Enzyme-linked immunoabsorbent assay (ELISA) was used to titrate virus-specific IgG, IgM and IgA levels in nasal secretions, lung lavage fluids and serum samples sequentially obtained from lambs experimentally infected with bovine respiratory syncytial virus (RSV). Virus-specific IgG and IgM responses were measured by the indirect double antibody sandwich ELISA using anti-bovine RSV monoclonal antibody, as capture antibody, and peroxidase-conjugated anti-sheep IgG and anti-sheep IgM. Virus-specific IgA antibodies were measured by antibody capture assay using anti-sheep IgA (α–chain specific) and anti-bovine RSV monoclonal antibodies.

Bovine RSV-specific IgM and IgA antibodies were detected in the serum samples within 6 days post-inoculation (p.i.). Virus-specific IgC antibodies appeared in serum samples 4 days later. In nasal secretions, IgA antibodies appeared 7 days p.i. but IgM antibodies were not detected until 12–16 days p.i. In serum samples, IgM titres were predominant for the first 2 weeks p.i. IgC titres becoming predominant thereafter. In nasal secretions and lung lavage fluids, IgA titres were significantly higher than IgM or IgG titres up to 21 days p.i. (0·01).

Virus surveillance of Northern Ireland recreational waters, between April 1986 and May 1989 demonstrated widespread enteroviral contamination of coastal and inland waters. In 1986, enteroviruses were detected in 4 of 46 (8·7%) water samples, collected from 6 coastal bathing waters. In 1987, 49 of 107 (45·8%) samples, from 16 coastal bathing waters, yielded enteroviruses; 33 of the enterovirus positive samples passed one or both of the coliform standards outlined by the European Economic Community (EEC) bathing water directive (76/160/EEC). Enteroviruses were also detected in 33 of 39 (84·6%) samples tested from 3 inland recreational waters.

The epidemiological, clinical and virological features of 1220 children with acute bronchiolitis admitted to the Prince of Wales Hospital, Hong Kong, from 1985 to 1988 are reported. They accounted for 6·6% of total paediatric admissions and provided a case incidence of bronchiolitis requiring admission to hospital of approximately 21 per 1000 children 0–24 months of age.

The clinical course and outcome was in general benign. The average hospital stay was 5 days and there were no deaths. Ten per cent of patients were repeatedly admitted to hospital with recurrent wheezing after discharge. Two infants developed bronchiolitis obliterans.

Respiratory syncytial virus (RSV) was shown by direct immunofluorescence, virus culture and serology to be the commonest cause of acute bronchiolitis in Hong Kong. Other aetiological agents included parainfluenza and influenza viruses, adenoviruses, and Mycoplasma pneumoniae.

In contrast to western countries, a seasonal variation of bronchiolitis was found with a peak incidence in the summer months. The significance of these observations is discussed.

There is an association between excess winter mortality and epidemics of influenza and it has been suggested that annual influenza vaccination should be offered to all over 65 years old as in the United States. This paper identifies the number of people dying from influenza in Leicestershire UK during the 1989–90 epidemic and the factors associated with a fatal outcome. The findings show that deaths attributed to influenza occur predominantly in very elderly people with underlying ill-health. The risk of influenzal death is greater in residential patients and increases substantially with the number of underlying medical conditions. The estimated death rates in vaccinated and non-vaccinated groups were not significantly different, but there were trends towards protection in both residential and non-residential groups. Influenza vaccine is not reaching the principal target groups and improved methods of influenza control are required.

Accurate incidence information is required to plan and evaluate screening programmes which have been proposed for the detection of primary toxoplasmosis and cytomegalovirus infection in pregnancy. Appropriate statistical methods are described for deriving incidence rates and their confidence intervals from three types of data: change in age-specific seroprevalence, seroconversion, and IgM studies. These methods are applied to seven published studies on toxoplasmosis and cytomegalovirus carried out in the UK. In these publications only one estimate of the infection rate per pregnancy was correctly derived, and none were accompanied by confidence intervals. Using the proposed methods, most estimates of the primary toxoplasmosis rate in these studies were between 2·5 and 5·5 per 1000 pregnancies, compared to the 2 per 1000 usually cited. Most cytomegalovirus incidence estimates were between 4 and 10 per 1000 pregnancies.

Infectious diseases establish in a population of wildlife hosts when the number of secondary infections is greater than or equal to one. To estimate whether establishment will occur requires extensive experience or a mathematical model of disease dynamics and estimates of the parameters of the disease model. The latter approach is explored here. Methods for estimating key model parameters, the transmission coefficient (β) and the basic reproductive rate (RDRS), are described using classical swine fever (hog cholera) in wild pigs as an example. The tentative results indicate that an acute infection of classical swine fever will establish in a small population of wild pigs. Data required for estimation of disease transmission rates are reviewed and sources of bias and alternative methods discussed. A comprehensive evaluation of the biases and efficiencies of the methods is needed.

We studied, for two years, the prevalence of indigenous human enteric viruses in wild oysters gathered each month from the bottom of Mikawa Bay, Aichi Prefecture, Japan. Viruses were detected periodically in 9 out of 54 oyster pools prepared by the acid or polyethylene glycol precipitation method although all these 9 pools met current national bacteriological safety standards. Since most of the serotypes of the enteric viruses detected in the oysters were identical with those of viruses isolated from sick children living in the area, it is suggested that contamination of enteric viruses in the oysters would depend on the prevalence of enteric viral infections in the local inhabitants.

