Two phenotypes of human influenza A(H1N1) virus are currently circulating in Japan. One (group 1) agglutinates both chicken and goose red blood cells (CRBC and GRBC), the other (group 2) agglutinates GRBC but not CRBC. In the 1995/6 season, group 2 viruses accounted for 70% of the H1N1 viruses isolated in MDCK cells. The 1995/6 viruses were located on two branches of the genetic tree. One branch contained both group 1 and group 2 viruses and the other branch contained only group 2 viruses. Group 2 viruses had aspartic acid at residue 225 in the haemagglutinin (HA) protein, the key amino acid residue for group 2 phenotype. The HA protein of group 1 viruses had a change from aspartic acid to asparagine at residue 225 and the expressed HA protein of these viruses adsorbed CRBC. Serial passage of group 2 viruses in MDCK cells or embryonated chicken eggs caused these viruses to gain the ability to agglutinate CRBC. MDCK-adapted viruses had the same amino acid sequences of HA polypeptide as the original ones, but egg-adapted viruses had changed amino acid sequences. The expressed HA protein from one egg-adapted virus that originally belonged to group 2 adsorbed CRBC.

In order to determine antibody levels against Streptococcus pneumoniae (pneumococcus) and Haemophilus influenzae type b (Hib) in a population of splenectomized subjects, 561 persons in a Danish county, splenectomized between 1984 and 1993 were identified. Two hundred and thirty-five were alive and 149 participated in the study. Each person donated a blood sample for antibody determination by ELISA. Though vaccine coverage among the 149 persons was 91% only 52% had ‘protective’ levels of pneumococcal antibodies. Despite recommendations for regular follow-up on pneumococcal antibody levels this had only been carried out in 4% of the subjects. Splenectomized subjects who needed pneumococcal revaccination were significantly more likely to have received their initial vaccination less than 14 days before or after splenectomy, as recommended, than those not requiring revaccination. Therefore, the timing of initial pneumococcal vaccination in relation to splenectomy seems to be important. All persons had Hib antibody levels higher than 0·15 μg/ml and 60% had levels higher than 1 μg/ml, which are the levels thought to provide short term and long term protection, respectively. In total, 37% of the 149 persons tested had pneumococcal and Hib antibody levels thought to correlate with protection from serious infections.

A retrospective study was carried out to determine the recent epidemiology of ectopic pregnancy in England between the biennial years 1988/9 and 1992/3. The number of ectopic pregnancy cases were combined with numbers of conceptions and the rates analysed for trend over time. The incidence of ectopic pregnancy rose significantly (P=0·05) over this period. However, this could be entirely explained by increasing numbers of births in older women and a highly significant positive association was found between risk of ectopic pregnancy and maternal age (P<0·0001). Over the study period the incidence of ectopic pregnancy in women aged 40 years or more was over 14 times that observed in those under 16 years of age. It is suggested that this reflects cumulative risk of acquiring pelvic inflammatory disease. The surveillance of ectopic pregnancy provides a useful indicator of the level of reproductive morbidity in women.

The effectiveness of influenza vaccination in reducing hospitalization of people with diabetes for influenza, pneumonia, or diabetic events during influenza epidemics was assessed in a case control study in Leicestershire, England. Cases were 80 patients on the Leicestershire Diabetes Register who were admitted and discharged from hospital with International Classification of Disease codes for pneumonia, bronchitis, influenza, diabetic ketoacidosis, coma and diabetes, without mention of complications, during the influenza epidemics of 1989–90 and 1993. One hundred and sixty-controls, who were not admitted to hospital during this period, were randomly selected from the Register. Immunization against influenza was assessed in 37 cases and 77 controls for whom consent was obtained to access their clinical notes and for whom notes were available. Significant association was detected between reduction in hospitalization and influenza vaccination during the period immediately preceding an epidemic. Multiple logistic regression analysis estimated that influenza vaccination reduced hospital admissions by 79% (95% CI 19–95%) during the two epidemics, after adjustment for potential confounders.

