Asian flu viruses. Coloured transmission electron micrograph (TEM) of virions (virus particles) of Asian influenza. Each virion (orange) comprises RNA genetic material (not seen) enclosed in a capsid (protein coat). The capsid is covered with spikes of the antigens haemagglutinin and neuraminidase. These help the virus to enter cells in the body. Once inside a cell, it hijacks the cell's machinery and forces it to make more copies of the virus. Asian flu was responsible for thousands of deaths in an outbreak in 1957. Symptoms include fever, weakness and headaches. Magnification: x130,000 when printed 10cm wide.