Epidemiological survey and follow-up of transfusion-transmitted virus after an outbreak of enterically transmitted infection

An outbreak of enterically transmitted hepatitis occurred during 1996 among students at a vocational school. Viral fragments homologous to transfusion -transmitted virus (TTV) were detected in faeces. To elucidate the endemic status, an epidemiological survey and case follow-up after the outbreak wer e carried out. During and after the outbreak, virus carriers among staff we re, respectively, 32.1% and 31.3% in serum, and 24.6% and 18.2% in faeces. After the last outbreak, attacks were still occurring among new students wi th an incidence of 2.4% in 1997 and 2.3% in 1998. There was also a small-sc ale outbreak in 1998 with a prevalence of 17.9%. On follow-up at 6 and 18 m onths after onset, alanine aminotransferase (ALT) elevation was found in 29 .7% and 13.9% of patients. At 6 months, viral fragments were detected in se rum in 78.1% and 46.7% of patients, with and without ALT elevation, respect ively. At 18 months the corresponding figures were 55.6% and 19.2%, respect ively. At the 18-month follow-up, viral fragments were detected in faeces i n 29.6% and 19.3% of patients with and without ALT elevation. In conclusion , this disease might be transmitted from asymptomatic virus carriers. Accor ding to the laboratory data, both parenteral and non-parenteral transmissio ns are involved, and the faecal-oral route might be more important.