Timeline of human flu-strain infections The European avian flu outbreak is caused by a H5N8 subtype of the Influenza Type A virus. Subtypes are categorised by two proteins on the surface of the virus – haemagglutinin (HA) and neuraminidase (NA) ---------------------------------------- Influenza Type A Haemagglutinin: Rod-shaped spikes of glycoprotein (GP) responsible for viral penetration into host cell Neuraminidase: Mushroom-shaped spikes of GP act as enzyme to break down sialic acids and penetrate mucous membrane of respiratory tract Lipid envelope: Outer membrane supports around 500 spikes of HA and NA proteins M1 matrix: Protein shell gives strength and rigidity Nucleocapsid: Eight segments of single-stranded RNA – genetic material of virus M2 ion channel: Allows acids to enter virusx ---------------------------------------- 17 subtypes of HA – H1, H2, H3, H5, H7, H9 and H10 infect humans 10 subtypes of NA – N1, N2, N3, N7 and N9 infect humans ----------------------------------------- H1N1 1918-19: Spanish flu pandemic kills 20-50 million people worldwide H2N2 1957-58: Asian flu originates in China and spreads globally, killing 1.5 million people H3N2 1968-69: Hong Kong flu pandemic of “variant” of H2N2 kills up to 750,000 people worldwide H5N1 1997: First time an influenza virus is found to be transmitted directly from birds to people. 18 people infected in Hong Kong – six fatalities H9N2 1999: New bird flu strain appears in humans – no fatalities H7N2 2002: Infection found in one person in U.S. following poultry outbreak H7N7 2003: New bird flu strain infects 89 people in Netherlands – one fatality H7N3 2004: New strain detected in humans – two poultry workers in Canada H10N7 2004: New bird flu strain detected in humans – two infants in Egypt H5N1 2007: 88 cases in Southeast Asia and Nigeria, 59 fatalities reported H1N1 2009: Swine flu pandemic spreads to more than 70 countries, killing 23,500 people, 12,500 in U.S. H7N9 2013: New avian flu crosses to humans. 443 cases in China, Hong Kong, Taiwan and Malaysia – unofficial death toll of 127 -------------------------------------------- Sources: CDC, ECDC, NIAID, News-Medical.Net Picture: CDC words 365