The spread of hepatitis A virus in connection with hepatitis cases in children's communities

Bulletin of the World Health Organization, 60 (2): 243-251 (1982) The spread of hepatitis A virus in connection with hepatitis cases in children's communities M. S. BALAYAN,1 M. D. ALEJNIC,2 S. S. SAVINSKAJA,3 A.G. ANDZAPARIDZE 3 A. A. BOKAREV,4 T. N. BYSTROVA,5 T. F. RJABIKOVA,5 N. V. IOSENKO, & T. A. NASTASENKO 6 In order to investigate the characteristics ofhepatitis A virus excretion, 372 children in semi-closed day-care centres were examined at the time of the seasonal increase in hepatitis incidence. Enzyme immunoassay and immune electron microscopy were used to detect virus in faeces. Ten communities were surveyed and, for the purposes of this paper, were divided into four groups on the basis of the observed pattern of virus excretion. The first group consisted of 4 communities with one hepatitis case in each; in this group, there was a relatively low rate of virus excretion throughout the study. The second group comprised 2 communities with one or two hepatitis cases; this group was characterized by an increase in the rate of virus excretion some time after isolation ofthepatient. In the communities ofthe third group, there were numerous hepatitis cases and a high rate ofvirus excretion during the first weeks ofobservation, followed by a significant decrease. There were no hepatitis cases in thefourth group, but some hepatitis A virus shedding was detected. The ratio of the number of cases to the number of virus carriers was 1:11.4 in thefirst two groups, and 1:3.4 in the third. Administration of normal serum immunoglobulin did not significantly affect the rate ofHAV excretion. The cause of the differences in shedding ofhepatitisA virus in the communities is unknown, but may possibly be related to the size of the immune section of the population. There have been many epidemiological studies of hepatitis A (infectious hepatitis) and the mode of spread of the agent was known even before the intro- duction of specific methods for the detection of hepatitis A virus (HAV) and anti-HAV antibody (1-5). There is evidence that hepatitis A can spread from a common source, such as water (6-11) or food (12- 15), but the usual mode of infection is by direct person-to-person transmission. Several methods of virus (or virus antigen) detection are applicable to HAV, including immune electron microscopy (IEM) (16, 17), radioimmunoassay (RIA) (18 - 20), and Head, Department of Viral Hepatitis, WHO Collaborating Centre for Reference and Research on Viral Hepatitis, Institute of Poliomyelitis and Viral Encephalitides, 142782 Moscow, USSR. 2 Head of Department, Research Institute of Epidemiology and Microbiology, Ministry of Health, Gorkij, USSR. 3 Research Worker, Institute of Poliomyelitis and Viral En- cephalitides, Moscow, USSR. 4 Research Worker and Physician, Research Institute of Epidemiology and Microbiology, Gorkij, USSR. s Research Worker, Research Institute of Epidemiology and Microbiology, Gorkij, USSR. 6 Postgraduate Student, Institute of Poliomyelitis and Viral Encephalitides, Moscow, USSR. enzyme immunoassay (EIA) (21 -23). Only the two latter methods, however, are suitable for surveys of large numbers of people. The detection of anti-HAV IgM by RIA or EIA has proved to be a reliable method for diagnosis of acute HAV infection (24-26), but is not directly applicable to the identi- fication of virus excreters. Virological examination of patients (27-30), human volunteers (31, 32), and chimpanzees (32 - 34) has shown that HAV is excreted before both the appearance of the first clinical symptoms and the increase in the blood aminotransferase level. Ex- cretion usually ends at about the time of the appear- ance of clinical symptoms of the disease, although in some cases the period of excretion may be more pro- tracted (28, 35, 36). It is reasonable to assume that subjects with asymptomatic infection, i.e., healthy virus carriers, have a similar period of excretion, but firm data on this topic are not available. The intensity of virus shedding among close contacts of patients is unknown, as are the factors that affect the process. The present study investigated the pattern of hepatitis A virus excretion among the close contacts of hepatitis patients, to try to determine the characteristics of the spread of infection. 