Table 2.

Number of herd tests involving serosurveillance of influenza A virus infection classified by the five production classes from 2010 to 2014

Production class	2010	2011*	2012	2013	2014	Total
Fattening herd	50	79	64	65	47	305
Nucleus herd	52	79	78	82	71	362
Multiplier herd	73	117	152	148	137	627
Conv. sow herd	302	950	996	1047	798	4093
Sow pool	13	63	71	59	50	256
Total	490	1288	1361	1401	1103	5643

^*A change in sampling strategy beginning in 2011 where the same herd could be tested more than once in the same year. Sampling took place at the slaughterhouses.