Water-filled plastic freeze-ball (28 mm largest diameter).
The clinical manifestations of infectious hepatitis are well known and easily recognized. Considerable uncertainty exists regarding the true incidence and the degree of variability in the incubation period of this disease. Incidence is difficult to determine because of an unknown number of relatively asymptomatic anicteric patients. Variation in the incubation period is difficult to assess because of lack of information regarding the exact time of exposure.
The following family study demonstrates an exposure to a common source, that of leaky plastic "freeze-balls." Manufactured in Hong Kong, these water-filled plastic balls (Figure) are frozen and used to cool foods and drinks without causing dilution as the ice melts. Exposure to these cooling devices resulted in a uniform incubation period with all ten family members in whom hepatitis was diagnosed on the same day. However, presenting manifestations, abnormal laboratory studies, and clinical course varied widely