4170 -243 M. S. BALAYAN ET AL. MATERIALS AND METHODS Study group and survey schedule The study was carried out among children aged 3 -7 years, attending semi-closed day-care centres in the city of Gorkij between September 1978 and January 1979, thus coinciding with the usual seasonal rise in hepatitis A morbidity. Altogether 372 children in 10 day-care centres were included in the survey (Table 1). During the obser- vation period, there were 24 clinical cases of hepatitis distributed among 9 of the centres. The cases were diagnosed by physicians in local paediatric wards on the basis of anamnesis, clinical examination, and bio- chemical analysis of blood samples. The blood samples were also tested for hepatitis B surface anti- gen (HBsAg) using countercurrent immunoelectro- phoresis (CIE) (37). Before the seasonal increase in hepatitis morbidity, 37 children received a prophylactic injection of 0.75 ml of standard polyvalent immunoglobulin which had a titre of anti-HAV antibody greater than 104 per ml as tested by enzyme immunoassay. A further 291 children were given 1.0 ml of immuno- globulin immediately after the first hepatitis case was registered in the centre that they attended. Only 8 children received no immunoglobulin at all. Each child suspected of having hepatitis was immediately isolated from the other children and hospitalized. The hygienic standards were similar in all the insti- tutions covered by the study. In the communities where hepatitis cases occurred, epidemiological data were carefully collected; all the children were examined 2 or 3 times by a paediatrician and two blood samples were taken for biochemical analysis (alanine aminotransferase and monophosphate aldolase levels and thymol test), as well as for HBsAg testing by means of CIE. Faecal specimens were collected from all the children under study 2-4 times during the period of survey, as shown in Table 1. The specimens were placed in cold storage for transport to the laboratory, and kept at - 20 °C until analysed. The children from the community where no hepatitis cases occurred did not undergo full examination, but one faecal specimen was taken from each child. Enzyme immunoassay (EIA) The EIA was performed as described by Mathiesen et al. (21). A 17% faecal extract containing HAV antigen (identified with reference sera collected from Table 1. Distribution of hepatitis cases and timing of collection of faecal specimens in children's day-care centres No. of children No. of Collection of given hepatitis faecal immunoglobulin cases specimens" Community Before After first No. of the hepatitis Symptomatic Asymptomatic 1 2 3 4 children season case 1A 25 14 6 1 0 6 12 19 2A 30 13 15 1 0 8 13 20 3A 20 0 20 1 0 17 22 4A 28 0 28 1 0 11 1 8 Subtotal (group A) 103 27 69 4 0 1B 21 10 10 1 0 16 17 27 28 2B 24 0 24 2 0 24 28 Subtotal (group B) 45 10 34 3 0 1C 22 0 22 3 2 7 13 2C 119 0 119 9 11 1 11 18 3C 47 0 47 5 2 2 9 Subtotal (group C) 188 0 188 1 7 1 5 1D 36 0 0 0 0 Total 372 37 291 24 15 a In days after the last hepatitis case. 244 SPREAD OF HEPATITIS A VIRUS 245 experimentally infected chimpanzees") was used as a positive control specimen. A negative control was provided by a pooled sample of 17Wo faecal extracts from 20 healthy children. Both positive and negative control specimens were tested by IEM with the refer- ence sera. The wells in a Linbro microtest plate" were filled with 100 Al of pretested convalescent serum contain- ing anti-HAV, and kept at 4 °C for 5 - 6 hours. The