Influenza virus H3N2 strain. 3D illustration showing surface glycoprotein spikes hemagglutinin (orange) and neuraminidase (green) on an influenza (flu) virus particle. Haemagglutinin plays a role in attachment of the virus to human respiratory cells. Neuraminidase plays a role in releasing newly formed virus particles from an infected cell. H3N2 viruses are able to infect birds and mammals as well as humans. They often cause more severe infections in the young and elderly than other flu strains and can lead to increases in hospitalisations and deaths.