Text Size:AAA

Influenza A H3N2 General Information

During 1998, severe outbreaks of influenza were observed in four swine herds in the United States. This event was unique because the causative agents, H3N2 influenza viruses, are infrequently isolated from swine in North America. In the second half of 2011, a number of U.S. residents were found to be infected with influenza A variant viruses, primarily H3N2. Investigations revealed human infections with these viruses following contact with swine as well as limited human-to-human transmission.

H3N2 is a subtype of the influenza virus A. Influenza A H3N2 Viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains. By reassortment, influenza A H3N2 exchanges genes for internal proteins with other influenza subtypes. It is an important cause of human influenza. Influenza A H3N2 variant virus is an influenza virus that contains genes from human, avian and swine origins. Most infections with this virus have resulted in self-limited, mild respiratory illnesses. Influenza A H3N2 virus is very contagious and can cause severe illness especially in patients who are very young or old or have some other medical condition as well. The severity of symptoms can vary but usually involves respiratory and constitutional (e.g. headache, aching muscles) symptoms.

Influenza A H3N2 is increasingly abundant in seasonal influenza, which kills an estimated 36,000 people in the United States each year. Each seasonal Influenza A H3N2 flu is slightly different from one of last year's H3N2 variants. Seasonal influenza viruses flow out of overlapping epidemics in East and Southeast Asia, then trickle around the globe before dying off.

While influenza A H3N2 viruses have been detected in U.S. swine, it's unknown how widespread they are in swine herds. It's possible that sporadic infections and even localized outbreaks among people with H3N2 will continue to occur. While there is no evidence that sustained human-to-human transmission is occurring, all influenza viruses have the capacity to change and it's possible that this virus may become widespread. So far, the severity of illnesses associated with H3N2 in people has been similar to the severity of illnesses associated with seasonal flu virus infections. Limited serologic studies indicate that adults may have some pre-existing immunity to this virus while children do not.

Flu vaccines are based on predicting which mutants of H1N1, H3N2, H1N2, and influenza B will proliferate in the next season. Separate vaccines are developed for the northern and southern hemispheres in preparation for their annual epidemics. In the tropics, influenza shows no clear seasonality. In the past ten years, H3N2 has tended to dominate in prevalence over H1N1, H1N2, and influenza B. Measured resistance to the standard antiviral drugs amantadine and rimantadine in H3N2 has increased from 1% in 1994 to 12% in 2003 to 91% in 2005. An A/Perth/16/2009-like H3N2 virus is included in the 2010-11 seasonal influenza vaccine. Perth-like H3N2 viruses were first identified in early 2009, but have not yet circulated widely in the United States. Past influenza vaccines did not contain this strain, so vaccination with last year’s seasonal vaccine would not be expected to provide substantial protection against this H3N2 Perth-like strain.

Influenza Research Reagents (Hot!)

Influenza virus antigen protein
Product Name Cat No.
Influenza H1N1 (A/California/07/2009) Hemagglutinin 11085-V08H
Influenza H1N1 (A/Puerto Rico/8/1934) Hemagglutinin 11684-V08H
Influenza H1N1 (A/California/04/2009) Hemagglutinin 11055-V08H
Influenza H1N1 (A/California/04/2009) Hemagglutinin 11055-V08B
Influenza H3N2 (A/Aichi/2/1968) Hemagglutinin 11707-V08H
Influenza H3N2 (A/Brisbane/10/2007) Hemagglutinin 11056-V08H
Influenza H5N1 (A/Anhui/1/2005) Hemagglutinin 11048-V08H1
Influenza H3N2 Virus Hemagglutinin Protein 40043-V08H
Influenza H7N9 (A/Anhui/1/2013) Hemagglutinin Protein 40103-V08B
Influenza H1N1 (A/Brisbane/59/2007) Hemagglutinin 11052-V08H
Influenza H5N1 (A/VietNeuraminidasem/1194/2004) Hemagglutinin 11062-V08H1
Influenza H7N9 (A/Anhui/1/2013) Hemagglutinin Protein 40103-V08H
Influenza H5N1 (A/Anhui/1/2005) Hemagglutinin 11048-V08H4
Influenza H1N1 (A/California/07/2009) Hemagglutinin Protein 11085-V08B
Influenza H1N1 Nucleoprotein Protein 11675-V08B
Influenza H1N1 (A/California/07/09) Nucleoprotein Protein 40205-V08B
Influenza H1N1 (A/California/04/2009 )Neuraminidase Protein (Active) 11058-V07B
Influenza H5N1 Neuraminidase (Active) 11676-VNAHC
Influenza H5N1 (A/Hubei/2011) Neuraminidase Protein (Active) 40018-V07H
Influenza H1N1 (A/Puerto Rico/8/34/Mount SiNeuraminidasei) Matrix Protein 1 40010-V07E
Influenza virus antigen antibody
Product Name Cat No.
Influenza H1N1 (Swine Flu 2009) Hemagglutinindy Antibo 11055-MM01
Influenza H1N1 (Swine Flu 2009) Hemagglutinin Antibody 11055-RM05
Influenza H7N9 Hemagglutinin Antibody, Rabbit Pab 40103-RP02
Influenza H1N1 (Swine) Hemagglutinin Antibody 11055-MM09
Influenza H1N1 Hemagglutinin Antibody 11684-RP01
Influenza H1N1 (Swine Flu 2009) Hemagglutinin Antibody 11055-RP02
Influenza H5N1 (Avian Flu) Hemagglutinin Antibody 11048-MM01
Influenza Virus Hemagglutinin Antibody, Rabbit MAb 86001-RM01
Influenza H3N2 Hemagglutinin Antibody 11056-MM03
Influenza H1N1 (Swine Flu 2009) Neuraminidase Antibody 11058-R001