wells were then washed three times with 0.1 mol/ litre phosphate-buffered saline (pH 7.4) supplemen- ted with 5 ml of Tween-20 per litre, and filled with 10 ml/litre bovine serum albumin.' After overnight incubation at 4 °C and additional washing, 50-il aliquots of the specimen to be tested were added in the form of 17% faecal extract, prepared by the method of Bradley et al. (38). After a further 24 h, the specimen was washed again, and 50 M1 of pretitrated IgG prepared from a pretested convalescent serum and conjugated with horse-radish peroxidase were added to each well. The antibody-enzyme conjugation was performed according to the method of Nakane & Kawaoi (39), and the enzymatic activity of the conjugate was calibrated in a checkerboard titration with the refer- ence faecal specimens. Then 100 11 of substrate (1.0 ml of citrate-phosphate buffer, pH 5.0, plus 0.4 mg of 2-phenylenediamine, plus 0.6 pA of H202) were added, and the plates were incubated in the dark for 30-40 min at room temperature. The reaction was stopped by adding 50 pA of 2 mol/litre sulfuric acid. The optical density (OD) was measured spectrophoto- metrically at a wavelength of 492 nm. The specimens with a positive:negative (P/N) ratio greater than 2.1 were considered to be positive; the positive control specimen regularly had a P/N ratio of 9-10. Immune electron microscopy (IEM) Immune electron microscopy was carried out according to the method described by Gravelle et al. (40), using a pretested standard convalescent serum.d The preparations were examined using a JEOL 100 B electron microscope at an instrumental magnification of 50 000. At least 15 squares of a 200-mesh grid were examined in order to establish the presence of HAV particles in the specimen. The results were considered to be positive if typical clumps of HAV particles sur- rounded by antibody "halo" were found. The virus content in the preparations was not quantified. a Research Resources Branch, NIAID, National Institutes of Health, Bethesda, MD 20205, USA. " Flow Laboratories Ltd., PO Box 17, Second Avenue Industrial Estate, Irvine, Ayrshire, Scotland. Serva Feinbiochemica GmbH and Co., 6900 Heidelberg 1, Federal Republic of Germany. d Supplied by Dr J. E. Maynard, Centers for Disease Control, Phoenix, AZ, USA. RESULTS Of the 336 children attending the 9 day-care centres where hepatitis cases were recorded, 189 children (5607o) excreted HAV in their faeces. From an examination of the results, it appeared that the communities could be divided into four groups based on a combination of three criteria: the number of cases of hepatitis, the overall proportion of virus excreters, and the change in the proportion of excreters with time (Table 2). In the following section the characteristics of HAV excretion are examined in detail for each of these groups. Group A comprised four communities with one case of hepatitis in each, in which the proportion of excreters was relatively low and changed little with time. Group B consisted of two communities with one or two hepatitis cases, in which the overall proportion of excreters was higher than in group A and showed marked increase with time. Group C consisted of three communities, each with five or more cases of hepatitis, and in each of which there was a high proportion of excreters, which decreased gradually with time (Fig. 1). Finally, group D (one community) had no hepatitis cases. A 100 _ 80 _ 60- 40 - 17 20 - 20 105 89 m4 - iB 1 2 3 4 .