Table 3. Swine and human influenza viruses: HI antigenic characterization of H3 strains.

		HI titer of serum against:
Virus origin	Virus strain	A/Sw/It/79604/06 (H3N2)*	A/Brisbane/10/07 (H3N2)*
Swine	A/Sw/It/79604/06, H3N2	2560	<10
	A/Sw/It/32242/06, H3N2 ∧	1280	<10
	A/Sw/It/20319/06, H3N2∧	1280	<10
	A/Sw/It/186423/07, H3N2∧	640	<10
	A/Sw/It/206453/07, H3N2∧	1280	<10
	A/Sw/It/319388/07, H3N2∧	1280	<10
	A/Sw/It/209720/08, H3N2∧	1280	<10
	A/Sw/It/136775/08, H3N2∧	1280	<10
	A/Sw/It/120014/08, H3N2∧	1280	<10
	A/Sw/It/117304/08, H3N2∧	640	<10
	A/Sw/It/235509/08, H3N2∧	640	<10
Human	A/Uruguay/716/07, H3N2	<10	2560

HI, Haemagglutination inhibition.

^*Chicken hyperimmune antiserum.

Virus strains used to test swine workers’ and controls’ sera are underlined.

^∧SIVs strains isolated from pigs, in the farms under study.