The conditions for a sensitive and specific solid-phase radioimmunoassay (RIA) for the detection of IgM antibodies to hepatitis A virus (HAV) were optimized, and the RIA was used to assay sera from patients with hepatitis. IgM antibodies to HAV reached highest concentrations between one and three weeks after onset of icterus and were measurable in follow-up sera for at least 12 months after infection. To prove the specificity, the IgG antibodies were separated from patient sera by sucrose density-gradient centrifugation. The remaining IgM antibodies, after treatment with beta-mercaptoethanol, did not bind in the RIA, and, when the anti-IgM antibody bound to the solid phase was replaced with anti-IgG, a negative result was obtained with incubation of IgM antibody to HAV. Also, the presence of IgG was shown not to interfere with measurement of IgM antibody to HAV. Finally, as a further specificity control, 50 sera positive for rheumatoid factor or from patients infected with hepatitis B virus, cytomegalic inclusion disease, infectious mononucleosis, influenza A virus, rubella, or measles were tested, and all of these sera were negative for IgM antibody to HAV.

SUMMARYThe suitability of serological surveys of roe deer (Capreolus capreolus) in determining the spread of tick-borne encephalitis virus (TBEV) was tested in a south German area with a low risk of TBEV infection to humans. Sera obtained from 192 hunted roe were screened by an haemagglutination-inhibition test (HAI) and in an ELISA developed in our laboratory. Those found positive were tested in a neutralization test (NT). Fifty (26-0%) sera reacted positive by ELISA and 43 (86-0%) of these were confirmed by HAI or NT. Forty-seven (24-5 %) samples were positive by HAI, 44 (93-6 %) of which were also positive in NT or ELISA. Only insignificant increase of the antibody prevalence with age (P = 0 17 for HAI antibodies) suggests that most infections occur at an early age in scattered natural foci. The antibody prevalence in females was lower than in males (OR = 0-63; P = 0-02 for HAI antibodies). In determining the distribution of seropositive roe we increased the sample size to 235 sera. No antibodies were detected in 56 (23-8 %) sera collected in the eastern third of the county. The areas of high antibody prevalence in roe match those in which humans have been infected. We conclude that serosurveys of roe deer are useful in marking out areas in which humans face the risk of infection, provided that an adequate number of sera, preferably from males, is available.

Serial blood and faecal samples were collected from patients and family contacts during an outbreak of hepatitis A in a village and tested by a solid-phase competitive type radioimmunoassay for hepatitis A antigen and hepatitis A antibody. The amount and duration of excretion of hepatitis A antigen was correlated with the severity of the illness. In 2 severe clinical cases, hepatitis A antigen was demonstrated in faecal extracts 11 days before the onset of jaundice and continuing for 10 days thereafter, with maximum shedding during the late incubation period. Faecal antigen was demonstrated in low concentrations for only 2 days in a patient with mild disease and in a person with subclinical infection. There was an inverse correlation between the incidence of infection and prevalence of hepatitis A antibody and age. Of 24 infections, 19 (79%) occurred in persons in the age group 0 to 20 years, a group in which only 6% of individuals had pre-existing antibody. Hepatitis A antibody was present in the serum of 3 persons in low titres of 1:20 to 1:40 on the day jaundice developed. The antibody titres increased very rapidly during the following 2 weeks of illness and slowly during the following months, reaching titres of 1:900 to 1:3500. In a separate study, a mean antibody titre of 1:591 was found in 13 patients, 12 years after clinical hepatitis A with jaundice.

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We developed a direct enzyme immunoassay [EIA; Enzygnost Influenza A(Ag) and Enzygnost Influenza B(Ag)] for the direct detection of influenza A and B virus antigens in nasopharyngeal secretion specimens (NPS). The test is performed without sonification of specimens, and results are obtained within 4 h. A direct comparison between direct EIA and quantitation of virus shedding for influenza A and B virus antigen detection was carried out. A total of 210 NPS and 98 nasopharyngeal wash specimens (NPW) were investigated. We isolated influenza A viruses from 79 (37.6%) of 210 NPS; of these 79 cell-culture-positive NPS, 70 (88.6%o) were also positive by direct EIA. Of 29 (13.8%) NPS from which influenza B virus was isolated, 24 (82.8%) NPS were positive by direct EIA. Virus shedding was determined quantitatively in 48 NPS from patients with influenza A and in 24 NPS from patients with influenza B. Only a crude correlation between optical density values and virus concentrations was observed. Detection of influenza virus antigens in NPS by direct EIA showed sensitivities of 89.7% for influenza A virus and 87.9%o for influenza B virus and specificities of 99.3% for influenza A virus and 100% for influenza B virus. With direct ETA, all NPW were negative for influenza A virus, although virus was isolated from 21 (21.4%) NPW. Of 15 NPW from which influenza B virus was isolated, 7 showed positive results in direct EIA. In addition, direct EIA is suitable for detecting influenza A and B viruses in cell cultures before the appearance of any cytopathic effects and can be used as a cell culture confirmation test.