° 100 - 80 60 51 = j l 2 31 lO0 0 61 2 3 4 C100 20 60 80- 60- 5 420-H 101 1 2 3 4 5 6 7 Weeks WHO 811128 Fig. 1. Percentage of faecal specimens containing hepatitis A virus in the three groups of communities. The abscissa indicates weeks after the first hepatitis case in the community. The figures above the columns give the number of specimens tested. M. S. BALAYAN ET AL. Table 2. Summary of results of virological examinations of healthy contacts of hepatitis patients Faecal specimen' Total 1 2 3 4 Virus Com- No. of ex- munity children EIA IEM EIA IEM EIA IEM EIA IEM EIA IEM creters" 1A 25 2/20 2/22 2/23 6/21 2/22 5/22 6/65 13/65 14/25 (10%) (9%) (9%) (29%) (9%) (23%) (9%) (20%) (56%) 2A 30 5/28 10/28 5/28 6/28 3/29 9/27 13/85 25/83 20/30 (18%) (36%) (18%) (21%) (10%) (33%) (15%) (30%) (67%) 3A 20 5/18 5/17 10/35 8/20 (28%) (29%) (29%) (40%) 4A 28 1/26 1/20 2/46 2/28 (4%) (5%) (4%) (7%) Subtotal 103 13/92 12/50 13/88 12/49 5/51 14/49 31/231 38/148 44/103 (group A) (14%) (24%) (15%) (25%) (10%) (29%) (13%) (26%) (43%) 1 B 21 1/16 3/19 5/15 1/20 2/7 2/7 8/9 6/8 16/47 12/54 14/21 (6%) (16%) (33%) (5%) (29%) (29%) (89%) (75%) (34%) (22%) (67%) 2B 24 4/13 2/19 16/22 19/20 20/35 21/39 22/24 (31%) (1 1 %) (73%) (95%) (57%) (54%) (91%) Subtotal 45 5/29 5/38 21/37 20/40 2/7 2/7 8/9 6/8 36/82 33/93 36/45 (group B) (17%) (13%) (57%) (50%) (29%) (29%) (89%) (75%) (44%) (36%) (80%) 1C 22 19/20 9/17 20/20 12/17 39/40 21/34 22/22 (95%) (52%) (100%) (71%) (97%) (62%) (100%) 2C 119 12/14 7/13 19/96 22/101 53/211 7/13 40/119 (86%) (53%) (20%) (22%) (25%) (54%) (33%) 3C 47 42/46 33/42 31/38 29/38 73/84 62/80 47/47 (91%) (79%) (82%) (76%) (87%) (78%) (100%) Subtotal 188 73/80 49/72 70/154 41/55 22/101 165/335 90/127 109/188 (group C) (91%) (68%) (46%) (75%) (22%) (49%) (71%) (58%) Total (groups 336 91/201 66/160 104/279 73/144 29/159 16/56 8/9 6/8 232/648 161/368 189/336 A, B (45%) (41%) (37%) (51%) (18%) (29%) (89%) (75%) (36%) (44%) (56%) and C) 1 D 36 4/36 5/17 4/36 5/17 5/36 (1 1 %) (29%) (1 1 %) (29%) (14%) Total 372 95/237 71/177 104/279 73/144 29/159 16/56 8/9 6/8 236/684166/385 194/372 (40%) (40%) (37%) (51%) (18%) (29%) (89%) (75%) (35%) (43%) (52%) No. positive/No. examined. Figure in parentheses gives percentage of positive samples. A child who had HAV in at least one faecal specimen as demonstrated by EIA or IEM. Characteristics ofHA V excretion Of the communities where hepatitis cases occurred, those in group A had the lowest rate of HAV excretion with 43%7o of the children, on average, excreting virus, compared with 80%o in group B and 58% in group C. The differences between all the groups are statistically significant (P < 0.05). However, there was a wide range in the proportion of HAV excreters in the indi- vidual communities: 7- 67%7o in group A, 67-91% in group B, and 33-10O%o in group C (Table 2). In group D, where no hepatitis cases were reported, a single examination demonstrated the presence of HAV in 14%7o of subjects, suggesting a low level of HAV circulation in this community. In considering the time course of HAV excretion only the results obtained by EIA were considered. There were clear differences in the dynamics of HAV excretion in the different groups. Group A was characterized by a relatively constant and low rate of HAV excretion between the first and fourth weeks after identification of a case of hepatitis (Fig. 1). In contrast, a statistically significant increase in the proportion of HAV excreters was observed in group B, from 19% in week 3 to 61%7o in week 4 (P < 0.05). Unfortunately, the observation period 246 SPREAD OF HEPATITIS A VIRUS was too short to detect any subsequent decrease in the rate of excretion. In group C, intensive virus shedding occurred 3 - 4 weeks after the appearance of the first case, after which the rate decreased gradually. Again, the period of observation was too short to record the complete elimination of the virus. Virologicalfindings in sick children Altogether, 39 cases of hepatitis were reported; there were 24 typical icteric cases of different degrees of severity and 15 mild nonicteric cases diagnosed by biochemical changes in the blood. In addition, there were two children who had HBsAg in their blood. In nearly all cases the first symptoms of liver disease ap- peared before specimens were collected. Altogether 11 children were observed in hospital conditions; 8 of these had