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Dengue fever, also known as breakbone fever, is a mosquito-borne infectious tropical disease caused by the dengue virus. Symptoms include fever, headache, muscle and joint pains, and a characteristic skin rash that is similar to measles. In a small proportion of cases, the disease develops into life-threatening dengue hemorrhagic fever, which results in bleeding, thrombocytopenia, and leakage of blood plasma, or into dengue shock syndrome, in which dangerously low blood pressure occurs. Treatment of acute dengue fever is supportive, with either oral or intravenous rehydration for mild or moderate disease and use of intravenous fluids and blood transfusion for more severe cases. Along with attempts to eliminate the mosquito vector, work is ongoing to develop a vaccine and medications targeted directly at the virus.

Small round structured viruses (SRSVs, Norwalk-like viruses, NLVs) are the most common cause of outbreaks of gastro-enteritis in hospitals and also cause outbreaks in other settings such as schools, hotels, nursing homes and cruise ships. Hospital outbreaks often lead to ward closure and major disruption in hospital activity. Outbreaks usually affect both patients and staff, sometimes with attack rates in excess of 50%. For this reason, staff shortages can be severe, particularly if several wards are involved at the same time. SRSVs may be spread by several routes: faecal-oral; vomiting/aerosols; food and water. Viruses may be introduced into the ward environment by any of these routes and then propagated by person-to-person spread. In an outbreak setting, the diagnosis can usually be made rapidly and confidently on clinical and epidemiological grounds, particularly if vomiting is a prominent symptom. By the time an SRSV outbreak has been recognized at ward level, most susceptible individuals will have been exposed to the virus and infection control efforts must prioritize the prevention of spread of infection to other clinical areas bycontainment of infected/exposed individuals (especially the prevention of patient and staff movements to other areas), hand-hygiene and effective environmental decontamination. This report of the Public Health Laboratory Service Viral Gastro-enteritis Working Group reviews the epidemiology of outbreaks of infection due to SRSVs and makes recommendations for their management in the hospital setting. The basic principles which underpin these recommendations will also be applicable to the management of some community-based institutional outbreaks.

The pathogenicity of two rotavirus variants, 4F and 4S, obtained following adaptation to cell culture of rotavirus from a diarrhoeic pig in China, was compared by serial passage in 24 gnotobiotic piglets. The rotavirus variants have markedly different growth characteristics in vitro, and their genome profiles differ only in the relative migration of genes 4. Both cell culture-grown variants replicated to an equal extent in gnotobiotic piglets and neither caused disease, although weight gain was slightly affected in piglets inoculated with the 4F variant. During five serial pig-to-pig passages, variant 4F became highly pathogenic at the fourth and fifth passages, causing severe diarrhoea and weight loss, and premature death in two animals. Piglets inoculated with rotavirus variant 4S remained healthy during all passages although weight gain was slightly affected. Mean duration and peak infectivity titres of virus shedding were similar for both variants. Thus, variant 4F, which grew slowly and produced small plaques in vitro and had the faster migrating gene 4, was pathogenic in pigs, whereas variant 4S was apathogenic.

A retrospective and prospective survey was carried out to determine the relative frequency of rotavirus serotypes infecting children with diarrhea or vomiting or both who were admitted to the Hospitals for Sick Children in London during a 6-year period from 1984 to 1990. The results were compared with data for the same period from a study in Birmingham, United Kingdom. The serotype of rotaviruses infecting 1,019 children was ascertained by enzyme immunoassay with VP7-specific monoclonal antibodies. In London, serotype G1 accounted for 60% of the cases, serotype G4 accounted for 24%, serotype G2 accounted for 11%, G3 accounted for 3%, and coinfections accounted for 2%. Considerable differences in the relative prevalence of serotypes were seen when data from London and Birmingham were compared. A major shift from serotype G1 to G4 was observed in London in the 1989 to 1990 season, and a lesser shift was seen in Birmingham. Examination of the electrophoretic profiles of 611 rotaviruses from London showed that there were at least 108 different profiles. Continuous variation occurred throughout the 6-year period, and the same electropherotype never recurred once it had disappeared from the population. None of the electrophoretic profiles were characteristic of group B or group C rotaviruses. There was no evidence that any strain of rotavirus had become endemic in either of the children's hospitals in London.

