Small islands and pandemic influenza: Potential benefits and limitations of travel volume reduction as a border control measure

Table 1 Probability of small islands in the South Pacific escaping a global influenza pandemic (for different values of R ₀and different travel volume reductions for arriving travellers).

Country (year for traveler arrival data)	Total annual traveler arrivals	Island escape probability for global influenza pandemic
		99% travel reduction			79% travel reduction
		R₀ = 1.5	R₀ = 2.25	R₀ = 3.0	R₀ = 1.5	R₀ = 2.25	R₀ = 3.0
Guam (2007/08)	1,210,600†	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
Fiji (2004)	596,084	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
Northern Mariana Islands (2004)	589,244*	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
French Polynesia (2006)	221,549*	0.02	<0.01	<0.01	<0.01	<0.01	<0.01
Samoa (2007)	196,627‡	0.03	<0.01	<0.01	<0.01	<0.01	<0.01
Vanuatu (2006)	154,101§	0.06	<0.01	<0.01	<0.01	<0.01	<0.01
Cook Islands (2007)	109,115	0.14	<0.01	<0.01	<0.01	<0.01	<0.01
New Caledonia (2006)	100,491*	0.16	0.01	<0.01	<0.01	<0.01	<0.01
Palau (2006)	86,375*	0.21	0.02	<0.01	<0.01	<0.01	<0.01
American Samoa (2006)	72,800	0.27	0.04	0.01	<0.01	<0.01	<0.01
Tonga (2003)	63,451¶	0.32	0.06	0.02	<0.01	<0.01	<0.01
Federated States of Micronesia (FSM) (2005)	18,958*	0.71	0.43	0.32	<0.01	<0.01	<0.01
Solomon Islands (2007)	13,748*	0.78	0.54	0.44	<0.01	<0.01	<0.01
Marshall Islands (2005)	9173*	0.85	0.66	0.57	0.03	<0.01	<0.01
Kiribati (2006)	4704#	0.92	0.81	0.75	0.17	0.01	<0.01
Niue (2006)	4588**	0.92	0.81	0.76	0.18	0.01	<0.01
Tuvalu (2007)	1130	0.98	0.95	0.93	0.65	0.34	0.24
Nauru	n/a	-	-	-	-	-	-
Wallis and Futuna	n/a	-	-	-	-	-	-

Notes:
The coding of the island escape probability: standard type, <10%; italics, 10 - 50%; bold, > 50%.
* Available data do not include island citizens returning from overseas travel (i.e., non-citizen arrivals only) though the former are usually a small proportion of arrivals relative to non-citizens for most PICTs.
† For Guam this figure was extrapolated from arrivals data for October 2007 to February 2008. Includes civilian and armed forces arrivals by air (not by sea) and does not include data on returning citizens of Guam.
‡ For Samoa this figure involves an extrapolation of arrivals data for January to July 2007 and includes a figure for returning residents based on the assumption that all Samoan citizens who departed returned in the same year (2005 data). These figures include arrivals by sea (4.4% of total visitor arrivals).
§For Vanuatu this figure includes day visitors from ships (n = 85,922).
¶For Tonga this figure includes an estimate for returning residents and arrivals by ship and yacht.
# For Kiribati this figure includes an estimate for returning residents based on the assumption that all "I-Kiribati" leaving also return in the same year (n = 130 for the most recent year with data i.e., 2002).
** For Niue this figure includes an estimate for returning residents based on the assumption that all "residents not departing permanently" return in the same year.
n/a: No data available.

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