Table 2.

Estimated weekly call volume to a national nurse triage line (20% attack rate; 1968- and 1957-like pandemics)^a

Types of Calls	Calls, by Type, at Peak Week of Pandemic
	1968-like Pandemicb		1957-like Pandemicb
	Low Estimatea,c	High Estimatea,c	Low Estimatea,c	High Estimatea,c
Information only calls	623,856	1,416,609	1,169,731	2,833,217
Symptomatic calls	580,404	1,317,939	1,088,257	2,635,879
Subtotals: Calls requiring response from information specialist or healthcare professionald	1,204,260	2,734,548	2,257,988	5,469,096
Calls ended after recorded message or ended prematurely	347,621	789,354	651,790	1,578,708
Totals all calls at peak	1,551,882	3,523,902	2,909,778	7,047,804

^aUsing a seed starting of 10 cases, duration of pandemic lasts up to 45 weeks, for a 20% attack rate (Appendix 2). Estimates based on US population size of approximately 323 million (Table 1).

^b1968-like pandemic = severity level 3; 1957-like pandemic = severity level 4 (Table 1).

^cLow and high estimates for call-to-hospitalization ratio model derived from lower and upper estimates of hospitalization rates, which depend on influenza severity rate, or pandemic type (Table 1).

^dSubtotals represent those calls to a national nurse triage line for caller seeking either additional information regarding pandemic influenza or those with symptoms seeking advice regarding treatment. Such calls require operator assistance and response.