Vesikari T., Ruuska T., Delem A., Andre F. E., Beards G. M. and Flewett T. H. (Department of Clinical Sciences, University of Tampere, Tampere, Finland, and the Biological Division, Smith Kline RIT Rixensart, Belgium and WHO Collaborating Centre for Reference and Research on Human Rotaviruses, East Birmingham Hospital, Birmingham, U.K.). Efficacy of two doses of RIT 4237 bovine rotavirus vaccine for prevention of rotavirus diarrhoea. Acta Paediatr Scand 80: 173, 1991. Candidate oral bovine rotavirus vaccine RIT 4237 or placebo was given to 252 Finnish infants at birth and at 7 months of age. No vaccine-associated reactions were observed. Primary rotavirus ELISA IgM responses were detected in 36% of the infants after the first vaccination; after the second dose 68% of the vaccinees were seropositive for rotavirus ELISA IgG antibody. The infants remained in clinical follow-up over two rotavirus epidemic seasons (total 28 months). Counted from child years in follow-up the overall vaccine protection rate was 43%. The clinical severity of rotavirus episodes was assessed using numerical score 0–20. Vaccine protection rate for cases with score ≥7 was 57% and for cases with score ≥11 it was 89%. It is concluded that vaccination with bovine rotavirus vaccine at birth and at 7 months of age, with the second dose given shortly before rotavirus epidemic season, protects infants against moderately severe and severe rotavirus diarrhoea in the first 2 years of life.

A single oral dose of bovine rotavirus vaccine RIT 4237 or placebo was given to 2 groups of 5-day-old infants, born in October 1984 (n = 244) and June 1985 (n = 245), who remained in follow-up for 2.8 and 2.0 years, respectively. The vaccine had no effect on the total number of detectable episodes of rotavirus diarrhoea: there were 22 cases in the vaccinees and 24 in the placebo recipients in the October group and 18 and 16 respectively in the June group. However, vaccination decreased significantly the clinical severity of rotavirus diarrhoea, as assessed by a numerical score 0-20; this vaccine effect was much greater in the infants born in October. The mean severity scores for vaccine and placebo recipients were 4.55 and 10.75 respectively in the October group (p less than 0.0001, t-test) and 8.2 and 11.6 respectively in the June group (p = 0.010, t-test). Vaccine-induced clinical protection against rotavirus diarrhoea did not correlate well with serological response after vaccination, but showed good correlation to the presence of rotavirus antibodies before the rotavirus epidemic season. It is concluded that bovine rotavirus vaccine is more efficacious when given immediately before the rotavirus epidemic season: the vaccine effect may be amplified by exposure to wild rotaviruses during the season.

It is well established that rotaviruses of group A are the most important cause of severe diarrhoea in children. The causes of most cases of infectious diarrhoea still remain unidentified, however, and there must be other viruses to be found. 'Novel' rotaviruses have recently been discovered, mainly in animals (serogroups B and C in pigs and humans, D in birds, and one or more further groups in sheep and other mammals). Except for the group B virus which has caused widespread outbreaks of quite severe diarrhoea in adults in China (still not reported from outside China) these novel rotaviruses are rarities in the human and probably represent uncommon zoonotic infections. We speculate that the Chinese virus might have arisen by reassortment of genetic segments of animal group B viruses or perhaps by mutation, and so became infectious for man. The problem of identifying and determining the importance of small round viruses is reviewed. It seems likely that the group of small, round structured viruses, including Norwalk and the viruses of plainly calicivirus morphology, are all representatives of a whole group of enteric caliciviruses. Until they can be more easily cultivated it will be difficult to make diagnostic reagents available to all. Astroviruses and genuine parvoviruses have been found by many people in many countries. Astroviruses are probably more important as pathogens in lambs than in children or calves; parvoviruses can only be established as significant in epidemics. The coronavirus-like particles, first found in Vellore and Bristol, are still enigmatic and their role in diarrhoea is uncertain. Toroviridae, recently discovered as causes of diarrhoea in ungulates, do not seem to be at all important as causes of diarrhoea in humans. Possibly fruitful approaches to future searches are outlined: firstly to make more extensive use of immuno-electron microscopy; and secondly to try to improve existing tissue culture systems to make them more sensitive to enteric viruses.

