Table 1. Phylogeny-trait association tests of phylogeographic structure of DENV-2 in southern Viet Nam.

Statistic	Spatial clustering	Index Ratio, observed to expected (95% CI)	Observed value (95% CI)	Expected value (95% CI)	P-value
Association Index (AI)
Asian I	10 Provinces	0.60 (0.48–0.75)	5.3 (4.8–5.8)	8.9 (7.7–10)	<0.01
	9 Provinces, 3 HCMC	0.68 (0.59–0.81)	7.8 (7.4–8.3)	11.4 (10.3–12.5)	<0.01
	9 Provinces, 11 HCMC District Groups	0.69 (0.62–0.77)	9 (8.5–9.5)	13.1 (12.4–13.8)	<0.01
American/Asian	6 Provinces	0.82 (0.54–1.54)	1.4 (1.2–1.7)	1.7 (1.1–2.2)	0.18
	5 Provinces, 3 HCMC	0.92 (0.67–1.50)	2.3 (2–2.7)	2.5 (1.8–3)	0.31
	5 Provinces, 9 HCMC District Groups	0.84 (0.66–1.13)	3.1 (2.7–3.5)	3.7 (3.1–4.1)	0.06
Parsimony Score (PS)
Asian I	10 Provinces	0.75 (0.72–0.80)	40 (40-40)	53.2 (50–55.8)	<0.01
	9 Provinces, 3 HCMC	0.84 (0.80–0.89)	64 (64-64)	76.3 (72.1–79.7)	<0.01
	9 Provinces, 11 HCMC District Groups	0.92 (0.89–0.97)	85.6 (85–87)	92.8 (89.6–95.9)	<0.01
American/Asian	6 Provinces	1.01 (0.90–1.00)	10 (10-10)	9.9 (9–10)	1
	5 Provinces, 3 HCMC	1.01 (0.94–1.00)	16 (16-16)	15.8 (15–16)	1
	5 Provinces, 9 HCMC District Groups	0.98 (0.91–1.09)	27.3 (27–28)	27.8 (25.8–29.7)	0.27
Maximum clade (MC) scores *
Asian I	Dong Thap (DT)	NA	4 (4-4)	2 (1-3)	<0.01
	Tay Ninh (TN)	NA	2 (2-2)	1 (1-1)	<0.02
	Vung Tau (VT)	NA	2 (2-2)	1 (1-1)	<0.02
American/Asian	Ho Chi Minh City (HCMC)	NA	11.9 (11–16)	5.5 (3.2–9)	<0.03

*Only significant MC scores are indicated; for all other locations, p>0.05 as estimated using BaTS [31].