A previously unknown disease which has spread among broiler farms in Pakistan attacks well grown 3–5 week old chickens causing 60–70% mortality. At autopsy the most prominent lesion is hydropericardium, hence the name hydropericardium syndrome. The disease is believed to be caused by a hitherto unreported virus, but one that only becomes activated when there is coinfection with an adenovirus. The results of studies on various aspects of the syndrome are highlighted, including aetiology, pathology, epidemiology, diagnosis and control. Areas requiring further research are identified.
