morbilliviruses

Morbilliviruses are a genus within the family Paramyxoviridae, order Mononegavirales. They are enveloped, single-stranded, negative-sense RNA viruses with a genome of about 15,700 nucleotides. Members infect a wide range of mammals and are notable for causing systemic, highly contagious diseases such as measles in humans and distemper in carnivores.

The genus includes several important pathogens, including the measles virus (Measles morbillivirus) and canine distemper virus (Canine morbillivirus), as well as peste des petits ruminants virus and the historically significant rinderpest virus, which was declared eradicated in 2011. The host range spans humans, domestic animals, and wildlife, and cross-species transmission has been observed in multiple outbreaks.

Transmission is primarily through respiratory droplets and close contact, with high contagion in many settings. Clinical outcomes vary by species, but measles typically presents with fever, cough, conjunctivitis, and rash, while distemper in animals can involve respiratory, gastrointestinal, and neurological signs. The viruses often cause immunosuppression, increasing susceptibility to secondary infections, and can disseminate to multiple organ systems.

Virions display surface glycoproteins H and F, which mediate attachment and fusion with host cells. The genome encodes the nucleocapsid protein N, phosphoprotein P, matrix protein M, fusion protein F, attachment protein H, and polymerase L, with the P gene producing additional proteins V and W by RNA editing and the C protein by alternative translation. Replication occurs in the cytoplasm and virions assemble at the plasma membrane.

Vaccination and control efforts have reduced disease burden: humans rely on measles vaccines, while animal vaccines target canine distemper and other morbilliviruses such as PPR. Eradication programs have succeeded for rinderpest, illustrating the impact of coordinated vaccination and surveillance.