Eighty-seven cases of subacute sclerosing panencephalitis (SSPE) were diagnosed from September 1988 to April 1991 in Papua New Guinea (PNG), by demonstration of high-titre measles-specific antibodies in cerebrospinal fluid (CSF). For 1990 the annual incidence of SSPE, for the study provinces, was calculated to be 56 cases per million under 20 years of age and it is expected that this figure will be higher in 1991. The mean age of presentation was 4.9 years, with a male to female ratio of 1.8:1. An elevation in the ratio of immunoglobulin G as a percentage of total protein in CSF and an increase in the CSF:serum immunoglobulin G ratio was shown in SSPE patients. The dramatic appearance and high frequency of the disease in PNG might relate to the early age of measles infection encountered in children in this country.

Ticks recovered from dogs in rural villages around Madrid (Spain) were processed to isolate rickettsiae. One sample containing mixtures of ticks and four containing eggs, in which rickettsiae had been detected by indirect immunofluorescence with a human serum highly reactive to Rickettsia conorii, were decontaminated, homogenized and inoculated onto Vero cells. Two egg samples yielded a cytopathic agent that reacted positively by immunofluorescence. One sample (14H) was successfully subcultured and identified as a member of the spotted fever group rickettsia. Tick eggs provide suitable material for isolation of rickettsia.

Antibody-capture enzyme-linked immunosorbent assays (AC-ELISA) which use enzyme-labelled antigen were developed for detection of varicella-zoster virus-(VZV) specific IgM, IgA and IgG antibody in patients with varicella or herpes zoster and in sera from healthy individuals. All 18 patients with varicella developed a VZV-IgM and a VZV-IgG response, 17 also a VZV-IgA response. In contrast, all 19 patients with herpes zoster were shown to be positive for VZV-IgA whereas only 13 of these reacted positively for VZV-IgM. A VZV-IgM response was detected in only two sera from 100 healthy individuals and an IgA response in only one. The presence of virus-specific IgA and IgG in the cerebrospinal fluid as determined by AC-ELISA was a useful indicator of VZV infection of the central nervous system.

By AC-ELISA, VZV-IgG was detected predominantly in sera from patients with acute or recent VZV infection. Only 14 sera from 100 healthy individuals were positive for VZV-IgG by AC-ELISA, whereas all were positive by an indirect ELISA. These results indicate that AC-ELISA's may be useful assays for determination for acute or recurrent VZV infection, but are not suitable for determination of past infection with this virus.

A synthetic oligodeoxynucletide of 40 nucleotides corresponding to nucleotides 33–72 of the gene coding for the viral protein VP7 of rotavirus, was used as a nucleic acid probe to develop a non-radiactive hybridization method for rotavirus detection. The probe was labelled at the 3' end with biotin-7-dATP. The sensitivity and specificity of the dot blot hybridization assay for rotavirus detection was evaluated with 303 stool specimens. The results indicate that the hybridization assay has a higher sensitivity than both PAGE and EIA. Among the rotavirus strains tested 37 different electropherotypes were found. The results suggest that rotavirus diagnosis by dot hybridization using a non-radioactive probe may become routine laboratory procedure because it is simple, highly specific and very sensitive.

Summary An hypothesis that there was an annual emergence of Rift Valley fever virus in Zambia, during or after the seasonal rains, was examined with the aid of sentinel cattle. Serum samples taken during 1974 and 1978 showed evidence of epizootic Rift Valley fever in Zambia, with more than 80% positive. A sentinel herd exposed from 1982 to 1986 showed that some Rift Valley fever occurred each year. This was usually at a low level, with 3–8% of the susceptible cattle seroconverting. In 1985–6 more than 20% of the animals seroconverted, and this greater activity was associated with vegetational changes - which could be detected by remote-sensing satellite imagery-which have also been associated with greater virus activity in Kenya.

Four ponies were each inoculated with a different serotype of African horse sickness virus (AHSV) which had been passaged through cell culture in order to achieve attenuation. Three of the ponies died suddenly after showing mild clinical signs, the fourth pony remained clinically normal and was killed at day 38. Infectious AHSV was isolated from blood samples collected at intervals from all four ponies. Positive antigen ELISA reactions were only observed with blood samples from two of the ponies on the two days preceding death. Specific AHSV antibodies were detected by ELISA in serum samples from the other two ponies although one eventually died. African horse sickness viral antigens were detected by ELISA in post-mortem tissue samples collected from all four ponies. No infectious virus could be detected in tissue samples taken post-mortem from the pony which survived African horse sickness (AHS) infection. In the event of a suspected outbreak of AHS it is recommended that sera and heparinized blood should be tested for specific antibodies and AHSV antigen respectively. When available, post-mortem tissues, including spleen, heart, lung and liver, should also be tested for AHSV antigen. Although the ELISA used for the detection of AHSV antigen is highly sensitive and specific, negative ELISA results should be confirmed by virus isolation attempts.