clinically confirmed hepatitis, two had toxic hepatitis, and one had dyskinesia of the bile ducts. Table 3 shows data on HAV shedding by the 11 hospitalized patients at the time of development of clinical symptoms; of 8 patients with hepatitis, the presence of HAV in the faeces was demonstrated by EIA in 5 cases and by IEM in 2 cases. HAV excretion was seen in the second week after admission in two patients, cases no. 3 and 6, the latter excreting virus also during the first week. It is noteworthy that HAV was not found in serial faecal specimens from any of the children with unconfirmed diagnosis of hepatitis. Ratio of hepatitis patients to virus excreters From the above data, the ratio of the number of hepatitis cases to that of healthy virus excreters (HC/HVE) among the close contacts was calculated. It should be noted that this ratio is influenced by at least two factors specifically related to experimental conditions. First, there was a time delay between the onset of hepatitis and the detection of virus excretion; secondly, most of the children were given a prophy- lactic injection of immunoglobulin after the detection of a case of hepatitis in the community. The ratio HC/HVE for the individual children's communities is shown in Table 4. The average value for group A communities was 1: 11.0, with individual variation from 1:2 to 1:20. For group B communities the average value was 1:12.0 (1:11-1:14) and for group C it was 1:3.4 with a variation of 1:2-1:6.7. The average ratio for all the communities with cases of hepatitis was 1:4.8. Considering only the cases with an icteric form of the disease, the ratio of HC/HVE for group C was Table 3. Results of clinical and virological examination of hospitalized patients Days after hospitalizati3n no. - -1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19-29 HA, icteric form, mild 0 0 0 0 0 Q-| _ - .[-1 course A __ __t 2 HA, icteric form, moderately - * 0 0-02 severe A@AO 3 HA, icteric form, mild v * 0 o0 _ Oo-o course A_A_ AO0 HA, nonicteric form, mild - 00 0 0 04 course A I0 A___ HA, nonicteric form, mild - 0 ot L6 HA, nonicteric form, mild a* - a 0°-i| -6 course A AO 0 AO HA, nonicteric form, mild 0 0 0 0 0 07 course AO 0 1 -- AO HA, nonicteric form, mild 0 0 8 course AO _ -A - 9 HA not confirmed 0 0 0 0 10 HA not confirmed AO o0 0 0 o T Antcn 11 |HA not confirmed 0 0 C 0_ 0 0 <_- * Positive EIA (P/N>,2.1) Positive IEM Hepatomegaly * Enzyme elevation 0 Negative EIA (P/N<2.1) 0 Negative IEM A Normal liver 0 Normal enzyme levels WHO 811127 r2Ce I~~~~~~~~~~~~~~~~~~~~~~ 247 I M. S. BALAYAN Er AL. Table 4. Ratio of hepatitis A cases to healthy virus excreters in the children's communities No. of No. of No. of healthy hepatitis icteric virus excreters cases cases Community (HVE) (HC) (IC) HC: HVE IC: HVE 1A 14 1 1 1:14 1 :14 2A 20 1 1 1:20 1 :20 3A 8 1 1 1:8 1:8 4A 2 1 1 1:2 1:2 Subtotal (group A) 44 4 4 1 :11.0 1 :11.0 1B 14 1 1 1 14 1 :14 2B 22 2 2 1: 11.0 1: 11.0 Subtotal (group B) 36 3 3 1: 12.0 1: 12.0 Subtotal (groups A and B) 80 7 7 1: 11.4 1: 11.4 1C 22 5 3 1:4.4 1:7.3 2C 40 20 9 1:2.0 1:4.4 3C 47 7 5 1:6.7 1:9.4 Subtotal (group C) 109 32 17 1: 3.4 1 :6.4 Total 189 39 24 1: 4.8 1 :7.9 1:6.4 and the average for all the groups was 1:7.9. The differences in HC/HVE ratios between groups A and B combined and group C were statistically significant, both for clinically overt cases (1:11.4 versus 1:6.4, P < 0.1) and all forms of hepatitis (1:11.4 versus 1:3.4, P < 0.05). The effect of immunoglobulin administration The effect of immunoglobulin administration was studied in three communities- IA, 2A, and IB- comprising a total of 76 children. Of these, 37 children had been given a prophylactic dose before the seasonal rise in hepatitis morbidity, 31 received an Table 5. The effect of immunoglobulin administration on the rate and duration of virus excretion in children Virus HAV found excreters in faeces Immuno- No. of 3 or globulin