During the spring of 1993 an estimated 403000 residents of the greater Milwaukee, Wisconsin area experienced gastrointestinal illness due to infection with the parasite Cryptosporidium parvum following contamination of the city's water supply. To define the clinical, laboratory and epidemiologic features of outbreak-associated cryptosporidiosis in children, medical and laboratory records for all children submitting stool samples to the microbiology laboratory of the Children's Hospital of Wisconsin between 7 April and 13 May 1993 were reviewed retrospectively. Interviews with parents were also conducted to obtain additional clinical history. Cryptosporidium, as the sole pathogen, was identified in stools from 49 (23%) of the 209 children enrolled in the study. Children with laboratory-confirmed cryptosporidiosis were more likely to live in areas of Milwaukee supplied with contaminated water (RR=1·92, CI=1·19–3·09), to be tested later in their illness (P<0·05), to have submitted more than one stool specimen (P=0·01), to have an underlying disease that altered their immune status (RR=2·78, CI=1·60–4·84), and to be older than 1 year of age (RR=2·02, CI=1·13–3·60). Clinical illness in these patients was more prolonged and associated with weight loss and abdominal cramps compared with Cryptosporidium-negative children. In the context of this massive waterborne outbreak relatively few children had documented infection with Cryptosporidium. If many children who tested negative for the parasite were truly infected, as the epidemiologic data suggest, existing laboratory tests for Cryptosporidium were insensitive, particularly early in the course of illness.

Glycopeptide resistance in enterococci is now a cause of clinical concern in the United States and Europe. However, details of vancomycin resistance in enterococci in Japan have been unknown. We measured minimum inhibitory concentrations (MICs) of various antimicrobial agents for a total of 218 clinical strains of enterococci isolated in our hospital in 1995–6 in addition to 15 strains with known genotypic markers of resistance. We also screened vancomycin resistance genes using a single step multiplex-PCR.

In clinical isolates, only two strains of Enterococcus gallinarum were of intermediate resistance to vancomycin (MIC, 8 μg/ml), while the others were all susceptible. Glycopeptides (vancomycin and teicoplanin) and streptogramins (RP 58500 and RPR 106972) showed potent antimicrobial effects for the isolates. In addition, ampicillin was also potent for Enterococcus faecalis, while ampicillin, minocycline and gentamicin were potent for Enterococcus avium. No vanA or vanB genes were detected, while vanC1 and vanC23 genes were detected from two and four strains, respectively. Our results suggest that incidence of VRE in Japan may be estimated as still very low at this time.

The prevalence of antibody against hepatitis C virus (anti-HCV) and five hepatitis B virus markers (HBVM) was measured in 176 Chinese drug addicts, of whom 23 were AIDS patients. Of 176 drug addicts, 147 were members of ethnic minorities while 29 were Han, the majority ethnic group. The total prevalence rates of anti-HCV and HBVM were 35·8% and 50·6% respectively, significantly different (P<0·01). Anti-HCV and HBVM were together found in 22·7%. Similar prevalence rates were found among the different ethnic groups. Among the ethnic minorities, there was a significantly higher prevalence rate of anti-HCV in intravenous drug addicts (IVDA, 51·1%) than in oral drug addicts (20·3%). Furthermore, the prevalence of anti-HCV was significantly higher in needle-sharing abusers (60·4%) than in non-needle sharing ones (37·1%, P<0·05). The prevalence of HBVM was also significantly higher in needle-sharing abusers (69·8%) than in non-needle sharing ones (34·3%). Prevalence of HBsAg was significantly higher in drug abusers with AIDS (47·8%) than in IVDA only (16·1%). The anti-HCV positive rates among ethnic minority people were: for the Yi people 69·2%, the Hui 55·6%, the Bai 53·9%, the Dai 26·8% and the Wa 23·1%. No obvious difference was identified for HBVM. The prevalence rates of HCV, HBV and HCV+HBV in IVDA showed no significant difference (P>0·05) between the two regions. HIV, HCV and HBV infections may promote each other and be related to needle-sharing behaviour in drug abuse and to different subcultures and living habits.

