be more deadly than the first if no effective treatments or vaccines materialise.
The modelling work, done by Fadoua Balabdaoui and Dirk Mohr at the Swiss Federal Institute of Technology in Zurich (ETHZ), predicts Switzerland’s state of “new normal” could lead to a second wave that results in a further 5,000 deaths. The second wave would start off more slowly than the first but last for longer – see chart d on page 10.
The model includes symptomatic (60%) and asymptomatic (40%) cases and compartmentalises the population based on age, something that allows it to account for age-related death risk and to model different age-based spread rates. It then forecasts outcomes based on infection and infection fatality rates (IFR) from Switzerland’s first wave combined with different reproduction rates scenarios. Symptomatic cases are assumed to be twice as infectious as asymptomatic cases.
Under a scenario with no relaxation of containment measures less than 10% of the population would be infected by the end of 2020 and an estimated 2,300 would die, with less than 0.4% of those aged 80 years and older losing their lives.
Under a scenario where the country shifts to a “new normal” the model predicts a second wave that peaks in mid-August 2020 with approximately the same daily peak hospital and ICU load as the first peak. Under this scenario 30% of the population is infected and there are an additional 5,000 fatalities.
This scenario is described as a “step-wise release of measures including school reopening without special caution”. For the purposes of modelling this scenario the differences between life before Covid-19 and “new-normal” are enforced social distancing (or at least mask wearing) at work and other locations and that 30% of the workforce continues to work from home.
Balabdaoui and Mohr also modelled the extreme and practically infeasible scenario of temporarily isolating all individuals older than 70 years from the rest of the society while letting life resume free of all restrictions for all other age groups. This scenario results in a 67% infection rate and an estimated 4,100 deaths. However, under this scenario, the peak hospital and ICU demand would likely exceed hospital capacity and cause additional fatalities, they said.
According to the authors, much depends on transmission rates and the rate of hospital admissions. The model is particularly sensitive to the transmission rate in schools and the percentage of workers returning to the office. If the reproduction number in schools goes below 1 then second peak deaths could be lower or even largely avoided. A reproduction number of 1 means an infected individual infects one other person.
In the end, the model suggests the scale of a second peak largely depends on how well Switzerland performs on social distancing, mask wearing and hand hygiene. If reproduction numbers rise too high in schools or work places the virus could gain the upper hand again.
Any model that attempts to model something as complex as the spread of a virus will produce uncertain results. Any results should be interpreted with caution.
Over the last week Switzerland recorded 117 new cases and 3 deaths.
On 3 June 2020, Dr Hans Kluge, WHO Regional Director for Europe, said while discussing the situation in Europe that a second wave is not inevitable – yet, as more and more countries relax restrictions there is a clear threat that Covid-19 infections may surge. If those surges are not properly managed, then a second wave could happen and could be extremely destructive. Remember, that we are no better off today than we were at the beginning of the year, we still do not have a vaccine nor treatment for COVID-19. Later he added, we must, all of us, be vigilant and behave responsibly, for all our sakes.
Iran, where the first cases were reported on 19 February 2020, has seen a resurgence in new daily cases. After reaching a low of 802 new cases on 2 May 2020, new daily cases have risen, reaching 3,134 on 3 June 2020, a number only slightly below first peak in daily cases of 3,186 on 30 March 2020.
Research paper (in English)