Table 1.

Wald test: the most influential variables predicting norovirus laboratory reports in respective age- and region-specific models.

Syndromic data		Norovirus activity	P value
Variables Granger-causing norovirus laboratory reports
	NHSa 111 calls due to vomiting among individuals aged 5-14 years	Laboratory reports among individuals aged 25-44 years	.002
	NHS 111 calls due to vomiting among individuals aged 0-4 years	Laboratory reports among individuals aged 0-4 years	.001
	GPb visits due to vomiting among individuals aged 0-4 years	Laboratory reports among individuals aged 45-64 years	.001
	GP visits due to vomiting among individuals aged ≥65 years	Laboratory reports from the West Midlands	.001
	Views of Wikipedia’s Gastroenteritis page	Laboratory reports among individuals aged ≥65 years	<.001
	Views of Wikipedia’s Gastroenteritis page	Laboratory reports from the East of England	<.001
	Search term “norovirus contagious”	Laboratory reports among individuals aged 25-44 years	.002
	Search term “norovirus first symptoms”	Laboratory reports from the East of England	.001
	Search term “norovirus”	Laboratory reports from the East of England	.002
	Search term “norovirus incubation period”	Laboratory reports from London	.001
	Search term “stomach bug”	Laboratory reports among individuals aged 0-4 years	.002
	Search term “stomach pain”	Laboratory reports from the North East	<.001
Granger-causing significant both ways
	NHS 111 calls due to vomiting among individuals aged 25-44 years	Laboratory reports among individuals aged 0-4 years	.002
	Views of Wikipedia’s Gastroenteritis page	Laboratory reports from the South East	<.001

^aNHS: National Health Service.

^bGP: general practice.