Ten years (2004–2014) of influenza surveillance in Northern Italy

Figures & data

Table 1. Incidence of influenza-like illness (ILI) (×1000 inhabitants) at peak in the general population and by age group in the last 10 influenza epidemics (from 2004–2005 to 2013–2014) in Lombardy

Season	Incidence of ILI (×1000 inhabitants) at epidemic peak
	General population		Age group
		0–4 y		5–14 y	15–64 y	≥65 y
2004–2005	12.04	26.86		29.81	11.85	5.16
	(2005–06)	(2005–07)		(2005–05)	(2005-–6)	(2005–07)
2005–2006	2.46	10.49		9.22	1.77	0.54
	(2006–12)	(2006–12)		(2006–12)	(2006–11)	(2006–11)
2006–2007	5.14	22.80		12.56	4.40	1.78
	(2007–06)	(2007–06)		(2007–05)	(2007–06)	(2007–07)
2007–2008	5.16	14.54		10.84	5.88	1.69
	(2008–02)	(2008–04)		(2008–04)	(2008–02)	(2008–02)
2008–2009	5.55	16.60		12.03	5.21	2.18
	(2009–05)	(2009–05)		(2009–04)	(2009–05)	(2009–06)
2009–2010	13.28	20.41		43.68	8.85	1.63
	(2009–44)	2009–45		2009–44	(2009–45)	(2009–45)
2010–2011	8.13	17.90		20.22	5.94	1.68
	(2011–05)	(2011–04)		(2011–05)	(2011–05)	(2011–05)
2011–2012	8.47	24.85		16.93	6.60	3.22
	(2012–05)	(2012–04)		(2012–04)	(2012–05)	(2012–06)
2012–2013	8.09	17.38		19.57	6.2	2.19
	(2013–05)	(2013–05)		(2013–05)	(2013–06)	(2013–06)
2013–2014	4.94	12.93		7.96	5.1	1.79
	(2014–06)	(2014–06)		(2014–06)	(2014–06)	(2014–02)

The weeks during which peak incidence was reported are in brackets..

Table 2. Proportion (%) of influenza virus types and subtypes out of total influenza virus detections in Lombardy by season (from 2004–2005 to 2013–2014)

Season	Influenza A(H1N1) virus*	Influenza A(H3N2) virus	Influenza B virus
2004–2005	9%	54%	38%
2005–2006	40%	40%	20%
2006–2007	16%	78%	6%
2007–2008	36%	n.d.	64%
2008–2009	n.d.	92%	8%
2009–2010	78%	n.d.	22%
2010–2011	60%	5%	35%
2011–2012	4%	87%	9%
2012–2013	19%	3%	78%
2013–2014	30%	70%	n.d.

* Referred to as A(H1N1)pdm09 from 2009 onwards; n.d., not detected.

Figure 1. Risk of infection from any influenza virus by age group and by season (from 2004–2005 to 2013–2014). Risk of infection is expressed as a percentage (number of individuals with a laboratory-confirmed influenza virus infection out of the total number of subjects with ILI).

Figure 2. Viral strains included in seasonal influenza vaccine formulations from 2004–2005 to 2013–2014 seasons and their genetic match (identity range) with influenza viruses circulating in Lombardy by season and by type/subtype. (A) A(H1N1) influenza virus (referred to as A[H1N1]pdm09 from 2009 onwards); (B) A(H3N2) influenza virus, and (C) influenza B virus. (n.d., not detected).

Figure 3. Influenza vaccine coverage rates in individuals ≥65 y (vaccine target population) in Lombardy by season (from 2004–2005 to 2013–2014).