Mono in Mexico: An Epidemiological Study

An interesting primary article I found that is pertinent to my discussion of mononucleosis is "Clinical and laboratory characteristics of infectious mononucleosis by Epstein-Barr virus in Mexican children" by N. Saldana, V. Colin, G. Ruiz, and H. Olguin. You can check out the article in its entirety at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3413594/. It is a descriptive cohort epidemiological study that analyzes the prevalence of mono in Mexican children because little research has been done on the clinical symptoms of mono in developing countries such as Mexico. A cohort study was performed on 163 cases of mononucleosis in Mexican children ranging from ages 0 to 18 years old at the National Institute of Pediatrics in Mexico. The study began in 1970 and ended in 2011, with the accumulation of cases happening during this time period. Their ages, most prevalent symptoms, sex, and any complications were recorded.

Figure 1. Age of 163 patients included in the study grouped by age-ranges: A:0-2.5years (y), B:2.5-5 y, C:5-7.5 y, D:7.5-10 y, E:10-12.5 y, F:12.5-15 y, G:15-17.5 y.

As you can see from the above figure from the study, the age group with the highest prevalence of mononucleosis cases is younger than that of those in the United States. In the US, it is usually those who are teenagers that have the highest amount of mono cases at any given point. However, in this study, it shows that children in Mexico that are 0-7 years of age have the highest amount of cases of mono. So it seems that incidence is higher in developing countries such as Mexico at a younger age than in developed countries for mononucleosis. 

Figure 2 above shows how many cases has each of the respective symptoms. Generally, mononucleosis is characterized by fever, pharyngitis, and swollen lymph nodes, which are all most prevalent as seen in the graph. However, these symptoms occurred at different proportions than that of those in the United States. There were many statistics found on each, but I will summarize their most important findings that were contrary to findings in the United States. In the discussion, it explains how fever was more prevalent in Mexico than in the US, with about 70% of the cases getting it compared to 35% in the US. However, pharyngitis was seen in only about 55% of patients in Mexico, while in the US study it was seen in 100%. Irregular lymph nodes as well as swollen spleens were seen in similar numbers in both US and Mexican populations, and the rest of the symptoms were too few to properly compare. For the most part, they conclude that Mononucleosis was prevalent at earlier ages in Mexico than in industrialized countries, as well as the proportionality that different symptoms of the illness show up in the population.

Their research could definitely be followed up with some etiological studies, as well as clinical studies to see exactly why Mexican children are affected at a much younger age than that of those in developed countries. A study could be done to see how the disease is transmitted most commonly, and if this method of transmission is different than that of industrialized countries. It could be possible that another source is responsible for the spread of the disease other than personal contact. Are there other factors that lead to Mexican children getting this disease at a younger age? Maybe they are exposed to other things that older children are not. Just thinking out loud here, but maybe mononucleosis can be passed through another medium such as breast milk, so younger children are susceptible to it from their mother? Other studies asking why the proportions of different symptoms are so different between countries can be done to test for confounding factors. There may be other explanations for why kids in Mexico get more fever and less pharyngitis than their US counterparts. There could possibly be associations between the prevalence of certain symptoms and the age of the child, another important future direction of study. For the future, I think all of these directions would be beneficial in exploring mononucleosis in Mexico so that we may see differences between the disease in different countries.