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There as been a lot of talk on whether spring will stop #SARSCoV2 #COVID19 (probably not). We (me, @robert_dyrdak Valentin D, @firefoxx66, @Jan_Albert_) used data on endemic CoVs to estimate seasonal forcing and its impact on a potential pandemic. [1/9] https://www.medrxiv.org/content/10.1101/2020.02.13.20022806v1
CoVs causing common cold show a pronounced seasonality in Sweden with about 10-fold higher fraction of positive tests in winter than in summer (similar to influenza and CoV data reported for other countries.) [2/9]
![CoVs causing common cold show a pronounced seasonality in Sweden with about 10-fold higher fraction of positive tests in winter than in summer (similar to influenza and CoV data reported for other countries.) [2/9]](https://pbs.twimg.com/media/ERAEUXqXsAEcV_s.png "CoVs causing common cold show a pronounced seasonality in Sweden with about 10-fold higher fraction of positive tests in winter than in summer (similar to influenza and CoV data reported for other countries.) [2/9]")
These data constrain the parameters of SIR models but different combinations of forcing and migration rates are compatible with the data. We believe a scenario with rapid exchange of viruses between regions and strong seasonal forcing is more plausible. [3/9]
![These data constrain the parameters of SIR models but different combinations of forcing and migration rates are compatible with the data. We believe a scenario with rapid exchange of viruses between regions and strong seasonal forcing is more plausible. [3/9]](https://pbs.twimg.com/media/ERAEU0_WkAA6to5.png "These data constrain the parameters of SIR models but different combinations of forcing and migration rates are compatible with the data. We believe a scenario with rapid exchange of viruses between regions and strong seasonal forcing is more plausible. [3/9]")
Using these (wide) parameter ranges, we can explore how introductions from Hubei would unfold in the temperate zones of the Northern Hemisphere. Depending on the value of R0 and peak transmissibility, an early peak, a peak in Winter 2020/21, or a double peak are plausible. [4/9]
![Using these (wide) parameter ranges, we can explore how introductions from Hubei would unfold in the temperate zones of the Northern Hemisphere. Depending on the value of R0 and peak transmissibility, an early peak, a peak in Winter 2020/21, or a double peak are plausible. [4/9]](https://pbs.twimg.com/media/ERAEVOQXkAE4NV8.jpg "Using these (wide) parameter ranges, we can explore how introductions from Hubei would unfold in the temperate zones of the Northern Hemisphere. Depending on the value of R0 and peak transmissibility, an early peak, a peak in Winter 2020/21, or a double peak are plausible. [4/9]")
Variation in R0 and peak transmissibility around the world could result in a superposition of fast and slow epidemics spreading prevalence through 2020 and 2021. A long drawn out pandemic such as this would reduce the burden on health care systems and supply chains. [5/9]
But seasonality is unlikely to stop #SARSCoV2 spread completely. The A/H1N1 pandemic in 2009 and previous influenza pandemics showed similar patterns with multiple waves hitting different parts of the world at different times. [6/9]
Eventually, a pandemic virus could settle into an endemic virus similar to the current seasonal CoVs or influenza viruses. [7/9]
![Eventually, a pandemic virus could settle into an endemic virus similar to the current seasonal CoVs or influenza viruses. [7/9]](https://pbs.twimg.com/media/ERAEV9_XUAAiWnz.jpg "Eventually, a pandemic virus could settle into an endemic virus similar to the current seasonal CoVs or influenza viruses. [7/9]")
Since the parameters underlying these models are uncertain and the models are a caricature of real-world complexity, this work is meant as an exploration of possibilities to help interpret changes in prevalence, not as a definitive prediction. [8/9]
We don't know whether #nCov #SARSCoV2 will cause a pandemic. But it can spread rapidly and has seeded small clusters in many places -- a pandemic is a possibility. Health care systems and supply chains need to prepare for this case as much as possible. [9/9]
