Monitoring COVID-19 and Influenza: The Added Value of a Severe Acute Respiratory Infection Surveillance System in Portugal

Table 5

Cross-correlation analysis between severe acute respiratory infection cases (n = 3,563), (1) COVID-19 cases (n = 2,367,770) and (2) influenza cases (n = 4,174). North and Lisbon and Tagus Valley regions, 28 September 2021–22 May 2022.

Lag	(1) COVID-19					(2) Influenza
	SARI	Influenza-like illness	Cardiovascular diagnosis	Respiratory diagnosis	Respiratory infection	SARI	Influenza-like illness	Cardiovascular diagnosis	Respiratory diagnosis	Respiratory infection
−5	0.38	−0.09	0.10	−0.15	0.35	−0.08	−0.24	0.08	0.08	−0.07
−4	0.50	−0.14	0.04	−0.20	0.50	−0.18	−0.07	0.20	0.12	−0.23
−3	0.62	−0.18	0.00	−0.24	0.64	−0.22	−0.01	0.31	0.11	−0.32
−2	0.71	−0.22	0.06	−0.31	0.73	−0.20	0.08	0.43	0.07	−0.35
−1	0.80	−0.25	0.12	−0.35	0.81	−0.19	0.05	0.44	−0.08	−0.33
0	0.78	−0.38	0.07	−0.37	0.82	−0.20	0.06	0.37	−0.18	−0.31
1	0.59	−0.45	−0.04	−0.35	0.69	−0.22	0.13	0.24	−0.24	−0.28
2	0.35	−0.49	−0.13	−0.26	0.48	−0.28	0.07	0.10	−0.30	−0.28
3	0.11	−0.37	−0.15	−0.09	0.22	−0.31	0.00	0.03	−0.33	−0.27
4	−0.13	−0.20	−0.09	0.02	−0.07	−0.28	−0.02	0.02	−0.32	−0.24
5	−0.29	−0.09	0.03	0.13	−0.29	−0.25	−0.08	−0.02	−0.33	−0.19

SARI: severe acute respiratory infection; COVID-19: coronavirus disease. Values corresponding to Pearson correlations (lag = 0) are highlighted in bold.