OBJECTIVES: The long term effectiveness of combination therapy at reducing viral loads in seminal fluid and blood plasma obtained from HIV-1 infected men who had undergone previous antiretroviral therapy was assessed. METHODS: Samples of semen and blood were obtained from a cohort of 12 nucleoside reverse transcriptase inhibitor experienced men before and during 25-68 weeks of combination therapy, which included the protease inhibitor indinavir. HIV-1 RNA titres present in the cell free blood and seminal plasma samples were determined using the nucleic acid sequence based amplification (NASBA)/Nuclisens assay system. RESULTS: Viral RNA was detected in 9/12 and 7/12 baseline blood plasma and seminal plasma samples, with median viral titres of 10(4.81) and 10(4.56) per ml, respectively. By the end of the study period the detection rates of HIV RNA in the blood and seminal plasma samples were 5/12 and 2/12, respectively, with the median viral titres below the assay cut off level for both sample types. Of the nine patients who had detectable viral RNA in the baseline sample, only three cleared virus from both compartments by the end of the study. CONCLUSIONS: These data show that stable reduction of blood and seminal fluid viral titres is not achievable in a significant proportion of nucleoside reverse transcriptase inhibitor experienced men.

Age-specific patterns of rotavirus infection were investigated using a randomly selected and representative sample of sera from a suburban community of São Paulo, Brazil screened for class-specific antibodies to group A rotavirus. Age-serology of anti-rotavirus IgG showed primary infection predominant in young infants with a median age of around 18 months consistent with IgM serology suggesting highest rates of recent infection between ages 4 and 48 months. Anti-rotavirus serum IgA prevalence increased gradually with age. Paired samples from infants, collected 1 month apart, indicated high exposure rates with seroconversion occurring in several infants during the reported low transmission season. Between 5 and 10% of adults had elevated IgM levels indicative of recent infection and, potentially, of an important contribution adults may play to rotavirus transmission. Further understanding of the dynamics of rotavirus transmission within populations, at group and serotype level, would benefit the design and monitoring of future immunization programmes.

Vesicular fluid from rashes of 132 patients was tested by a multiplex PCR shown to be specific for herpes simplex virus (HSV) type 1 and 2, and varicella zoster virus (VZV) genomic DNA. The results were compared with those obtained by examination by electron microscopy and virus isolation by cell culture. The PCR did not differentiate between HSV 1 and 2. By PCR, 64 HSV infections and 53 VZV infections were identified, with presumed 100% sensitivity and specificity. Fifteen specimens tested negative by PCR, electron microscopy, and virus isolation for herpes viruses. The sensitivities of virus isolation and electron microscopy for detection of herpes simplex virus were 56% and 80%. For varicella zoster virus, the sensitivities of virus isolation and electron microscopy were 47% and 60%. These data illustrate the advantage of rapid PCR diagnosis of herpes simplex virus and varicella zoster virus in vesicle fluids.

Immune responses to human rotaviruses were investigated in sheep with a view to obtaining antibodies for passive immunotherapy of humans. Eighteen adult sheep with previous natural exposure to rotavirus serotypes G3 and G6 were immunized parenterally with purified preparations of either individual rotavirus serotypes G1, G2, G3, G4 and G8, or a mixture thereof. Two additional sheep were kept as control animals with the flock. The antibody responses were measured on serial serum samples by neutralization tests. The homotypic antibody response ranged from 100-fold (rarely) up to 100 000-fold increases in titre. Heterotypic responses against serotypes G3 and G6 were demonstrated in 7 12 and 15 18 sheep, respectively, but the increases in titre were lower than the homotypic responses, ranging from 10- to 100-fold in most cases and were 1000-fold in two sheep. Interestingly, no heterotypic response against the human rotavirus serotypes was raised after 3 months; moderate titres of cross-neutralizing antibodies for the human serotypes were only observed after a third inoculation.

