Developing guidelines for school closure interventions to be used during a future influenza pandemic

BMC Infectious Diseases

Table 1 Relationship between activation trigger, cumulative diagnosed cases and intervention activation delay.

		R₀
Activation trigger		1.5		2.0		2.5
Cases diagnosed per day	% of population diagnosed per day	Cumulative diagnosed cases (%)	Activation delay in days	Cumulative diagnosed cases (%)	Activation delay in days	Cumulative diagnosed cases (%)	Activation delay in days
1	0.003	1 (0.003)	5	1 (0.003)	5	1 (0.003)	5
5	0.017	19 (0.063)	14	14 (0.047)	11	12 (0.04)	9
10	0.033	53 (0.177)	20	40 (0.133)	14	31 (0.104)	11.5
15	0.05	97 (0.33)	24	60 (0.2)	16	48 (0.16)	13
20	0.067	136 (0.45)	26	83 (0.277)	17	68 (0.227)	14
25	0.083	190 (0.63)	28	109 (0.364)	18	85 (0.284)	14.5
30	0.1	237 (0.79)	30	136 (0.454)	19	99 (0.33)	15
40	0.13	335 (1.12)	33	188 (0.627)	20	140 (0.467)	15.5
50	0.167	454 (1.52)	36	235 (0.784)	21	179 (0.597)	16
60	0.2	586 (2.0)	38	288 (0.96)	21.5	214 (0.714)	16.5
70	0.233	708 (2.4)	40	345 (1.15)	22	245 (0.817)	17
80	0.267	848 (2.83)	42	409 (1.364)	23	298 (0.994)	17.5
90	0.3	958 (3.2)	43	447 (1.49)	23.5	342 (1.14)	18
100	0.333	1107 (3.7)	45	528 (1.76)	24	366 (1.22)	18.5

The table shows a range of daily diagnosed case(s) in the community, which our simulations use as school closure activation triggers. It relates the activation trigger to the proportion of population newly diagnosed per day, the cumulative number of diagnosed cases, and the consequent delay in intervention corresponding to each activation trigger, for three different simulated epidemics with R₀ values of 1.5, 2.0 and 2.5.
For a number of daily diagnosed cases to count towards the intervention activation, it is assumed that the following sequence of events occurs:
i) The individual becomes infected with the pandemic strain.
ii) The individual experiences significant symptoms.
iii) They seek medical attention.
iv) The infection is identified as pandemic influenza strain.
v) The case should is reported to a public health monitoring scheme.
The diagnosis ratio (or ascertainment efficiency) is assumed such that 50% of the symptomatic cases should be diagnosed following the conditional probability that event e) occurs given that both a) and b) have occurred. A further assumption is that there are no false positive reports during pandemic influenza.

ISSN: 1471-2334