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A Bit More About Historical Pandemics
Feb. 6th, 2020 08:59 amMany, many, many things affect the spread of disease.
When thinking about flu-like illnesses, such as the flu, or coronavirus, or other respiratory diseases, we know some things strongly influence their severity, and yet somehow manage to rarely talk about them.
Obviously, the flu vaccine has reduced the severity of outbreaks (some more than others). Less appreciated, the measles vaccine has almost certainly reduced the severity of every flu outbreak since sometime around the mid 1960s. When people get measles, there is a negative effect on their immune system memory -- recently we have been able to more directly measure this effect. It is significant, even when the measles case was not particularly severe, but more serious measles cases lose even more immune system memory. In a world of persistent epidemic measles, no one could rely on persistent immunity from anything. In a world in which measles was eradicated, (almost) everyone can rely on persistent immunity from a lot of things. Especially things like the flu.
I have already mentioned that Reye's syndrome was not really recognized until the 1960s, and that the risk to young adults as well as children is still only now being fully comprehended. But the fever reducer turned to after aspirin would have been tylenol / acetaminophen / paracetamol. Which I probably spelled wrong. We are still trying to grasp how alcohol and acetaminophen interact. We know it is worse with some people than with others. What is clear is that Reye's and tylenol + alcohol produce liver damage in some people, that can look like flu symptoms. While one might wonder how this could affect mortality and morbidity in flu outbreaks, it is not unheard of even now to use alcohol based cough medicines (including spirits) in children (or by young adults). It is easy to imagine that a combination of efforts to make febrile children or young adults more comfortable and reduce their symptoms might have found people more at risk from liver damage. Specifically, tonsillectomy was super common in this same time frame (post-WW2 but before 1970), and a lot of people received blood transfusions as part of the procedure or afterwards due to hemmorhage. The blood supply was not at that time monitored for much of anything, and is believed now to have had quite high rates of various forms of hepatitis within it. Still more potential for liver failure (which looks like the flu in some cases). And hepatitis itself can look like the flu.
I would summarize the above two risks as: immune amnesia subsequent to measles increasing mortality and morbidity for each outbreak of flu in people who otherwise would have had some degree of immunity, and multiple kinds of liver damage with potentially multiple causes masquerading as flu.
The third thing we do not talk about much when we talk about respiratory illnesses is pre-existing lung damage making some people a lot more vulnerable to the illness. The longer a person lives, the more potential they have to encounter something that damages their lungs (including previous bouts of respiratory illness) -- an older population, all other things being equal, is more likely to have lung damage. The median age in China is quite close to the median age in the United States (US is every so slightly older)[ETA: US age structure is flatter, and has more people in the very oldest chunks. China has large chunks in age ranges that can be kind of vulnerable. I wonder if this has a meaningful effect.]. Two other factors, however, have rendered the United States increasingly less susceptible to respiratory illnesses: reduction in smoking throughout the population, and an improvement in air quality throughout the country. It is worth noting that in both of these areas, China is significantly lagging the United States. [ETA: But rates of women smoking remain quite low in China vs. the US.] I expect that their hierarchical structure will deploy their improvement in best practices to notice this effect, and work very hard in the decade to come to discourage smoking, and perhaps to use medical science to convince the government as a whole to work on improving air quality (something the Chinese people as a whole would like very much).
In conclusion, if we look at a respiratory outbreak in China, and attempt to anticipate what that outbreak would look like in the United States, there are some factors (notably smoking rates, and lifetime air pollution exposure) that will make that comparison scarier than it maybe should be. If we look at an outbreak from our own past, and anticipate what a similar infecting agent might do in the future, there are other factors that will make that comparison scarier than it maybe should be.
When thinking about flu-like illnesses, such as the flu, or coronavirus, or other respiratory diseases, we know some things strongly influence their severity, and yet somehow manage to rarely talk about them.
Obviously, the flu vaccine has reduced the severity of outbreaks (some more than others). Less appreciated, the measles vaccine has almost certainly reduced the severity of every flu outbreak since sometime around the mid 1960s. When people get measles, there is a negative effect on their immune system memory -- recently we have been able to more directly measure this effect. It is significant, even when the measles case was not particularly severe, but more serious measles cases lose even more immune system memory. In a world of persistent epidemic measles, no one could rely on persistent immunity from anything. In a world in which measles was eradicated, (almost) everyone can rely on persistent immunity from a lot of things. Especially things like the flu.
I have already mentioned that Reye's syndrome was not really recognized until the 1960s, and that the risk to young adults as well as children is still only now being fully comprehended. But the fever reducer turned to after aspirin would have been tylenol / acetaminophen / paracetamol. Which I probably spelled wrong. We are still trying to grasp how alcohol and acetaminophen interact. We know it is worse with some people than with others. What is clear is that Reye's and tylenol + alcohol produce liver damage in some people, that can look like flu symptoms. While one might wonder how this could affect mortality and morbidity in flu outbreaks, it is not unheard of even now to use alcohol based cough medicines (including spirits) in children (or by young adults). It is easy to imagine that a combination of efforts to make febrile children or young adults more comfortable and reduce their symptoms might have found people more at risk from liver damage. Specifically, tonsillectomy was super common in this same time frame (post-WW2 but before 1970), and a lot of people received blood transfusions as part of the procedure or afterwards due to hemmorhage. The blood supply was not at that time monitored for much of anything, and is believed now to have had quite high rates of various forms of hepatitis within it. Still more potential for liver failure (which looks like the flu in some cases). And hepatitis itself can look like the flu.
I would summarize the above two risks as: immune amnesia subsequent to measles increasing mortality and morbidity for each outbreak of flu in people who otherwise would have had some degree of immunity, and multiple kinds of liver damage with potentially multiple causes masquerading as flu.
The third thing we do not talk about much when we talk about respiratory illnesses is pre-existing lung damage making some people a lot more vulnerable to the illness. The longer a person lives, the more potential they have to encounter something that damages their lungs (including previous bouts of respiratory illness) -- an older population, all other things being equal, is more likely to have lung damage. The median age in China is quite close to the median age in the United States (US is every so slightly older)[ETA: US age structure is flatter, and has more people in the very oldest chunks. China has large chunks in age ranges that can be kind of vulnerable. I wonder if this has a meaningful effect.]. Two other factors, however, have rendered the United States increasingly less susceptible to respiratory illnesses: reduction in smoking throughout the population, and an improvement in air quality throughout the country. It is worth noting that in both of these areas, China is significantly lagging the United States. [ETA: But rates of women smoking remain quite low in China vs. the US.] I expect that their hierarchical structure will deploy their improvement in best practices to notice this effect, and work very hard in the decade to come to discourage smoking, and perhaps to use medical science to convince the government as a whole to work on improving air quality (something the Chinese people as a whole would like very much).
In conclusion, if we look at a respiratory outbreak in China, and attempt to anticipate what that outbreak would look like in the United States, there are some factors (notably smoking rates, and lifetime air pollution exposure) that will make that comparison scarier than it maybe should be. If we look at an outbreak from our own past, and anticipate what a similar infecting agent might do in the future, there are other factors that will make that comparison scarier than it maybe should be.