A comprehensive review of the epidemiology and disease burden of Influenza B in 9 European countries

Figures & data

Figure 1. PubMed selection procedure and number of included articles.

Table 1. Summary of influenza B burden of disease from the literature review.

			Proportions, n (%)
Country	Season	Population	Laboratory-confirmed influenza	Influenza B	Influenza A	Comments
Switzerland^21	2001–2003	Pediatric patients hospitalized with respiratory symptoms during the cold season (n = 338)				—
		2001–2002 (n = 112)	27 (24.1%)	3 (11.1%)	24 (88.9%)
		2002–2003 (n = 226)	33 (14.6%)	12 (36.4%)	21 (63.6%)
Austria^24	1999–2010	Swabs collected from a subset of patients from sentinel surveillance throughout Austria, and from hospitals, pediatricians and unaffiliated physicians (n = 14,539)				—
		1999–2000 (n = 319)	115 (36.1%)	0 (0.0%)	115 (100%)
		2000–2001 (n = 288)	122 (42.4%)	12 (9.8%)	110 (90.2%)
		2001–2002 (n = 449)	205 (45.7%)	129 (62.9%)	76 (37.1%)
		2002–2003 (n = 874)	510 (58.4%)	45 (8.8%)	465 (91.2%)
		2003–2004 (n = 843)	333 (39.5%)	1 (0.8%)	332 (99.2%)
		2004–2005 (n = 1,087)	440 (40.5%)	171 (38.9%)	269 (61.1%)
		2005–2006 (n = 859)	245 (28.5%)	67 (27.3%)	178 (72.7%)
		2006–2007 (n = 1,827)	430 (23.5%)	4 (0.9%)	426 (99.1%)
		2007–2008 (n = 1,533)	341 (22.2%)	53 (15.5%)	288 (84.5%)
		2008–2009 (n = 1,513)	511 (33.8%)	88 (17.2%)	423 (82.8%)
		2009–2010 (n = 4,974)	1,952 (39.5%)	2 (0.1%)	1,950 (99.9%)
Belgium^20	2009–2010	PediSurv network: Patients aged <5 years presenting with ILI (n=139).	28 (20.1%)	1 (3.6%)	27 (96.4%)	—
		Sentinel surveillance network: Patients with ILI (n = 810)	426 (52.6%)	3 (0.7%)	423 (99.3%)
Finland^22, 27	July 1998-June 2004 ^22	Children aged ≤16 years who were hospitalized with laboratory-confirmed influenza (n = 401)	–	70 (17.5%)	330 (82.3%)	1 (0.2%) child had a combined influenza A and B infection
	Nov 2002-April 2003 ^27	Patients in the Finnish Defence Forces with an upper respiratory infection (n = 302)	135 (34.7%)	109 (80.7%)	26 (19.3%)	—
Greece^23, 25, 26	2009–2012 ^25	Pediatric population of Southern Greece with ILI (n = 7,357)	2,656 (36.1%)	87 (3.3%)	2,569 (96.7%)	—
		2009–2010 (n = 5,137)	1,664 (32.2%)	2 (0.1%)	1,662 (99.9%)
		2010–2011 (n = 1,870)	848 (45.3%)	14 (1.7%)	834 (98.3%)
		2011–2012 (n = 314)	144 (45.9%)	71 (49.3%)	73 (50.7%)
	2005–2008 (Winter seasons; November-May) 26	Pediatric population of Southern Greece with ILI (n = 1,272)2005–2006 (n = 392)2006–2007 (n = 377)2007–2008 (n = 503)	387 (30.4%)69 (17.6%)181 (48.0%)137 (27.2%)	Influenza virus type B was the dominant recovered type for the first season (83.6%), while subtypes A/H3N2 (78.1%) and A/H1N1 (70.8%) dominated the following 2 winter seasons, respectively	Distribution of influenza A and B was only presented in mixed infected cases (21.3%) and not for all virologically confirmed influenza cases
	2002–2005 23	729 hospitalized children aged 6 months–13 years	161 (22.1%)	23 (14.3%)	134 (83.2%)	Remaining 4 (2.5%) cases were combined influenza A and B infections
Czech Republic^39	2012–2013	Patients presenting with ARI or ILI (n = 2,793)	994 (35.6%)	30 (3.0%)	964 (97.0%)	—
Slovakia^40	1993–2008	Laboratory-confirmed influenza cases (n = 1,298)	–	293 (22.6%)	1,005 (77.4%)	Surveillance was sentinel since 2002/2003; before this season only few samples were collected

ARI: acute respiratory infection; ILI: influenza-like illness.

Figure 2. Circulation patterns of seasonal influenza viruses excluding pandemic seasons, 2003–2013* (WHO-FluNet) Flu, influenza; wk, week, *Note: Austria (Data unavailable for 2005–2009); Belgium (Data unavailable for 2006); Luxembourg (Data unavailable for 2003 and 2005); Slovakia (Data unavailable for 2005–2008); Estonia (Data unavailable for 2003–2007).

Table 2. Overview of circulating influenza B lineage, by country, by influenza season.

