Superspreaders and numbers R and K

We are now entering a new phase of the coronavirus epidemic in which the numbers of newly infected people are small but there are still many susceptible individuals. The virus is, unfortunately, not going away, but the outbreaks will now change their character. Instead of a single large growing epidemic wave, we are likely to see smaller – but still substantial and potentially lethal – outbreaks.

Epidemiologists use models to understand the details of viral transmission, and they are now talking about a new number, K, in addition to the famous number R. I have written an explanation of why K is important for The Conversation, Is the K number the new R number? What you need to know. A more technical description is available on this blog, under the title of What is the number K?

By the way, the readership of my articles in The Conversation has now crossed the 500,000 number, including well over 300,000 readers for the second wave article. Thank you all for your support!

Face masks

When I was writing my first post on coronavirus back in March, I advised against wearing a mask. This was then consistent with the WHO position and seemed to have sense.

The WHO advice has changed quite recently and it seems that masks are now recommended in situations when social distancing is not possible. There is also evidence that they actually affect the transmission, largely by blocking the droplets on which virus can travel.

This means that there is no need to be very strict with the quality of the mask, so it does not necessarily need to block the virus from passing through. Hence, any face covering that blocks the droplets will do the job.

Testing and cases

I could not resist quoting from a tweet by a well-known person who will remain nameless here:

Our testing is so much bigger and more advanced than any other country (we have done a great job on this!) that it shows more cases. Without testing, or weak testing, we would be showing almost no cases. Testing is a double edged sword – Makes us look bad, but good to have!!!

Twitter, 15th June 2020

This is absolutely right! But with one caveat: These are reported cases, not real cases. Of course, if there is no testing and no reporting, there will be no reported cases but of course, there will still be infections and deaths going on in the background.

What does matter, is less the actual numbers, but the trend. I wish journalists would stop at saying ‘the largest/second largest death numbers‘ but concentrate on the increase/decrease (or at least on relative numbers, for example per head).

The trend is actually not good in the country this tweet comes from (R is still close to 1), which makes testing even more important.

Why is testing important? Why do we need to know how many infected individuals are there? Mainly to see whether our strategy of confining the virus works or not and what are the risks associated with changing the strategies. More on it in my article on the second wave at The Conversation. We also need it to guard against superspreading events, as described here, so my advice is that any large gatherings like planned here should be accompanied by big and advanced testing.

So, I fully agree with the author – testing is good to have!