Rotaviruses with genome rearrangements isolated from a chronically infected immunodeficient child (F. Hundley, M. McIntyre, B. Clark, G. Beards, D. Wood, I. Chrystie, and U. Desselberger, J. Virol 61:3365-3372, 1987) are the first recognized human isolates of serotype 10. This was shown by both a direct enzyme-linked immunosorbent assay and virus neutralization assays using serotype specific monoclonal antibodies. The serotype was confirmed by sequence analysis of the gene encoding VP7, which revealed a 96% amino acid homology to the bovine serotype 10 isolate B223.

An outbreak of rotavirus diarrhoea amongst patients on two wards in a geriatric unit was investigated using polyacrylamide gel electrophoresis (PAGE) and serotyping. There had been no contact between the patients on different wards but some interchange of staff had occurred so it was important to exclude the possibility that the rotavirus had been spread by staff. Two strains of rotavirus were shown to be present, one on each ward. Differences in the electropherotypes and serotypes were demonstrated, showing conclusively that transfer of virus between the wards had not occurred. Thus, serotyping and PAGE are of value in the investigation of rotavirus outbreaks in the hospital setting where cross-infection between wards is suspected.

Alkaline phosphatase amplification systems increase the sensitivity of enzyme-linked immunoassays (ELISAs). Here we describe a modified method by which levamisole is a component of the substrate buffer. This increases sensitivity by reducing the signal from non-specific alkaline phosphatases. The modified procedure was applied to an ‘in house’ HIV-1 p24 antigen capture assay and was shown to increase the sensitivity 4-fold as compared to the unmodified system. The performance of the modified amplification system is comparable to that of commercially available systems.

• Live attenuated oral rhesusRotaviruscandidate vaccine (strain MMU 18006 [lot RRV-1]) was evaluated for immunogenicity, safety, and clinical protection in a double-blind, placebo-controlled trial involving 200 infants aged 2 to 5 months when vaccinated. Vaccine-induced fourfold or greater rise ofRotavirusantibodies was seen in 62% of the infants. Febrile reactions of short duration on days 3 and/or 4 after vaccination occurred in 26% of the vaccine recipients. The clinical follow-up covered twoRotavirusseasons, in which serotypes 1 and 4 were prevalent. There were 16 cases of confirmedRotavirusdiarrhea in the placebo-treated group and 10 in the vaccine-treated group; from this a vaccine protection rate of 38% was derived. Clinical severity ofRotavirusdiarrhea was assessed by a score; 13 cases in the placebo-treated group and 5 in the vaccine-treated group were regarded as severe or moderately severe, giving a vaccine protection rate of 67%. The rhesusRotavirusvaccine induces partial protection against heterotypicRotavirusdisease, but the level of protection achieved with the present vaccine dose in this age group appears to be insufficient for a generalRotavirusvaccination. (AJDC.1990;144:285-289)

In the UK between January 1989 and December 1999 there were 164 279 reports to the PHLS Communicable Disease Surveillance Centre of cases of gastroenteritis caused by rotaviruses—an average of 14 934 each year. Rotaviruses were discovered in animals in the early 1960s and in …

The subgroups and serotypes of 178 strains of rotavirus isolated from diarrheic and healthy children in Bangui, Central African Republic, during a 27-month period were determined by enzyme-linked immunosorbent assay. The subgroup was determined for 152 of the viral strains, 18.4% being subgroup I and 81.6% being subgroup II. Of the 143 strains which could be serotyped, 71.3% were serotype 1, 15.4% were serotype 2, and 13.3% were serotype 3. Serotypes 1 and 3 were detected throughout the study, while serotype 2 was detected only during 8 months. No serotype exhibited any special epidemiological properties. The serotypes were found to consist of three different electrophoretypes, two long ones (A and B) and a short one (C). All subgroup I, serotype 2 strains presented short electrophoretypes. Strains with identical long electrophoretypes A were either serotype 1 or serotype 3.

