Table 4. Comparison of clinical characteristics of respiratory syncytial virus-positive and influenza-positive groups with a group negative for any respiratory virus using multinomial analysis, Portugal, 2010–2018 (n = 5,484 persons).

Clinical characteristics	Viral respiratory infection^a
	RSV			Influenza
	RRR	95% CI	p value	RRR	95% CI	p value
Sudden onset of symptoms	1.2	0.8–1.8	0.361	1.2	1.08–1.43	0.002
Symptoms
Fever or feverishness	0.6	0.4–0.8	0.002	3.3	2.7–4.1	< 0.0001
Malaise	0.7	0.4–1.19	0.114	1.2	1.0–1.5	0.036
Headache	0.8	0.6–1.1	0.265	1.6	1.4–1.8	< 0.0001
Myalgia	0.5	0.3–0.7	< 0.0001	1.7	1.4–2.0	< 0.0001
Cough	4.1	2.1–8.1	< 0.0001	3.6	3–4.4	< 0.0001
Sore throat	1.3	0.9–1.9	0.112	1.1	1–1.3	0.108
Shortness of breath	1.8	1.3–2.5	< 0.0001	0.7	0.6–0.8	< 0.0001
Case definition
ILI	1.4	1.0–2.1	0.063	1.5	1.3–1.7	< 0.0001
ARI-like	1.5	1.0–2.2	0.044	1.4	1.3–1.6	< 0.0001
One respiratory symptom	10.1	1.4–73	0.022	2.8	2.0–3.9	< 0.0001

ARI: acute respiratory infection; CI: confidence interval; ILI: influenza-like illness; RRR: relative risk ratio; RSV: respiratory syncytial virus.

^a Comparison with the reference group, which comprises individuals testing negative for any respiratory virus.

All persons were detected through the Portuguese sentinel Influenza Surveillance System.