To determine the prevalence and routes of transmission of hepatitis C virus (HCV) infection in Hafizabad, Pakistan, we collected sera in 1993 from a geographically based random sample of residents, and in 1994 identified 15 HCV-infected individuals (cases) and 67 age and sex matched uninfected individuals (controls). Initially we approached 504 households, and collected serum from a randomly selected household member in 309 (64%). Twenty persons (6·5%) had anti-HCV antibody; 31% percent had hepatitis B core antibodies, and 4·3% had hepatitis B surface antigen. In the case-control study, persons who received more therapeutic injections (categorized as averaging 1, 2–4, 5–9 or >10 injections per year in the previous 10 years) were more likely to be infected with HCV (odds ratio 0, 1·5, 2·5 and 6·9 respectively, P=0·008) compared to persons averaging 0 injections per year. Efforts to limit therapeutic injections to only those that are medically indicated and that use sterile equipment are essential in order to prevent transmission of HCV.

To characterize post-treatment clearance of young forms of Plasmodium falciparum from the blood, three differential equation models, a linear decline, a linear then logarithmic decline, and the Michaelis–Menten (MM) kinetic equation, were fitted to log-transformed serial parasite counts from 30 semi-immune patients with synchronous parasitaemias allocated one of six antimalarial drug regimens. The first two equations were solved analytically. The MM equation was solved numerically using a fifth-order Runge–Kutta method. For each equation, parasite clearance was assumed stochastic and log-transformed parasite counts were assumed to be normally distributed at each time-point. Comparisons between models were by Minimum Akaike Information Criterion Estimate. A constrained MM equation fitted the data at least as well as the other two models in 5 of 6 drug groups and also when pooled data were analysed, providing a single index which could be used in drug efficacy studies in similar situations or as part of more complex models that encompass asynchronous, complicated infections.

Many aspects of the natural history of tuberculosis are poorly understood. Though it is recognized that clinical tuberculosis may follow shortly after initial infection (‘primary’ disease), or many years thereafter through either endogenous reactivation or after reinfection, the relative importance of these mechanisms is often disputed. The issue is complicated by the fact that the risks of developing disease are age-dependent, and reflect infection risks which may change over time.

This paper estimates the age-dependent risks of developing tuberculosis using an age-structured deterministic model of the dynamics of tuberculous infection and disease in England and Wales since 1900. The work extends the classical studies of Sutherland and colleagues. The best estimates of the risks of developing ‘primary’ disease (within 5 years of initial infection) were approximately 4%, 9% and 14% for individuals infected at ages 0–10, 15 years and over 20 years respectively, and a previous infection appeared to impart little protection against (further) reinfection, but 16–41% protection against disease subsequent to reinfection for adolescents and adults. We also provide evidence that reinfection made an important contribution to tuberculous morbidity in the past, as (i) exclusion of exogenous disease from the model considerably worsened the fit to observed notification rates, and (ii) the dramatic decline in the risk of tuberculous infection from 1950 in England and Wales accelerated the decline in morbidity among all individuals, even among the older age groups with a high prevalence of tuberculous infection. We conclude that the risk of infection is the single most important factor affecting the magnitude of the tuberculous morbidity in a population, as it determines both the age pattern of initial infection (and hence the risk of developing disease) and the risk of reinfection.

An outbreak of trichinosis occurred during January 1995 in a south Lebanese village with a population of 800–1000 persons. The estimated number of persons treated for a Trichinella-like illness was 200. Sixty-three persons sought medical attention at a local infirmary: 44 of them were diagnosed as having trichinosis or suspected trichinosis according to their clinical symptoms, signs and laboratory tests. An environmental investigation indicated that the source of infection was pork obtained from a single butcher in the village and consumed uncooked, as an ingredient of ‘kubeniye’ (a local dish), during Christmas and New Year's meals. Sera of patients, suspected patients, and asymptomatic controls were tested for the presence of anti-Trichinella antibodies. Eight (89%) of the 9 tested patients were positive, 1 (11%) was negative. Among the 7 suspected patients, 2 (28·5%) were positive, 3 (42·9%) had equivocal results, and 2 (28·5%) were negative. Among the 20 asymptomatic persons, 3 (15%) were positive, 12 (60%) negative and 5 (25%) had equivocal results. Specimens from the implicated pork meat were examined by microscopy and were found to contain encysted larvae of Trichinella spiralis. This outbreak of trichinosis is one of the largest reported. Previous outbreaks in Lebanon occurred under very similar circumstances, indicating a need to control and prevent the trading of pork meat that is not under veterinary control, and to increase the awareness of the population for this problem.

