Human parainfluenza virus. Coloured transmission electron micrograph (TEM) of a section through a human parainfluenza virus (HPIV). The white band around the virus is the capsid, or protein coat. Surrounding this is the lipoprotein envelope, which holds spike-like surface proteins. Within the capsid is the coiled RNA (ribonucleic acid) genetic material. HPIV is a paramyxovirus that causes different types of respiratory infections, including ear infections, sore throats, croup, pneumonia and bronchitis. It is most common in children and babies. Magnification: x20,500 when printed at 10 centimetres tall.