Possible explanations for why some countries were harder hit by the pandemic influenza virus in 2009 – a global mortality impact modeling study

Morales, Kathleen F.; Paget, John; Spreeuwenberg, Peter

doi:10.1186/s12879-017-2730-0

Table 1 The 48 possible risk factors worth investigating for Influenza A(H1N1)pdm09 mortality through a targeted literature search in Pubmed (with a focus on 2000–2013)^a

From: Possible explanations for why some countries were harder hit by the pandemic influenza virus in 2009 – a global mortality impact modeling study

Factor type	Factor	Factor variable	Association higher^a	Association lower^a	References
Environmental	Pollution	Particulate matter	✓		[28]
	Pollution	Ozone	✓		[28]
	Climate	Low temperature/low humidity	✓		[10, 25, 26]
Physiological comorbidities in adults	Immunosuppression other than HIV	renal disease, chronic disease, cancer, etc.	✓		[5]
	Obesity	BMI > 30	✓		[3, 7]
	Morbid Obesity	BMI > 40	✓		[44]
	Pulmonary Disease	COPD, other	✓		[5]
	Immunosupression	HIV	✓		[57]
		TB	✓
		HIV on ARTs		✓	[57]
Physiological comorbidities in children	Neurological Disorders	Prevalence in children	✓		[11]
	Cerebral Palsy and developmental delay		✓		[13]
	Congenital Heart Disease		✓		[13]
	Asthma and immunosupression		✓		[30, 40]
Treatment	Antiviral Use	Antiviral Drug Distribution		✓	[31]
		Antiviral within 48 h.		✓	[23, 28, 30]
		Late onset antiviral	✓		[3, 31, 32]
Healthcare	Healthcare expenditure	Access to healthcare		✓	[23, 24]
		Prompt treatment and available options		✓
		Physician knowledge and H1N1awareness		✓
Demographics	Population age structure	Preschool age	✓		[9]
		Pediatric patients	✓		[15]
		% < 15	✓		[16]
		% > 60	✓	✓	[16, 17]
		Children at home	✓		[34]
	Ethnicity	Alaskan/A.Indian/New Zealand aboriginal	✓		[71]
		Hipanics and blacks		✓	[13]
		Children of S. Asian descent	✓		[16]
pH1N1 Viral Factors	Strain variation by country	Start of the pandemic	✓		[30, 38, 39]
		Pandemic peak	✓
		Co-circulation	✓	✓
	Viral shedding/ transmission	Longer shedding in younger people	✓		[72]
		Longer shedding under optimal climatic conditions	✓		[26]
		Longer shedding in immunocompromised people	✓		[8, 72]
		Longer shedding or higher viral loads in those with severe disease	✓		[8, 72]
		Shorter shedding in those treated with antivirals within 48 h		✓	[8]
	Disease severity	Pathogenic strains	✓
Data or modelling issues	Variation in case finding by country	-Clinician awareness		✓
		-Diagnostic availability	✓	✓
		-Testing protocol	✓	✓
		-Breadth of surveillance	✓	✓
Pandemic preparedness activities	Policies	Quarantine		✓	[35]
	Activities	Treatment, education		✓
	Case finding efforts	Outreach and method	✓	✓
	Quickness of response	Timing to mobilize community	✓	✓
Other Factors	CDC Multiplier				[43]
Other Factors	International flight traffic	International flights coming and going	✓		[36]

^a “Association Higher” indicates those factors that may be risk factors for mortality. “Association Lower” indicates those factors that may be protective against mortality. Some factors are found to be both risk factors and protective factors in the literature and this is indicated with two check marks in the table

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ISSN: 1471-2334

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