An isolant of duck plague herpesvirus from the Lake Andes Refuge outbreak was seeded in raw and filter-decontaminated water from two locations on the refuge, held at 4 C, and assayed for infectivity intermittently over a period of 2 mo. From an initial level of about 105 PFU per ml, infectivity in the filtered samples uniformly dropped to about 104 PFU per ml. Infectivity in the raw samples declined much more rapidly; infectious virus remaining at the end of 2 mo (ca. 101 PFU per ml) was only about 0.01% of that originally seeded.
