INFECTION OF HUMANS AND HORSES BY A NEWLY DESCRIBED MORBILLIVIRUS

Objective: to describe the clinical and epidemiological features of an outbreak of a viral infection affecting humans and horses. Setting: S tables in Hendra, a suburb of Brisbane. Subjects: affected horses and humans, and at-risk human contacts. Results: A pregnant mare died two days after arrival from a paddock elsewhere in Brisbane. Eight to 11 d ays later, illness (depression, anorexia, fever, dyspnoea, ataxia, tac hycardia, tachypnoea and nasal discharge) was reported among 17 other horses from the same or an adjoining stable. Fourteen horses died or w ere put down. five and six days after the index mare's death, a stable -hand and then a horse trainer, both of whom had had close contact wit h the sick mare's mucous secretions, developed influenza-like illnesse s. The stable-hand recovered out the the trainer developed pneumonitis , respiratory failure, renal failure and arterial thrombosis, and died from a cardiac arrest seven days after admission to hospital. A morbi llivirus cultured from his kidney was identical to one isolated from t he lungs of five affected horses. The two affected humans and eight ot her horses were seropositive for the infection, which was reproduced i n healthy horses following challenge by spleen/lung homogenates from i nfected horses. There was no serological evidence of infection in 157 humans who had had contact with the stables or the sick horses or huma ns. Conclusions: A previously undescribed morbillivirus infected a pro bable 21 horses and two humans; one human and 14 horses died. That no further cases were detected among humans suggests that the virus was o f low infectivity. The source of infection remains undetermined.