Sendai virus. Coloured transmission electron micrograph (TEM) of Sendai virus particles (virions, green). The protein coat (capsid) of one of the particles has split, allowing its RNA (ribonucleic acid) genetic material (green strips) to spill out. The Sendai virus is a paramyxovirus. Also known as parainfluenza virus type 1, it infects mice, rats, hamsters and guinea pigs. It is transmitted by direct contact and in the air, causing laboured breathing and a decrease in the number of offspring produced. The Sendai virus is also used as a cell-fusing agent in laboratories. Magnification unknown.