children No. % once twice more given examined times Before the season 37 25 68 15 7 3 After hepatitis case 31 19 61 10 8 1 None 8 3 38 1 2 - injection after the occurrence of disease in their com- munity, and 8 children received no immunoglobulin at all. The rate and duration of HAV excretion were compared in these children (Table 5). The rate of HAV excretion was not influenced by the timing of immunoglobulin administration: children who received the preparation before the season of increased hepatitis incidence became virus excreters as frequently as did the children immunized after the occurrence of hepatitis cases. There was also no difference in the duration of HAV excretion. The group of children who received no immunoglobulin was too small for valid comparison. DISCUSSION This study attempted to analyse HAV shedding in children's communities, by detecting virus antigen or virus particles in faecal specimens. In general, the results obtained support the concept that virus shedding in the immediate environment of a hepatitis patient leads to infection of a considerable number of the patient's contacts (41, 42). The children's communities were divided into 4 groups on the basis of the characteristics of HAV shedding and the number of hepatitis cases occurring before specimen collection. The intensive excretion of the virus observed in groups B and C could not be attributed to differences in hygienic standards since 248 SPREAD OF HEPATITIS A VIRUS all the institutions were very similar in this respect. The most probable reason for the differences observed was a higher proportion of immune children in groups A and D communities, but information con- firming this could not be obtained. HAV shedding among nonimmune children in group B and C communities was quite high. Viro- logical data on this subject are not available in the literature, but Vernon et al. (43) found that in a comparable epidemiological situation (i.e., long-term contact of susceptible individuals with the source of infection) the hepatitis morbidity rate reached 25Wo. The intensity of virus excretion in these circumstances should be close to that observed in the present study. A high infection rate in household foci was also observed by Frosner et al. (44), exceeding 60%7o in the age group under 20 years; 52%7o of seronegative family contacts experienced the infection during one outbreak of hepatitis. Serological examination of contacts demonstrated that two-thirds of the susceptibles, mostly children, acquired antibody to HAV as a result of asymptomatic infection (45). The presence of HAV in faeces of the contacts was not determined in these studies. In the present study, the virus was detected in members of the communities over quite a long period; the extrapolated results suggest that the communities would become free of HAV some time after the seventh week following the onset of the index case. Since the period of active virus excretion in man (27, 31, 36, 40) and chimpanzee (33, 34, 46) usually lasts for 20-25 days, it is probable that in the present study secondary or tertiary involvement occurred in group A and B communities, rather than infection from one common source. In group C communities the time interval between the first and last cases of the disease varied from 13 to 26 days, so that simul- taneous infection of most of the children is conceiv- able. However, the subsequent virus excretion continued for at least a further 7 weeks. In group A and B communities there was no decrease in the rate of excretion up to the 4th week. On the basis of an analysis of epidemiologically associated cases of hepatitis A, Racela & Mosley (36) concluded that the interval between the first and the last case may be as long as 9 weeks. These data corroborate the present virological findings. Several previous studies have shown that standard polyvalent immunoglobulin reliably prevents the development of the clinical