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Epidemiology of infectious disease: the example of measles
Abstract:
The situation of unacculturated Brazilian Amazon tribes is described. The isolation of these populations has been sufficiently tight that they have been free of most epidemic diseases of the cosmopolitan world, although diseases associated with persistent infection have a high prevalence. The history of measles epidemics in Amerind populations is reviewed and it is concluded that most deaths can be prevented by basic nursing care but that there is a residual excess mortality characteristic of these populations. Three Brazilian virgin-soil populations and one experienced tribe in Chile, the Mapuche, were vaccinated against measles. Elevated febrile responses were observed in the three virgin-soil populations relative to the fevers seen in the Mapuche and in cosmopolitan populations. Nutritional status, immunological experience, humoral immune response and genetic characters have been examined for an explanation of this phenomenon. The most pronounced correspondence detected so far is a high degree of homozygosity in HLA loci of the virgin populations.
Insights
Unacculturated Amazonian tribes experienced severe measles (a viral disease) outbreaks. High HLA homozygosity in these populations may explain their heightened febrile responses post-vaccination, suggesting genetic factors influence disease severity.
Area of Science:
- Immunology
- Anthropology
- Genetics
Background:
- Unacculturated Brazilian Amazon tribes face unique health challenges due to isolation.
- These populations are vulnerable to epidemic diseases like measles, despite high prevalence of persistent infections.
- Historical measles epidemics in indigenous populations resulted in significant mortality, even with basic care.
Purpose of the Study:
- To describe the health status of unacculturated Brazilian Amazon tribes.
- To investigate the reasons for elevated febrile responses to measles vaccination in isolated populations.
- To explore the correlation between genetic factors, immune response, and disease severity.
Main Methods:
- Review of historical measles epidemics in indigenous communities.
- Measles vaccination of three virgin-soil populations in Brazil and one experienced tribe (Mapuche) in Chile.
- Analysis of nutritional status, immune experience, humoral immune response, and genetic markers (HLA loci).
Main Results:
- Virgin-soil populations exhibited elevated febrile responses to measles vaccination compared to the Mapuche and cosmopolitan populations.
- A high degree of homozygosity in HLA loci was observed in the virgin populations.
- Residual excess mortality was noted in these populations following measles exposure.
Conclusions:
- Genetic factors, specifically high HLA homozygosity, may contribute to the exaggerated febrile response and disease severity in unacculturated populations.
- While basic nursing care mitigates some mortality, unique population characteristics influence measles outcomes.
- Further research into immunological and genetic factors is warranted to understand disease susceptibility in isolated indigenous groups.