The Chinese atypical (Group B) rotavirus, previously called the adult diarrhoea rotavirus (ADRV), was examined by transmission electron microscopy using either uranyl acetate or potassium phosphotungstate (PTA) as negative stains. Complete rotavirus particles were seen using uranyl acetate which were indistinguishable morphologically from typical rotaviruses. In the same preparations virus particles with differing degrees of degradation were seen after staining with PTA. This effect was not related to pH of the PTA and could be prevented by fixation of the specimen by 0.1 per cent glutaraldehyde. It is concluded that the use of PTA can give rise to falsely negative results for specimens containing this virus.

In a randomized, double-blind, placebo-controlled trial, 331 infants aged 6 to 12 months received orally, at an interval of 1 month, either two doses of live attenuated bovine rotavirus vaccine strain RIT 4237 or equivalent placebo. The vaccinations were carried out during September to November, a non-rotavirus season; only three cases of rotavirus diarrhea occurred in the study group before the vaccinations were completed. During the epidemic season from December to May, 31 patients with clinically significant rotavirus diarrhea required therapy. Five of these were among the 168 vaccine recipients, and 26 among the 160 placebo recipients (P less than 0.001), giving a vaccine protection rate of 82%. The incidence of clinically significant diarrhea from all causes was reduced by 76% in the vaccinees. As determined by an enzyme immunoassay antibody test with homologous virus antigen, seroconversion after vaccination was obtained in 53% of the initially seronegative infants. Clinical protection correlated well with seroconversion, but the vaccinees who failed to seroconvert also had less rotavirus diarrhea than the placebo recipients, suggesting that immunity may be mediated by factors other than serum EIA antibody. Seventeen of the 23 rotavirus isolates in the epidemic season that were typed were of serotype 1, two were of serotype 2, and four were of serotype 3. The protection rates against clinically significant diarrhea were 72%, 100%, and 100% for serotypes 1, 2, and 3, respectively. We conclude that epidemic infantile winter diarrhea associated with human rotaviruses can be significantly reduced by vaccination with the live attenuated RIT 4237 bovine rotavirus vaccine before the epidemic season.

Rotaviruses and non-cultivable enteric adenoviruses were purified from large volumes of faecal extracts using polyethylene glycol precipitation, centrifugation through 45% w/v sucrose and segregation by density in a caesium chloride density gradient. Yields were high and the preparations were pure enough to use in the production of type-specific antisera and in viral polypeptide analysis. Human rotavirus particles of density 1.38 g/ml were shown to be non-infectious for LLC-MK2 tissue culture cells.

Rotaviruses with genome rearrangements, isolated from a chronically infected immunodeficient child, were adapted to growth in BSC-1 cells. Preparations of viral RNA from fecal extracts showed a mixed atypical rotavirus RNA profile, which was due to the presence of at least 12 subpopulations of viruses grossly differing in genotype. Besides various forms of genome rearrangements involving segment 8-, 10-, and 11-specific sequences, reassortment in vivo was likely to have occurred during the emergence of these viruses. The protein products of viral genomes with various forms of segmental rearrangements seemed to be largely unaltered. Genome rearrangement is proposed to be a third mechanism directing the evolution of rotaviruses.

A neutralisation test using cell culture and indirect immunofluorescence was applied to isolates of rotavirus from 55 patients with gastroenteritis, in order to determine serotypes. Frequent cross-reactions were observed, but subsequent statistical analysis confirmed the existence of at least three distinct serotypes. Some results, not sufficient for analysis, suggest that at least five serotypes probably exist. It is suggested that two or more viral polypeptides might be involved in neutralisation, one of which might be common to another serotype(s). This would explain the frequent cross-reactions detected by this neutralisation test. Evidence suggesting that some strains may be hybrids is also presented.

Pleomorphic virus-like particles about 100 nm in diameter with a fringe of closely applied peplomers (7-9 nm in length) were observed by electron microscopy in the stools of 20 children and adults with gastroenteritis. In most of the samples no other viral or bacterial pathogens were detected. In form and under immune electron microscopy these virus-like particles resembled the Breda virus isolated from diarrhoeic calves. These objects may be a viral pathogen of humans.

