Adenovirus in aquatic mammals (otarine adenovirus) is poorly understood. Otarine Adenovirus 1 has been isolated and shown to cause a fulminant hepatitis with fatality in sea lions. The route of transmission is not well understood, but in one aquarium in Japan, a California sea lion, a South African sea lion, and a fur seal were all infected. Healthy aquatic mammals can show evidence of the adenovirus in the intestinal tract with no progression to disease. More study is needed in this area.