Table 4.

Risk Factors for Severe Acute Respiratory Syndrome Coronavirus 2 Transmission in the Household

Index or Household Risk Factor	Susceptible Household Contacts	Incident Secondary Cases	Secondary Household Attack Rate (95% CI)	Odds Ratio (95% CI)	Adjusted Odds Ratio (95% CI)
Non-White	41	21	51% (33–69)	4.4 (1.5–13.0)	4.8 (1.5–15.4)
White, non-Hispanic	62	12	19% (10–35)	-
Higher index nasopharyngeal viral loada	-	-	-	3.5 (1.5–8.1)	3.6 (1.5–8.5)
High living densityb	29	15	52% (27–75)	3.3 (1.02–10.9)	1.4 (.4–4.6)
Not high living density	74	18	24% (15–37)	-

Adjusted odds ratio adjusts for viral load as a continuous variable and race-ethnicity and living density as dichotomous variables.

Abbreviation: CI, confidence interval.

^aOdds ratio for 3 log₁₀ increase in the index viral load (VL). For example, the odds of transmission in a household where the index VL is 1 × 10⁹ copies/mL is 3.5 times greater than in a household where the index VL is 1 × 10⁶ copies/mL.

^bDefined as more than 3 people occupying fewer than 6 rooms.