A method is described for the serotyping of rotaviruses directly from samples of faeces. Serotype-specific monoclonal antibodies were used in a solid phase enzyme-immunoassay utilising a novel substrate system based on the de-phosphorylation of NADP, followed by cyclic colour reaction. This method is shown to be approximately 5–10 times more specific and sensitive than assays utilising a conventional substrate for alkaline phosphatase, and allowed serotypes to be ascribed to samples which could not be typed by other methods. The value of this method for rotavirus epidemiology and vaccine trials is discussed.

SUMMARYThe molecular epidemiology of rotavirus infections in Glasgow and the west of Scotland during 1981/82 and 1982/83 was investigated by electron microscopy, ELISA testing and RNA migration pattern analysis. In 1981/82, rotaviruses of both the ‘long’ and the ‘short’ electropherotype (in different variants) co-circulated from the onset throughout the winter peak of the outbreak. Approximately 80 % of the children were infected during the first year of life. No differences in incidence were found between sexes. In 1982/83 the isolated rotaviruses were almost exclusively of the ‘long’ electropherotype (in different variants) and 36% of the children were infected beyond the first year of life. Rotaviruses of the ‘long’ electropherotype serologically were of subgroup II and serotype 1 and those of the ‘short’ electropherotype of subgroup I and serotype 2.

A method is described for the serotyping and subgrouping of rotaviruses by enzyme-linked immuno-sorbent assay (ELISA). For the isolates tested “blind” under code in parallel the serotyping results obtained by ELISA and serum neutralization of fluorescent focus formation were the same. After absorption of the typing antisera with purified heterotypic rotavirus, up to 128-fold differences in titres between isolates were observed in the ELISA test. The results of serotyping and subgrouping, by ELISA, of strains previously described and characterized by the authors' and other laboratories are also given. An attempt is made to correlate the serological findings with variations between virus strains based upon patterns of genome molecular weights as revealed by polyacrylamide gel electrophoresis. The application of this ELISA technique to epidemiological studies and vaccine research is discussed.

Enzyme immunoassays were developed for the detection of Breda virus antibody and antigen. Cattle sera collected in the United Kingdom were found to have a high prevalence of antibody (55%) to Breda virus when examined in a competitive enzyme-linked immunosorbent assay. A low prevalence of antibody was found in pigs (2.2%), and no antibody was found in sheep or goat sera. No antibody to either Breda virus or Berne virus was detected in human sera collected from veterinarians and farm workers. Only 1 of 430 human fecal specimens (0.2%) contained Breda virus antigen detectable by enzyme-linked immunosorbent assay.

Minist?rio da Sa?de. Funda??o Servi?os de Sa?de P?blica. Instituto Evandro Chagas. Bel?m, PA, Brasil. Minist?rio da Sa?de. Funda??o Servi?os de Sa?de P?blica. Instituto Evandro Chagas. Bel?m, PA, Brasil. Minist?rio da Sa?de. Funda??o Servi?os de Sa?de P?blica. Instituto Evandro Chagas. Bel?m, PA, Brasil. Minist?rio da Sa?de. Funda??o Servi?os de Sa?de P?blica. Instituto Evandro Chagas. Bel?m, PA, Brasil. East Birmingham Hospital. Regional Virus Laboratory. Bordesley Green East, Birmingham, UK. East Birmingham Hospital. Regional Virus Laboratory. Bordesley Green East, Birmingham, UK. During July-August 1977, an outbreak of acute diarrhea occurred in an unusually isolated population, lhe Tiriy? Indians, who live in lhe north of Par?, Brazil, near lhe border with Surinam. Diarrhea was reported by 157 (70%) of lhe 224 Indians living in lhe village during lhe epidemic. There was one fatal case in a one year old child. Rotavirus was detected by electron microscopy in one fecal specimen collected from an acute case of diarrhea. Seroconversions were noted in 127 out of 168 (75.6%) paired serum samples tested for rotavirus antibody by counter-immunoelectrophoresis. With immunofluorescence based neutralization tests, rotavirus serotype 1 (Birmingham) was shown to be associated with lhe outbreak. The infection also boosted type 3 antibodies but this was most apparent in persons with pre-existing type 3 titers and lhe boost was not as great as with type 1. Ali age groups were affected. The proportion symptomatic was greatest in young children.

