What is this?
A graph of the positive tests for RSV and hMPV from 2014 through 2024.
What are RSV and hMPV?
RSV stands for respiratory syncytial virus
hMPV stands for human metapneumovirus
What is the frequency of the RSV season?
12 months
What defines when the seasons begin and end?
The season is defined as the time frame when the percent of positive test results is > 3%
This is not explicitly stated; however, it can be inferred from the blue areas representing the overlap of the two seasons. There are times when both viruses are present but there is no area colored blue (such as in 2024) because the percents have not reached the 3% threshold.
What is the duration of the RSV season?
About 5 months.
It looks like RSV season starts around November and ends around March.
What is the amplitude of the RSV season?
The percentage of test swabs that are positive for RSV peaks around 15% each year.
Which is more common?
In general, RSV is more common than hMPV, although at certain times of the year, hMPV becomes more common.
What does the break in the y-axis represent?
The break indicates there is a jump in the scale up to 100%. It is unclear that this is necessary. The upper tick mark could have been labeled 20% and the discontinuity could then have been left out.
Why does the break in the y-axis cause a problem for this graph?
It makes it hard to interpret the RSV peak in December of 2022. Presumably, the scale is really linear and that the peak is around 18%. But because it extends into the discontinuity, it is actually ambiguous.
I would not want to rely on this graph if there were the possibility of intentional deception, such as in a legal contract.
What happened to RSV and hMPV during the Covid-19 pandemic?
Cases of RSV and hMPV dropped off dramatically in the early part of the Covid-19 pandemic, presumably due to social isolation preventing the spread of the virus. However, the viruses then came back earlier (RSV peaked around September instead of January) and stronger (the area under both RSV and hMPV peaks in 2022 is larger than usual, indicating more total cases.)
What can be said about the relationship between RSV and hMPV?
The two viruses are correlated. hMPV always follows RSV. One might be tempted to interpret this as suggesting that hMPV is caused by RSV. However, this would be inferring too much from the graph.
It is easy to conceive of a graph that might look similar to this in which one curve is caused by the other. For instance, the graph of deaths from Covid would always peak a couple of weeks after the peak of positive Covid swabs.
However, in this case, the correlation between the two viruses are likely due to an underlying connection (the time of year). It might be argued that hMPV occurred earlier in the winter of 2021-22 than in previous years because RSV was earlier, and this shows that hMPV is caused by RSV rather than the time of year. However, the relationship between RSV and hMPV is again due to an underlying connection (this time, the distortion caused by the Covid pandemic). In fact, the seasons in 2023 and 2024 are less correlated, suggesting that hMPV is not caused by RSV.
What represents the total number of cases of RSV during a season?
The area under the curve from the point where the curve rises above the 3% line to the point where the curve descends below the 3% line. This includes the region extending down to the x-axis.
Goals of this image:
- Interpret graphs
- Understand errors in graphs
- Recognize the difference between causation and correlation
CoMo Science 
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