Table 3.

Sign and significance of the case-control and cross-sectional studies of HPAI H5N1, grouped by type of factors: +++, ++, and + refer to positive association with HPAI H5N1 presence significant at the p-level of < 0.001, < 0.01 and <0.05, respectively; conversely, minus sign are coded in the same way, but reflects negative association with HPAI H5N1 outcomes. Significance code and signs are presented in the same sequence as the corresponding references.

Risk Factors	Significance / Sign	Country	Reference(s)
Farming / Biosecurity
Chicken and ducks in different shelters	− −	Bangladesh	Biswas et al. (2009)
Feeding with slaughter remnants of purchased chickens	+	Bangladesh	Biswas et al. (2009)
Bird slaughtering in live bird markets	+	Indonesia	Indriani et al. (2010)
Clear Zoning in LBM	−	Indonesia	Indriani et al. (2010)
Daily Solid Waste disposal	−	Indonesia	Indriani et al. (2010)
Slaughterhouses in Subdistrict	++	Thailand	Tiensin et al. (2009)
Purchase of live poultry from another farm	+++, ++	Thailand, Nigeria	Paul et al. (2011), Fasina et al. (2011)
Use of disinfectant to clean poultry area	−	Thailand	Paul et al. (2011)
Receive visitors on premises	++	Nigeria	Fasina et al. (2011)
Workers live outside premises	++	Nigeria	Fasina et al. (2011)
Time spent with the fighting cock	− −	Thailand	Paul et al. (2011)
Poultry / livestock
Poultry flock density	++	Vietnam	Henning et al. (2009)
Poultry density	− − −	Indonesia	Yupiana et al. (2010)
Native chickens density	+++, − − −, +/−1, +++	Thailand	Gilbert et al. (2006), Tiensin et al. (2009), Paul et al. (2010), Paul et al. (2011)
Chicken density	+, +/−, − − −, +++	Vietnam, World, China, South Asia	Pfeiffer et al. (2007), Hogerwerf et al. (2010), Martin et al. (2011), Gilbert et al. (2011)
Number of commercial chickens	++	Bangladesh	Loth et al. (2010)
Free-grazing duck density/ domestic duck density / domestic waterfowl density	+++,+,+++,+++,+,+++,++,+++	Thailand, Vietnam, World, China, South Asia	Gilbert et al. (2006), Pfeiffer et al. (2007), Gilbert et al. (2008), Tiensin et al. (2009), Paul et al. (2010), Hogerwerf et al. (2010), Martin et al. (2011), Gilbert et al. (2011)
Density of farm ducks	+	Thailand	Paul et al. (2010)
Duck by chicken density	+	Global	Hogerwerf et al. (2010)
Cock density	+++, ++, +/−	Thailand	Gilbert et al. (2006), Tiensin et al. (2009), Paul et al. (2010)
Quail flocks in subdistrict	+	Thailand	Tiensin et al. (2009)
Buffalo density	− − −	Vietnam	Henning et al. (2009)
Anthropogenic
Human population density	+++, ++, ++/− −, +, +++, +++, +++	Thailand, Vietnam, Bangladesh, China, South Asia, Indonesia	Gilbert et al. (2006), Gilbert et al. (2008), Tiensin et al. (2009), Loth et al. (2010), Yupiana et al. (2010), Martin et al. (2011)
Urban population density	++	Indonesia	Loth et al. (2011)
Rural population density	++	Indonesia	Loth et al. (2011)
Agricultural population density	+	Global	Hogerwerf et al. (2010)
Population density > 100 person / km2	N.A.	South Asia	Adhikari et al. (2009)
Distance to the nearest city	+/−, −, −, −	Thailand, Indonesia	Pfeiffer et al. (2007), Paul et al. (2010), Paul et al. (2011), Loth et al. (2011)
Min. distance to highway	− − −, +, − − −, − − −	China, Thailand, China, China	Fang et al. (2008), Paul et al. (2010), ChunXiang et al. (2010)
Roads density, presence of a road, road length	++, +, +, +++, +++	Bangladesh, Thailand, Romania, Indonesia	Ward et al. (2008b), Loth et al. (2010), Paul et al. (2010), Yupiana et al. (2010), Loth et al. (2011)
Socio-Economic
% Housholds with electricity	− −	Vietnam	Henning et al. (2009)
Purchasing power per capita	−	Global	Hogerwerf et al. (2010)
Wild Birds
Contact with resident birds	+	Bangladesh	Biswas et al. (2009)
Rivers / Lakes / Wetlands
Access to water	+	Bangladesh	Biswas et al. (2009)
Min. distance to lake*Min distance to wetland	− − −	China	Fang et al. (2008)
Min. distance to reservoir / river / lake	−	China	ChunXiang et al. (2010)
Presence of a river stream, or flooded land area	++	Romania	Ward et al. (2008b)
Proportion of land occupied by water	−, +	Indonesia, China	Yupiana et al. (2010), Martin et al. (2011)
Presence of a pond or canal around farmhouse	+++	Thailand	Paul et al. (2011)
Mixosaline water (for wetlands only)	+++	Europe	Iglesias et al. (2010)
Eco-climatic
Mean annual temperature range 21–26°C	N.A.2	SouthAsia	Adhikari et al. (2009)
January minimum temperatures (WB3)	+++	Europe	Si et al. (2010)
Annual precipitation	− − −	China	Fang et al. (2008)
January precipitations (WB)	− − −	Europe	Si et al. (2010)
May–Oct NDVI	−, ++	Vietnam	Pfeiffer et al. (2007), Henning et al. (2009)
March NDVI (WB)	+++/− − −	Europe	Si et al. (2010)
December NDVI (WB)	+++	Europe	Si et al. (2010)
High variation in NDVI	N.A., N.A.	SouthAsia, North Africa	Adhikari et al. (2009), Williams & Peterson (2009)
High NDVI	N.A.	North Africa	Williams & Peterson (2009)
Land use and cropping
Cropping intensity	+++, +, +++	Thailand, Vietnam, Indonesia	Gilbert et al. (2008), Paul et al. (2010), Loth et al. (2011)
% land used for rice	+	Vietnam	Pfeiffer et al. (2007)
% area used for aquaculture	+	Vietnam	Pfeiffer et al. (2007)
Sweet potato yield	− − −	Vietnam	Henning et al. (2009)
Forestry (for wetlands)	+++	Europe	Iglesias et al. (2010)
Topography
Elevation	− − −/+++, −/+, − − −, − −/++, −/+, − − −, − − −, − − −	Thailand, Vietnam, Europe, Indonesia	Gilbert et al. (2006), Pfeiffer et al. (2007), Gilbert et al. (2008), Tiensin et al. (2009), Paul et al. (2010), Si et al. (2010), Paul et al. (2011), Loth et al. (2011)
Low slope	N.A.	South Asia	Adhikari et al. (2009)

¹the signs of −/+ refers to the signs of the single and quadratic term in linear models;

²N.A.: Not applicable because the method does not provide a significance p-value;

³WB: studies where only wild bird HPAI H5N1 data were analysed.