A method is described for the specific detection of antibody to individual rotavirus serotypes in sera. A competitive enzyme immunoassay (EIA) was developed in which rotavirus serotype-specific monoclonal antibodies against VP7 compete with antibodies in test sera for rotavirus serotype-specific antigen bound to a solid phase. There was an excellent correlation between serotype-specific EIA results and serotype-specific neutralization titres (r = 0.915, P = less than 0.001). The value of this method for rotavirus epidemiology and vaccine trials is discussed.

The influence of divalent cations on the stability of human rotavirus was investigated using the indirect immunofluorescence (FA) technique in LLC-MK2 cells to titrate infectivity. Rotavirus infectivity was stabilized by calcium and strontium ions in solution but not by magnesium ions. Rotavirus isolates were found to be much less stable at 37 degrees C than at + 4 degrees C or 20 degrees. A study of virus morphology at intervals during the course of the experiment and treatment with the chelating agents EDTA and EGTA suggests that loss of infectivity coincides with the removal of the outer capsid layer and that calcium may be required to maintain virus integrity.

The genome of human rotaviruses is composed of 11 segments of double stranded RNA. Analysis by polyacrylamide gel electrophoresis of the genomic RNA from a number of strains of the same serotype has demonstrated a significant polymorphism in the migration pattern. However, two strains differing from each other in serotype were found to have apparently identical RNA migration patterns. It is concluded that serotype cannot be deduced from RNA migration patterns. Degrees of polymorphism have been observed within each of three known human rotavirus serotypes.

Between 1983 and 1988, subgroups and serotypes were determined for 907 of 1,084 clinical specimens of rotaviruses collected in various countries of Europe, North and South America, Africa, and Asia. Enhanced enzyme immunoassays based on monoclonal antibodies specific for rotavirus proteins VP6 and VP7 were used. Significant differences in the prevalent serotypes were detected from year to year in the United Kingdom and Brazil and also in different countries during the same year. Throughout the study, rotavirus serotype 1 was detected most often (53.8%), followed in frequency by serotype 2 (17.8%), serotype 3 (12.1%), serotype 4 (11.1%), and serotypes other than 1 to 4 (5.1%). No individual serotype was found to predominate consistently in any one location. In the United Kingdom, rotavirus serotypes varied in prevalence in a regular but not predictable way. We suggest that a similar epidemiology might be found in other settings. Seventeen unusual strains were detected. Of these, five strains did not react with reference monoclonal antibodies specific for subgroup I and subgroup II, but they reacted with rotavirus group A-specific polyclonal and monoclonal antibodies; four strains were of subgroup II, serotype 2, and at least one had a "long" electropherotype; two strains were of subgroup I, serotype 2 with a long electropherotype; and one strain was of subgroup I, serotype 3. Five group C rotaviruses were detected.

Rotaviruses are the major cause of infantile gastroenteritis world-wide. Much antigenic diversity exists amongst them. This has important implications to diagnosis, epidemiology and vaccination strategies. The nature of this diversity is now well understood. This review outlines and discussed our current knowledge of the subject from a historical perspective.

A new commercial test for the diagnosis of rotavirus gastroenteritis was assessed. With some modifications it compared favourably with electron microscopy and immunofluorescence.

Rotaviruses were detected in 163 of 916 (17.8%) specimens collected from children under 3 years of age with gastroenteritis in Vellore, South India, between August 1983 and July 1985. Rotaviruses were detected throughout the study period, with a peak prevalence in December to February (winter) and June to August (southwest monsoon season). A total of 117 rotavirus strains were tested for subgroup, serotype, and rotavirus double-stranded RNA electrophoretic migration pattern; 24.8% of the strains were subgroup I, 69.2% were subgroup II, and 6.0% were neither subgroup I nor subgroup II. Subgroup I and II strains were circulating concurrently throughout the study. Of the 117 rotavirus strains, 32 (27.4%) were serotyped; 15 were serotype 1, 3 were serotype 2, 2 were serotype 3, and 12 were serotype 4. Three serotypes were circulating concurrently during the periods of peak rotavirus prevalence. In 100 of the 117 strains (85.4%) an RNA pattern was detected. One unusual subgroup I group A rotavirus with a long migration pattern and four atypical rotaviruses serologically related to group C were also detected.

