Quam and Wilder-Smith reported the importation index for evaluating sources of spread of dengue fever by air travelers. The same tool can be used for other infections as well. The authors are from Umea University in Sweden and Nanyang Technological University in Singapore.
Parameters:
(1) incidence of dengue in a specific country over a given period of time
(2) number of air travelers from a country to that specific country over the same period of time
importation index related to travelers from a country =
= (incidence rate) * (number of air travelers)
where:
• The time interval can be year or month.
• Incidence is usually a population rate but the denominator may vary.
• Not all air travelers will share the same risk.
Interpretation:
• Countries with the highest importation index are more likely to be countries of origin for imported cases of dengue fever.
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