Between 1980 and 1994 the virological laboratory of the Institute of Hygiene and Epidemiology was responsible for the typing of enteroviruses, isolated by other, mainly university, hospital laboratories. Altogether 3333 strains of entero non-polio (EnP) were typed. The number and the most common types of EnP virus isolations varied from year to year. Each year two to three predominant types determined the main character of the EnP associated illness seen.

The aim of this study, carried out in 1993, was to evaluate diphtheria immunity in Siena. Diphtheria antitoxin levels were measured by means of the immunoenzymatic test (ELISA) in serum samples of 602 apparently healthy subjects (239 males and 363 females) of all ages residing in Siena. According to widely used criteria, 6% of the total population were susceptible to diphtheria (antibody levels <0·01 IU/ml), 71% had basic protection (0·01–0·09 IU/ml) and 23% were fully protected ([ges ]0·1 IU/ml). The results suggested that a high proportion of young population had a protective level of immunity against diphtheria, that susceptibility increased with age and a smaller proportion of males (2·9%) than females (8·3%) were unprotected; this difference was statistically significant. Our results suggest that it may be useful to revaccinate adults with low levels of diphtheria toxoid so that the percentage that remains unprotected does not put the community at risk of an outbreak of diphtheria.

Admitted medical records, from January 1988 to December 1995, of 28 symptomatic amebic patients who lived in the east-southeast area of Tokyo were studied retrospectively, in order to find the present characteristics of symptomatic amebiasis due to Entamoeba histolytica in this area. Categorized by disease, there were 14 cases of colitis, 9 cases of liver abscess, 4 cases of colitis with liver abscess, and 1 case of liver abscess with brain abscess. Patients consisted of 26 Japanese males, 0 Japanese females, 1 non-Japanese male and 1 non-Japanese female. The mean age of colitis patients and liver abscess patients was 55·4 years old and 41·3 years old, respectively. The presumed place of contraction was Japan in 64% of the patients. Forty-eight percent of male patients indicated that they engaged in homosexual or bisexual practices, and 36% of male patients who denied such sexual practices or did not answer the question had no history of marriage. Positive rate of serum titre for Treponema pallidum hemagglutination test (TPHA) and human immunodeficiency virus antibody was 42·9% and 0%, respectively. Sixty-seven percent of TPHA-positive patients indicated that they engaged in male homosexual or bisexual practices. Zymodeme patterns of E. histolytica isolated from 4 colitis patients were XIV in 1 case and II in 3 cases. Symptomatic amebiasis in the east-southeast area of Tokyo is a disease which predominantly afflicts males, especially those in their middle age, and most patients contract the disease in Japan. The high rates of patients who engaged in male homosexual or bisexual practices and the high rates of patients with positive TPHA suggest that amebiasis is likely to be sexually transmitted disease in homosexual and bisexual men in the east-southeast area of Tokyo, and zymodeme II may be the predominant type in symptomatic amebic colitis in this area.

A total of 368 blood specimens were resampled from a serum collection containing 2914 blood samples which were collected by a random sampling in Taiwan in 1991. The plaque reduction neutralization test was applied to evaluate the neutralizing ability to two strains of Japanese encephalitis viruses, i.e. Nakayama (the present vaccine strain) and JE5 (a Taiwan isolate). The result revealed that antibodies against JE virus were present in each stratified age group. Antibody positive rates were both highest in the group older than 70 years although the lowest rates were located in different groups. In addition, the result showed that the immunogenicity potency of the antibody induced by the vaccine strain did not have a good coverage against JE5. The rate of neutralizing antibodies above the level of protective efficacy of the present vaccine was limited as low as 37·93%. Efficacy of the vaccine used at present was apparently not efficient. Consideration of a more promising vaccine may be necessary.

A simulation model was constructed to assess the relative costs and cost-effectiveness of different screening and vaccination strategies for dealing with hospital incidents of varicella exposure, compared with current policies, using data from published sources and a hospital survey. The mean number of incidents per hospital year was 3·9, and the mean annual cost of managing these incidents was £5170. Vaccination of all staff would reduce annual incidents to 2·2 at a net cost of £48900 per incident averted. Screening all staff for previous varicella, testing those who are uncertain or report no previous varicella, and vaccinating those who test negative for VZV antibodies, reduces annual incidents to 2·3 and gives net savings of £440 per incident averted. Sensitivity analyses do not greatly alter the ranking of the options. Some form of VZV vaccination strategy for health care workers may well prove a cost-effective use of health care resources.