symptoms of hepatitis (47-50). Some protective effect was observed in the present study; administration of immunoglobulin to contacts after the occurrence of a hepatitis case appeared to inhibit the development of clinically manifest disease, as has been observed elsewhere (51, 52). However, the administration of immunoglobulin apparently cannot prevent virus excretion since some children given post-exposure immunoglobulin prophylaxis showed a high rate of HAV excretion. There was no difference in the rate or duration of HAV shedding in children given pre- or post-exposure immunoglobulin prophylaxis. The data obtained in the study were used to calcu- late the ratio of patients to healthy virus carriers among their close contacts. It was found that in group A and B communities, there were 11.4 carriers per patient and in group C communities (taking into account both icteric and nonicteric forms of hepatitis) there were 3.4 virus carriers per patient, the ratio for all the groups being 1:4.8. Previously, Frosner et al. (53) found the ratio of clinical forms to infection to be 1:10. A rate of hepatitis cases of 17% (54) or even more (55) of the total number of close contacts is not uncommon. It should be noted that the data in the present study were obtained by means of tests for the detection of virus antigen (EIA, RIA) or morphologically intact virus particles (IEM). None of the methods employed could quantify the level of infectious virus in excreta of hepatitis patients or healthy virus carriers. The relationship between the concentration of HAV par- ticles and infectivity of the material has not yet been established, although it has been suggested that experimental infection in humans is a more sensitive index of HAV excretion than is IEM (36). Thus, the intensive virus shedding detected by EIA and IEM in the children's communities may be considered only as a marker of hepatitis infection, and the epidemio- logical significance of the findings cannot be evaluated. It is possible that the relatively low inci- dence of hepatitis cases in the presence of a large number of virus excreters is due to the presence of pre- dominantly noninfectious virus or subviral compo- nents in the children's faeces. This possibility is supported by the results of a follow-up study on 76 families of the children found to be HAV carriers in which no case of hepatitis was recorded during the period of the present survey or the subsequent 10 months (unpublished data). In contrast, Storch et al. (56) observed a regular transmission of hepatitis A infection from children's institutions into families. 249 M. S. BALAYAN ET AL. ACKNOWLEDGEMENTS The authors are greatly indebted to Professor S. G. Drozdov, Director of the Institute of Poliomyelitis and Virus Encephalitides, and Professor 1. N. Blohina, Director of Gorkij Institute of Epidemiology and Microbiology, for their supervision and help with the study. We also thank the personnel of the Clinical Department of the Gorkij Institute of Epidemiology and Microbiology (Dr V. P. Volgin, Dr A. S. Trofimova, Dr T. V. Seveleva, Dr A. 1. Enjutina, and Dr T. K. Bockareva) for the clinical and laboratory examination of hepatitis patients; Dr R. S. Altman for assistance in collection and analysis of epidemiological data; Dr E. A. Grinstein and Dr G. A. Shirman for advice; E. V. Flotskaja, R. N. Rogovaja, E. 1. Vakar (Institute of Poliomyelitis and Virus Encephalitides, Moscow) and E. T. Levakina and N. L. Jaskelajnen (Gorkij Institute of Epidemiology and Microbiology) for technical assistance; B. 1. Kaplan who translated the paper into English; and V. A. Gorbackova for assistance in the preparation of the manuscript. RESUME PROPAGATION DU VIRUS DE L'HEPATITE A EN LIAISON AVEC DES CAS D'HEPATITE DANS DES COMMUNAUTES D'ENFANTS Le but de l'tude etait de determiner le niveau d'excretion du virus de l'hepatite A chez les enfants ayant et en contact etroit avec