Smallpox epidemiology and demographics: Difference between revisions
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[[Image:Smallpox-1.png|left|400px|thumb|Incidence of reported cases in the 31 countries and territories in which smallpox was endemic in 1967.]]<br clear="left"/> | [[Image:Smallpox-1.png|left|400px|thumb|Incidence of reported cases in the 31 countries and territories in which smallpox was endemic in 1967.]]<br clear="left"/> | ||
In [[endemic]] regions there were periods called ''epidemic years'' in which the [[incidence]] was much higher. In order to try to justify this discrepancy, several possibilities were evoked, such as: | In [[endemic]] regions there were periods called ''epidemic years'' in which the [[incidence]] was much higher. In order to try to justify this discrepancy, several possibilities were evoked, such as:<ref name=WHO>{{cite web|title=The epidemiology of smallpox|url = http://whqlibdoc.who.int/smallpox/9241561106_chp4.pdf}}</ref> | ||
* Viability of the [[virus]] | * Viability of the [[virus]] | ||
* Changes in susceptibility of the host | * Changes in susceptibility of the host | ||
* Social factors, such as dispersion of the population | * Social factors, such as dispersion of the population | ||
* | * Seasonal variation in [[incidence]] in relation to eradication | ||
==Age== | ==Age== |
Revision as of 18:17, 13 July 2014
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Overview
The true incidence of smallpox, before declared eradicated in 1980 by the WHO, wasn't possible to specify due to the lack of new case reports from countries, particularly endemic regions, in which the reported numbers are stipulated to be 1-2% of the reality. Children and young adults were the most affected, especially in regions with low level of immunity. There is no evidence of gender or race difference in the incidence of the disease. Developing countries had a higher incidence of the disease.[1]
Incidence
The number of new cases, reported to the international health authorities, varied greatly in accuracy. The data obtained from non-endemic countries, with good health services, was probably the most accurate. Yet, according to the Intensified Smallpox Eradication Programme, the reported incidence amounted only to 1-2% of the reality, which made it impossible to obtain a true number on the incidence.[1]
In endemic regions there were periods called epidemic years in which the incidence was much higher. In order to try to justify this discrepancy, several possibilities were evoked, such as:[1]
- Viability of the virus
- Changes in susceptibility of the host
- Social factors, such as dispersion of the population
- Seasonal variation in incidence in relation to eradication
Age
The age incidence of the disease depended on the level of acquired immunity of the population. When populations were exposed to the disease for the first time, all ages would be infected. In endemic regions, where there was some previous level of immunity, children and young adults were the most affected.[2][1]
Gender
Smallpox affected males and females equally.[1]
Race
Despite potential racial susceptibility, differences in incidence of the disease according to the race were never demonstrated.[1]
Developed Countries
Developed countries, due to a better established health system had lower incidence of smallpox and better reports of the new cases to the international organizations.[1]
Developing Countries
In some countries, particularly in developing countries, healthcare facilities were distrusted by the populations, hence some cases were hidden from public health authorities. Also, some religious beliefs were agains vaccination. Some of these factors might explain the higher incidence of smallpox in these countries.[1]