Table 1.

Table 1 Peak Cross-correlation

	ILI		GIID
	Correlation	Lag (Days) ∗	Correlation	Lag (Days) ∗
IFH structured—IFH narrative	0.88 (0.85–0.91)	0	0.51 (0.42–0.59)	(0)
IFH structured—NYC isolates	0.89 (0.76–1.00)	1
IFH narrative—NYC isolates	0.84 (0.71–0.97)	3
IFH structured—NYC ED	0.93 (0.91–0.94)	0	0.81 (0.67–0.94)	(−2)
IFH narrative—NYC ED	0.88 (0.84–0.91)	0	0.47 (0.33–0.61)	(−6)
NYC ED—NYC isolates	0.92 (0.79–1.00)	−1

^∗ A negative number implies the first series in the pair occurred first. The lags for GIID are shown in parentheses because they lacked high peak correlation and good cross-correlation structure, so the values are likely to be unreliable.

ILI = Influenza-like Illness; GIID = Gastrointestinal infectious diseases; IFH = Institute for Family Health; NYC = New York City; NYC ED = New York City Emergency Department.