Virulent Newcastle disease (VND), formerly exotic Newcastle disease, is a contagious viral avian disease affecting many domestic and wild bird species; it is transmissible to humans. Though it can infect humans, most cases are non-symptomatic; rarely it can cause a mild fever and influenza-like symptoms and/or conjunctivitis in humans. Its effects are most notable in domestic poultry due to their high susceptibility and the potential for severe impacts of an epizootic on the poultry industries. It is endemic to many countries. No treatment for VND is known, but the use of prophylactic vaccines and sanitary measures reduces the likelihood of outbreaks. The disease is caused by Newcastle disease virus (NDV), an avulavirus. Strains of Newcastle disease virus have been used to treat cancer in humans, since the virus appears to preferentially infect and kill cancerous cells. Strains of Newcastle disease virus have also been used to create viral vector vaccine candidates against Ebola and Covid-19. History Newcastle disease was first identified in Java, Indonesia, in 1926, and in Newcastle-upon-Tyne, England, in 1927. However, it may have been prevalent as early as 1898, when a disease wiped out all the domestic fowl in northwest Scotland. The policy of slaughter ceased in England and Wales on 31 March 1963, except for the peracute form of Newcastle disease and for fowl plague. In Scotland the slaughter policy continued for all types of fowl pest. Interest in the use of NDV as an anticancer agent has arisen from the ability of NDV to selectively kill human tumour cells with limited toxicity to normal cells. Since May 2018, California Department of Food and Agriculture staff and the United States Department of Agriculture have been working on eliminating VND in South California and more than 400 birds have been confirmed to have VND. On February 27, 2019, the California state veterinarian, Annette Jones, increased the quarantine area in Southern California and on March 15, 2019 and April 5, 2019, cases of VND in Northern California and Arizona respectively. Causal agent The causal agent, Newcastle disease virus (NDV), is a variant of avian orthoavulavirus 1, a negative-sense, single-stranded RNA virus. NDV belongs to the subfamily Avulavirinae, which infect birds. Transmission occurs by exposure to faecal and other excretions from infected birds, and through contact with contaminated food, water, equipment, and clothing. Strains NDV strains can be categorised as velogenic (highly virulent), mesogenic (intermediate virulence), or lentogenic (nonvirulent).