Importation Risk Index calculation
The specific methodology to derive importation risk index for a for a given destination was demonstrated by many researchers (Haider et al., 2020; Massad & Wilder‐Smith, 2009). Based on these studies we used the similar methodology to derive the importation risk index using the following equation.
\(Importation\ risk\ index=\sum_{i=1}^{n}{a\frac{P}{T}\frac{I}{N}}\)
where, a is the transmission rate, which is assumed to be 2.5 (recommended by WHO), P is the total number of India bound seats from the international airports in the origin country, and T is the total number of seats in all the airlines originating from the selected airports or origin country. I is the total number of 2019-nCoV infected patient in the origin country and N is the population of the origin country. The Importation Risk Index is a weighted risk number and is proportional to the risk possessed by a country to import 2019-nCoV cases into India.
The estimation was carried out for 24 airports selected across ten countries, and a Pearson Correlation coefficient test between the estimated risk index and the total number of imported 2019-nCoV cases in India from these countries up to 24th March, as reported by the government, was performed. The detailed results are presented below.