des cas d'hepatite. Au total, 372 enfants de 3 A 7 ans frequentant regulierement des garderies ont et exami- nes A l'epoque oui se produit une augmentation saisonniere de l'incidence de l'hepatite. Chaque fois qu'un cas d'hepa- tite s'est declare dans l'une de ces communautes, des series d'echantillons fecaux ont e prelevees chez les contacts du malade pour la mise en evidence du virus. Le virus de l'hepa- tite A (HAV) ou antigene HAV a et detecte par titrage immuno-enzymatique ou immunomicroscopie electro- nique. Une premiere analyse des resultats obtenus a montre que les communautes etudiees pourraient etre reparties en quatre groupes suivant le nombre des cas d'hepatite et les caracteristiques de la propagation de l'HAV dans chacune d'entre elles. On a rattache au groupe A quatre communautes ayant signale chacune un cas d'hepatite. Au total, le virus a et detecte dans 1307o des echantillons par titrage immuno- enzymatique, dans 2607o des echantillons par immuno- microscopie electronique, et 43%o des enfants presentaient le virus de l'hepatite dans au moins un echantillon. Dans les deux communautes du groupe B, ou avaient e denombres un ou deux cas, ces parametres etaient respectivement de 44%, 36% et 8007o. Dans le groupe C, compose de trois communautes ou avaient e enregistres cinq cas d'hepatite ou plus, des resul- tats positifs ont et obtenus pour 49°0o des echantillons par titrage immuno-enzymatique et 71%0 par immunomicros- copie electronique; d'autre part, 58% des enfants etaient porteurs de virus. Les differences observees entre les groupes pour ce qui concerne la proportion de porteurs de virus etaient statistiquement significatives. Dans le groupe D, ou a et classee une communaute n'ayant signale aucun cas d'hepatite, le niveau de propagation de l'HAV s'est revel etre faible, proche du niveau observe pour le groupe A. Des differences ont egalement et observees entre les groupes A, B et C pour ce qui concerne la chronologie de l'excretion du virus. Dans le groupe A, le taux d'excretion de l'HAV est reste relativement faible pendant toute la dur6e des observations. Le groupe B s'est caracterise par un accroissement du taux d'excretion (de 1907 a 61 070) entre les troisieme et quatrieme semaines consecutives A l'apparition du premier cas clinique. Dans le groupe C, le taux de detec- tion a e maximal (95%0) au cours de la troisieme semaine consecutive au premier cas d'hepatite et il est reste eleve jusqu'A la quatrieme semaine pour baisser ensuite graduelle- ment. La relation entre le nombre des cas d'hepatite et le niveau d'excretion du virus a e etudiee dans des commu- nautes distinctes. Les facteurs influencant l'intensite et le schema de 1'excretion de l'HAV dans differentes commu- nautes sont neanmoins restes obscurs. Peut-&re sont-ils fonction de la proportion de sujets immunises dans les communautes etudiees. Parmi les enfants ayant contracte une maladie du foie au cours de la periode ayant precede l'etude, 11 ont et observes A l'h6pital. Le diagnostic d'hepatite a et confirme pour 8 d'entre eux mais non confirme pour 3 malades. L'examen de series d'echantillons fecaux a permis de mettre en evidence l'HAV chez 5 des 8 enfants pour lesquels avait et confirme le diagnostic d'hepatite A. Quant aux trois enfants chez lesquels le diagnostic n'avait pas et confirme, 1'examen pour chacun d'entre eux de quatre A six echantillons preleves dans le courant de la premiere semaine n'a pas permis de detecter l'HAV. Le rapport entre le nombre de cas et le nombre de porteurs de virus parmi les contacts etait de 1 pour 4,8 pour l'en- semble des communautes etudiees; on notera la difference sensible observee entre les groupes A + B et le groupe C, soit respectivement 1 pour 11,4 et 1 pour 3,4. L'administration d'immunoglobuline serique normale apres l'apparition des cas d'hepatite a semble-t-il eu un cer- tain effet protecteur. 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