Table 3. Relationship between DENV lineage extinction and polarization in fitness in populations.

DENV fitness polarization	Lineage		Total
	Extinct	Circulating
Polarized	3	1	4
Non-polarized	1	4	5
Total	4	5	9

75% of the extinct viral strains were polarized and 80% of the circulating strains were non-polarized. We have conducted a Chi-square test of independence to test the null hypothesis that there is no association between polarization and virus extinction. The test results show that there is no statistically significant association between polarization and virus extinction (Pearson Chi- square statistic = 2.7, p = 0.09).