Summary Rotavirus subgroups and serotypes were determined in 61 rotavirus-positive faecal samples obtained from children living in Belem, Brazil, followed up from birth to 3 years of age. Fifty-five (90%) of the specimens were subgrouped and the serotypes of 30 (49%) of them were determined. Subgroup II was detected in 49 (89%) of the 55 subgrouped strains. Serotype 1 was present in 15 (50%) of, the 30 serotyped samples; serotypes 2, 3 and 4 were found in 30%, 3.3% and 16.7% respectively, of these specimens. Absence of Vp7, the major outer capsid glycoprotein, did not allow serotyping in 21 (34.4%) of the 61 rotavirus-positive specimens, and an unidentifiable new serotype was found in faeces of one child. In addition, 4 samples were classified as subgroup II serotype 2 (which is very unusual). Twelve (80%) of the 15 serotype 1 (subgroup II) specimens were collected from children (5 of them asymptomatic) during their first year of life. All 9 serotype 2 (subgroups I, II, or not determined) samples were detected during the second and third years of life, 7 (77.8%) of them were related to apparent infections. The 5 serotype 4 (subgroup II) samples were obtained throughout the study period, and were associated with both symptomatic (3 cases) and asymptomatic infections. Thirteen children had more than 1 rotavirus infection. Three had 3 successive infections. In 3 cases, the initial infection (either symptomatic or asymptomatic) caused by serotype 1, was followed by a subsequent diarrhoeic episode associated with serotype 2.

Rotavirus gastro-enteritis in young Gambian children has its maximum impact on infants after the age of one month, in whom it produces short, well-defined annual winter epidemics with clinical dehydration in up to 18% of those infected. Sporadic infection was observed in neonates who were often asymptomatic, throughout one year but not in the subsequent year. In two consecutive years studied there was a major change from subgroup I, serotype 2 to subgroup II, serotypes 1 and 3. This could have contributed to the failure of children to develop protective immunity against sequential disease following an infection during infancy. If rotavirus morbidity in this community is to be notably reduced by a vaccination programme it would need to be carried out in early infancy prior to the winter season. Evaluation of a type-specific vaccine should include monitoring secular changes in rotavirus serotypes throughout subsequent epidemics.

Enzyme-linked immunosorbent assays were developed for the detection of group B rotavirus antigen and antibody. The specificities of both assays were evaluated for antigens and serum specific for rotavirus groups A to D. Serum collected in the United Kingdom from different animal species exhibited the following high prevalence of group B rotavirus-specific antibody: pigs, 97%; cattle, 71%; sheep, 91%; and goats, 91%. In human serum, a lower prevalence of group B-specific antibody was detected; serum from blood donors showed 10% prevalence, and serum from veterinarians showed 4% prevalence.

Research on plant virus vectors has shown that almost all types of organisms feeding on or parasitizing infected plants, including sucking and biting insects, mites, nematodes and chytrid fungi, can act as specific vectors. Surprisingly, however, natural vectors have not been found for some of the most infectious of the plant viruses such as tomato bushy stunt virus (TBSV) and tobacco mosaic virus (TMV). Here we report that when purified TBSV was consumed by human volunteers, it subsequently occurred in their faeces and could be detected by mechanical inoculation of faecal extracts to the leaves of an indicator plant (Chenopodium quinoa) in which the virus causes countable, discrete lesions. Thus, the virus remained stable on passage through the alimentary tract. The significance of man as a carrier, able to disseminate the virus widely within the environment, is discussed in relation to the epidemiology of the disease. To our knowledge, this is the first demonstration of an ‘alimentary-resistant’ plant virus.