Coronavirus: Patterns

Here is a histogram of the daily new coronavirus cases in Sweden:

Note the peaks indicated by the vertical marks. Also note the regularity. Here is a similar plot from Germany:

And Italy:

And from Michigan, although in this case the plot is of new cases by date of onset:

Each of these demonstrates a regular exacerbation/remission pattern in the reporting of new cases. There are two possibilities associated with this observation: Either it reflects an underlying phenomenon or it does not. It is certainly possible that what is illustrated above is a coincidence, or perhaps some quirk in the way tests are collected, run and reported. The apparent pattern may simply be apophenia, the perception of patterns where there are none, or it may be a pattern reflecting something other than the way the virus infects people. 

The other possibility is that the patterns above reflect a characteristic of viral spread in populations. It appears as though there is an oscillation in new cases superimposed on the underlying bell-shaped curve. If this is the case, what might account for it? As proposed previously, this may reflect the possibility that the spread of the virus is more complex than simply the accident of a person encountering an inoculum of virions and becoming infected, and then passing it on to others. The dynamics of virus spread seem to involve other, not yet explained factors. Even though there is no plausible feedback mechanism currently being considered to understand how the contagion grows, peaks and recedes, inspection of the charts above indicates that, in certain cases at least, the virus behaves as though such mechanisms are present.