The Flu Epidemic

There are three types of influenza viruses that infect humans - A, B, and C but many different strains of each type. The diseases caused by these viruses are communally referred to as the flu. Haemagglutinin (HA), a viral surface glycoprotein, is a subtype of influenza A. There are 16 known haemagglutinin, however, only three of these subtypes originate in humans: H1, H2, and H3. Each specific haemagglutinin specializes in finding specific sugars in our respiratory tract therefore; the infection appears within our respiratory tract when we contract the flu. Haemagglutinin is a primary target of neutralizing antibodies. Neutralizing antibodies against the flu mirror the function of haemagglutinin by blocking the binding of it to cell’s surfaces. Currently the subtypes of influenza A viruses found in people are H1N1 and H3N2. Influenza A (H1N1), influenza A (H3N2), and influenza B viruses are encompassed in the present day influenza vaccines. Each seasonal influenza vaccine contains antigens representing these three variant virus strains. Influenza vaccines may be administered via an injection also referred to as the flu shot, or as a nasal spray.

Avian influenza also referred to as H5N1 was the last circulating flu virus. H5N1 causes human infections usually following direct or close contact with infected poultry. H5N1 first infected humans in 1997 during a poultry outbreak in Hong Kong. It reemerged in 2003 and 2004 spreading from Asia to Europe to Africa ultimately resulting in millions of infections. The seasonal influenza vaccination does not appear to protect against H5N1 infection.