Humans tend to overestimate the danger of apparent low probability, high impact events (like pandemic ebola) and underestimate the risks involved in mundane events (like driving a car).
Given how infrequent pandemics occur, a better way to judge the risks involved would be to take a much long term view and try to measure the risk of a major pandemic occurring in your lifetime. When you look at the history of plagues over the last 2500 years they are infrequent, but common enough that we can get some handle on the risk. My very rough calculations based on past pandemic frequencies and death rates put the risk at around 1 in 1000 of being killed by a pandemic sometime during your lifetime. This is not huge, but at the same time it is not trivial.
Edit. I added the word apparent to the “…danger of…” as I realise that my wording is confusing without it.
I might have worded it better, but pandemics are actually one of those areas that people get the risks wrong for the opposite reason than usual. While pandemics are considered low frequency, high risk events and so over-worried about, they are actually relatively frequent events on a historical time scale and are not worried about as much as they should be. They are really more in the car crash category not the stuck by lightning category, but we get complacent because a big one has not happened in living memory (unless you count HIV).
Ah, yeah, that is a bit of a different angle on it. Truth be told, I'm not sure whether or not we're underrating the risk. On the one hand, increased travel and population density should see faster spread.
On the other hand we have a lot of changes in our favor: understanding how diseases are spread (starting with germ theory, all the way up through population models), understanding how many more diseases are treated, an astoundingly better ability to communicate, probably a better ability to coordinate...
I don't know how it nets out. The streak we've had should be taken as some evidence that it breaks in our favor. Certainly we should not succumb to the gambler's fallacy, there. However, I think we're well served to keep an eye on things.
Yes it is really difficult to know how the two major forces are tipping the likelihood. We have a better understanding of how contagious disease is spread and on average much better immune systems because of better diets (the average person was starving when most plagues struck in the past). Balancing this is as you mention increased travel and much high population densities. You just have to see the spread of a contagious disease through a modern animal feedlot to know what this does. All of this makes it really hard to know which way the risk has changed.
My biggest fear is a pandemic Rhadinovirus since it is airborne, has a long incubation phase and leukaemia is the outcome [1]. Something like a human pathogenic Ateline or Saimiriine herpesvirus could spread through the human population without us knowing until it is too late.
Interestingly, Saimiriine herpesvirus has recently been linked to idiopathic pulmonary fibrosis [2]. All it would take is a more pathogenic strain of this virus and we would be in a lot of problems.
Given how infrequent pandemics occur, a better way to judge the risks involved would be to take a much long term view and try to measure the risk of a major pandemic occurring in your lifetime. When you look at the history of plagues over the last 2500 years they are infrequent, but common enough that we can get some handle on the risk. My very rough calculations based on past pandemic frequencies and death rates put the risk at around 1 in 1000 of being killed by a pandemic sometime during your lifetime. This is not huge, but at the same time it is not trivial.
Edit. I added the word apparent to the “…danger of…” as I realise that my wording is confusing without it.