	Circulating lineage									Recommended vaccine lineage
Season	Switzerland	Austria	Belgium	Luxembourg	Finland	Greece	Czech Republic	Slovakia	Estonia
2012–2013	Vic, Yam^*	-nr-	Vic, Yam^*	-nr-	Vic^*, Yam	-nr-	-nr-	Vic, Yam^*	-nr-	Yam
2011–2012	Vic^*, Yam	Vic^*, Yam	Yam	-nr-	-nr-	Vic, Yam^†	Vic	Vic, Yam^*	-nr-	Vic
2010–2011	Vic^*, Yam	Vic^*, Yam	Vic^*, Yam	-nr-	Vic, Yam^*	Vic, Yam^*	Vic^*, Yam	Vic	-nr-	Vic
2009–2010	Vic^*, Yam	-nr-	Vic^*, Yam	-nr-	-nr-	Vic	-nr-	-nr-	-nr-	Vic
2008–2009	Vic^*, Yam	Vic	Vic^*, Yam	-nr-	Vic	Vic	-nr-	-nr-	-nr-	Yam
2007–2008	-nr-	Yam	-nr-	Yam	-nr-	-nr-	Yam	-nr-	-nr-	Vic
2006–2007	-nr-	-nr-	-nr-	Yam	-nr-	-nr-	-nr-	-nr-	-nr-	Vic
2005–2006	-nr-	Vic^*, Yam	Vic^*, Yam	Yam	-nr-	-nr-	Vic	-nr-	-nr-	Yam
2004–2005	Vic, Yam^*	Vic, Yam^*	Yam	Vic^*, Yam	-nr-	-nr-	Yam	Yam	-nr-	Yam
2003–2004	-nr-	-nr-	-nr-	-nr-	-nr-	-nr-	-nr-	-nr-	-nr-	Vic
2002–2003	Vic	-nr-	-nr-	-nr-	Vic^*, Yam^†	-nr-	Vic	Vic	-nr-	Vic

Note: Data are obtained from EuroFlu and FluNet, unless otherwise specified:

^† Data obtained from peer-reviewed literature: Finland²⁷, Greece²⁵;

* Predominant lineage; Text in bold-face indicate mismatch between predominant circulating influenza B lineage and vaccine lineage; -nr-, not reported; Vic: B/Victoria lineage; Yam: B/Yamagata lineage.

Table 3. Selection procedure.

Step 1. Screening articles by reading titles and abstracts

Inclusion criteria:

• Relevant outcome related to seasonal influenza A/H1N1, A/H3N2, B/Victoria and B/Yamagata • Conducted in, or presented data from at least one of the selected European countries• Presented data from 2003 onward

Exclusion criteria:

• Pandemic influenza • Pharmacokinetic or pharmacodynamics studies • Animal or in vitro studies • Case reports, cases series, clinical trials, or meta-analyses • Articles on pathophysiology, treatment, etiology, or diagnosis • Articles including pneumonia patients as the study population • No abstract provided (full text was checked if the title closely matched the review objective) • Fewer than 30 patients • Case studies

Step 2. Screening of full text articles selected in Step 1.

These articles were either included in the evidence tables or were excluded if the article did not contain relevant information or contained poor quality information. At this stage, critical appraisal of full text articles, using a standard set of criteria, took place. Exclusion criteria:

• A narrative review (e.g., no methods section describing how the authors collected the literature) • Content of the article does not answer any of the review questions, which was unclear during selection step 1 • No quantitative data could be retrieved from the article

Step 3. Screening during data-extraction phase

Further scrutiny of the article during the data-extraction phase possibly leading to exclusion

Meury S, Zeller S, Heininger U. Comparison of clinical characteristics of influenza and respiratory syncytial virus infection in hospitalised children and adolescents. Eur J Pediatr 2004; 163:359-63; PMID:15106003; http://dx.doi.org/10.1007/s00431-004-1445-6

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Redlberger-Fritz M, Aberle JH, Popow-Kraupp T, Kundi M. Attributable deaths due to influenza: a comparative study of seasonal and pandemic influenza. Eur J Epidemiol 2012; 27:567-75; PMID:22678614; http://dx.doi.org/10.1007/s10654-012-9701-y

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Hombrouck A, Sabbe M, Van Casteren V, Wuillaume F, Hue D, Reynders M, Gérard C, Brochier B, Van Eldere J, Van Ranst M, et al. Viral aetiology of influenza-like illness in Belgium during the influenza A(H1N1)2009 pandemic. Eur J Clin Microbiol Infect Dis 2012; 31:999-1007; PMID:21901635; http://dx.doi.org/10.1007/s10096-011-1398-4

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Silvennoinen H, Peltola V, Vainionpää R, Ruuskanen O, Heikkinen T. Incidence of influenza-related hospitalizations in different age groups of children in Finland: a 16-year study. Pediatr Infect Dis J 2011; 30:e24-8; PMID:21298851; http://dx.doi.org/10.1097/INF.0b013e3181fe37c8

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Ikonen N, Pyhälä R, Axelin T, Kleemola M, Korpela H. Reappearance of influenza B/Victoria/2/87-lineage viruses: epidemic activity, genetic diversity and vaccination efficacy in the Finnish Defence Forces. Epidemiol Infect 2005; 133:263-71; PMID:15816151; http://dx.doi.org/10.1017/S0950268804003462

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Melidou A, Exindari M, Gioula G, Malisiovas N. Severity of the two post-pandemic influenza seasons 2010–11 and 2011–12 in Northern Greece. Hippokratia 2013; 17:150-2; PMID:24376321

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Kyncl J, Havlickova M, Nagy A, Jirincova H, Piskova I. Early and unexpectedly severe start of influenza epidemic in the Czech Republic during influenza season 2012–13. Euro Surveill 2013; 18; PMID:23410257

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Seligová J, Culmanová A, Kristufková Z, Cislákova L, Hudecková H. Changes in surveillance of acute respiratory infections including influenza in the Slovak Republic during 1993–2008. Cent Eur J Public Health 2011; 19:20-5; PMID:21526651

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