A retrospective study of notified hepatitis B virus (HBV) infection in Edinburgh during 1975–92 identified 525 acute cases. For 343 where a probable transmission route could be determined, 215 were due to shared equipment by injection drug users (IDUs), 29 to homosexual intercourse, 25 to heterosexual or household contact with IDUs, 21 to heterosexual contact with infected non-IDU partners and 53 to various other or multiple routes. Cases were unevenly distributed geographically, particularly those among IDUs. The highest incidence within a post code district was approximately 2·5 times that for all Edinburgh. Annual cases peaked in 1984 then declined to low levels in the early 1990s. This reduction was most marked among IDUs, and may be ascribed both to changed injecting behaviour and decreased susceptibility within this group. The latter factor implies that HBV infections may be an unreliable guide to human immunodeficiency virus (HIV) infection in populations where HBV is highly prevalent.

The prevalence of hepatitis B virus markers in the adult Swedish population was investigated according to age, sex, origin and demographic stratum. Sera were collected from 3382 persons in 1990–1. The sera were selected on a statistical basis considered to be representative of the Swedish population from adults aged [les ]18 years. Two of the sera (0·06%) were found to be hepatitis B surface antigen positive. The two hepatitis B carriers were of non-Scandinavian origin as were (8·9%) of those tested. A total of 90 persons had a marker of previous, hepatitis B virus infection, i.e. antibodies against hepatitis B core antigen. Of these, 66 (2·0%) were of Scandinavian origin and 24 (18·1%) from highly endemic areas. The overall hepatitis B virus marker prevalence was 2·7%. The highest age-specific prevalence of hepatitis B markers in those of Scandinavian origin was in those born in 1939 and earlier. In this age-group, women had a significantly higher prevalence (3·6%) than males (1·9%). The lowest prevalence was found in those born in 1970 and later. No significant, age-related differences between younger or older persons, or between men and women, could be found in persons of non-Scandinavian origin. The results showed significant differences in exposure to hepatitis B virus among the indigenous population, compared with those of non-Scandinavian extraction. The results do not support the proposal to include hepatitis B vaccination in the Swedish immunization schedule.

In a survey of five villages in the Eastern Highlands of Papua New Guinea, Serpulina pilosicoli was isolated from rectal swabs from 113 of 496 individuals (22·8%). Colonization rates ranged from 22·6–30·1% in four of the villages but was only 8·6% in the other village. In comparison colonization was demonstrated in only 5 of 54 indigenous people (9·3%) and none of 76 non-indigenous people living in an urban environment in the same region. Colonization did not relate to reported occurrence of diarrhoea, age, sex, or length of time resident in a village. A second set of 94 faecal specimens was collected from 1 village 6 weeks after the first set. S. pilosicoli was isolated from 27 of 29 individuals (93·1%) who were positive on the first sampling and from 7 of 65 individuals (10·8%) who previously were negative. In this case, isolates were significantly more common in watery stools than in normal stools. The annual incidence of infection in the village was calculated as 93·6%, with an average duration of infection of 117 days. S. pilosicoli could not be isolated from any village pig (n=126) despite its confirmed presence in 17 of 50 commercial pigs (34·0%) sampled at a local piggery. Four of 76 village dogs (5·3%) and 1 of 2 village ducks were colonized with S. pilosicoli, suggesting the possibility of cross transmission between humans and animals.

This paper describes a computer model that mimics the spread of bovine viral diarrhoea virus (BVDV) infection through a closed herd. The model is able to simulate the spread of infection when a persistently infected (PI) animal is introduced into an infection-free herd, and it is used to investigate the role of persistently infected animals, seroconverting animals, loss of PI calves and duration of immunity on the level of infection within the herd. Under typical management conditions one persistently infected animal poses a real threat to a herd, and the prospect of the herd becoming infection free in a 10-year period without intervention is remote. Seroconverting animals are found to be an important source of infection in herds with few immune animals. The increased loss of PI calves is likely to restrict the numbers of PI animals in a herd, and loss of immunity is important since it increases the possibility of a PI calf being born.