linikujp
commented
4 years ago @PhiBabs935 : My understanding is the holoendemicity is focused on infection, but not manifestations of the disease. Hyperendemicity is about the disease manifestation that has a high prevalence rate.
My feeling of using frequency of symptoms between young and old is too limited to diseases itself. Given the example of COVID-19. The frequency of symptoms is higher in old than young. Better not define it in such a level of details, I think.
I will reach out to Dr. Salwa who is an epidemiologist and helped with IDOBRU for this question. I think if you will need a call, we can add her to the call.
For reference: https://www.ncbi.nlm.nih.gov/mesh?term=Endemic+Diseases
PhiBabs935
In the IDO paper, we agreed to add some subclasses of infectious disease endemicity (terms that appeared in IDOMAL previously). But I am having some trouble pinning down how these terms should be defined. Below is some brainstorming./musing Indeed, I think discussion of these terms, as well as the other infectious disease epidemiology quality terms currently present in IDO, might warrant a planned call at some point in the future (perhaps we should even try to see if anyone knows an ontologist that is a domain expert in epidemiology who could weigh in).
Infectious disease endemicity =def A quality that inheres in an organism population in virtue of the fact that infections of the type that causes an infectious disease are maintained in the population via intra-population via intra-population transmission or by transmission from a local reservoir.
We should add the following subclasses: infectious disease holoendemicity, infectious disease hyperendemicity, infectious disease mesoendemicity, and infectious disease hypoendemicity.
Now, essentially these are terms used to classify the varying degrees to which a disease can be endemic to a given population. From what I read, for some infectious diseases, such as malaria, degrees of endemicity are well-defined in terms of percentages. But this is not the case for all infectious diseases.
"Levels of endemicity can be classified as holoendemic, hyperendemic, mesoendemic, hypoendemic depending upon whether a disease occurs with, respectively, extreme, high, moderate, or low frequency." (https://www.sciencedirect.com/topics/medicine-and-dentistry/holoendemic)
Clearly, levels of endemicity has to do with the frequency of something, but from the literature it is not clear to me what exactly that something is supposed to be. The above says "disease occurrences". I raise this issue because when I first started thinking about coming up with definitions for these terms, I looked at how other related infectious disease epidemiology quality terms were defined in IDO.
For instance, Infectious disease sporadicity =def A quality that inheres in an organism population by virtue of the fact that realizations of an infectious disease occur in the population with a fluctuating prevalence.
So my first thought was that perhaps the subclasses of endemicity could be defined similarly, assuming that we read "frequency of disease occurrence" as "frequency of disease realizations". On this reading, we might define infectious disease holoendemicity as something along the lines of: "An infectious disease endemicity that inheres in an organism population by virtue of the fact that realizations of an infectious disease occur in the population with an extreme frequency." [And similarly for the other three subclasses of endemicity]
But I am not so sure...
For instance, take holoendemicity. This term is used for diseases in which virtually everyone in the population is infected with the pathogen responsible for causing the disease. But, crucially, in the case of holoendemicity, it is typical that younger members of the population are more likely to express pathogenic responses and show symptoms of the disease, whereas older members of the population are more likely to be asymptomatic, or experience reduced damage from the disease, due to adaptive immunity (immunity which has arisen because of the extremely intense frequency of infection within the population).
This suggested to me that it might be very misleading to characterize holoendemicity in terms of frequency of disease realizations--indeed it seems that in the case of holoendemicity the opposite is the case: disease realizations (symptoms, pathogenic bodily processes) only occur with an extreme frequency in the younger members of the population, not the older members.
Consider by contrast hyperendemicity, which is usually characterized as a persistently high frequency of disease occurrences. In the case of hyperendemicity, symptoms of the disease are expressed equally by members across all age groups.
Another worry, and here I have to do more research [this may just be indicative of my ignorance on the details of the science]: when discussions of levels of endemicity come up, is there perhaps a conflation of infection occurrence and disease occurrence? In the case of holoendemicity, do all of the asymptomatic adult hosts who are infected with the relevant pathogen actually have the disease itself in the strict sense of the term?
Now, while many sources I read classify the subclasses of endemicity in terms of frequency of disease occurrence, this is not ubiquitous. For instance some sources characterize them in terms of intensity of transmission. For instance, here (http://chsrd.aua.am/malaria/eng/epidemiology.php): with regard to malaria endemicity, holoendemicity is characterized as "intense transmission resulting in a considerable degree of immunity outside early childhood"; hyperendemicity as "Areas where transmission is intense but seasonal; immunity is insufficient in all age groups"; mesoendemicity as "Typically found among rural communities in subtropical zones where wide geographical variations in transmission risk exist"; and hypoendemicity as "Areas where there is a little transmission and the effects, during the average year, upon the general population are unimportant"
Similarly, the definitions of the relevant terms, as they appeared in IDOMAL, focus on transmission. For instance, IDOMAL:holoendemicity =def Holoendemicity denotes a perennial transmission of high degree, resulting in a considerable degree of immune response to all age groups, but particularly in the adults
Now, depending on how strict you are about the term transmission, this seems to suggest that attributions of levels of endemicity are really about frequency of transmission of pathogens, and subsequent infections, and not necessarily the prevalence of instances of the disease per se.
Thus, I thought that alternatively, we could define the relevant subclasses in a way that focuses on either frequency of the presence of infections (material entity), frequency of the occurrence of infections (process), or frequency of the occurrence of transmission of the pathogen--the latter of which is continuous with the definition of "infectious disease endemicity" and its focus on transmission.
For instance, something along the lines of:
Holoendemicity = An infectious disease endemicity that inheres in an organism population by virtue of the fact that infections of the type that causes an infectious disease are present in most members of the population. Or "An infectious disease endemicity that inheres in an organism population by virtue of the fact that infections [processes of establishing an infection] of the type that causes an infectious disease occur in the population with an extreme frequency." Or: "An infectious disease endemicity that inheres in an organism population by virtue of the fact that transmissions occur in the population with an extreme frequency"
And similarly with the other subclasses of endemicity...
If one went this route, the points about the frequency of symptoms between young and old members of the population could be added as a comment for holoendemicity? Likewise with the other subclasses of endemicity.