Table 3. Unadjusted and adjusted risk factor associations for Influenza A Virus (IAV) detection* among patients with severe acute respiratory illness in the Hanoi area, 2017–2019.
| Risk factors | Total No. (%) | IAV+ n = 119 (%) | Unadjusted OR (95% CI)† | Adjusted‡ OR (95% CI) |
|---|---|---|---|---|
| Gender§ | ||||
| Male | 128 (36.8) | 44 (37.6) | 1.0 (0.6–1.7) | -- |
| Female | 217 (62.4) | 73 (62.4) | Reference | -- |
| Age quartiles (Q)‖ | ||||
| 15–24 yrs (Q1) | 77 (25.5) | 29 (26.4) | Reference | -- |
| 25–34 yrs (Q2) | 75 (24.8) | 29 (26.4) | 1.0 (0.5–2.1) | -- |
| 35–56 yrs (Q3) | 79 (26.2) | 25 (22.7) | 0.8 (0.4–1.6) | -- |
| ≥ 57 yrs (Q4) | 71 (23.5) | 27 (24.5) | 1.0 (0.5–2.1) | -- |
| Year of study enrollment | ||||
| 2017 | 210 (60.3) | 79 (66.4) | 1.2 (0.7–2.0) | -- |
| 2018 | 103 (29.6) | 35 (29.4) | Reference | -- |
| 2019 | 35 (10.1) | 5 (4.2) | 0.3 (0.1–1.0) | -- |
| Hospital type | ||||
| Military | 151 (43.4) | 65 (54.6) | 2.0 (1.2–3.2) | 2.0 (1.2–3.2) |
| Civilian | 197 (56.6) | 54 (45.4) | Reference | Reference |
*Influenza A virus detection by real-time RT-PCR with Ct value ≤ 38
†Exact confidence intervals
‡After stepwise, unconditional logistic regression using a saturated model and backward elimination of covariates with p > 0.05
§Gender data missing for some patients (n = 3) removed from calculations
‖Age data missing for some patients (n = 46) removed from calculations