A serological survey has been used to investigate the epidemiology of parvovirus B19 infection in England and Wales. A total of 2835 sera representing the complete age range were selected from a convenience collection obtained in 1996 that reflects the general population and screened for parvovirus B19-specific IgG. Antibody prevalence rose nonlinearly with age from 21% in those aged 1–4 years to >75% in adults aged ⩾45 years. Force-of-infection estimates were similar to those previously made in 1991, being highest in those aged <15 years. There was no association between evidence of previous infection and sex or region. Quantitatively strongest antibody responses were found in those aged 15–34 years and IgG levels in females were 28·5% higher than those found in males (P=0·004, 95% CI 8·2–52·6). Applying the upper 95% confidence interval for the force of infection to maternity estimates for England and Wales in 1996, parvovirus infection in pregnancy was estimated to occur on average in up to 1 in every 512 pregnancies each year. This represents 1257 maternal infections, causing up to an estimated 59 fetal deaths and 11 cases of hydrops fetalis annually. An analysis of all available laboratory-confirmed parvovirus infections found a mean of 944 infections per year in women aged 15–44 years highlighting a need for enhanced surveillance of maternal parvovirus B19 infection in England and Wales, including information on both pregnancy and outcome of pregnancy.

We have developed a microimmunofluorescence test (IF) which uses cells infected with a recombinant baculovirus which expresses the capsid proteins of astrovirus types 1 or 6. The IF test was sensitive and specific and the results for human astrovirus type 1 (HAst-1) were comparable to those obtained by immune electronmicroscopy and radioimmunoassay. Application of the test to a panel of 273 sera collected from patients and staff at two childrens hospitals in London showed that over 50% of the population were infected by Hast-1 between the age of 5 and 12 months rising to 90% by 5 years, whereas human astrovirus type 6 (HAst6) was relatively uncommon (10–30%) in all age groups.

Statistical models of epidemiology in wildlife populations usually consider diseased individuals as a single class, despite knowledge that infections progress through states of severity. Bovine tuberculosis (bTB) is a serious zoonotic disease threatening the UK livestock industry, but we have limited understanding of key epidemiological processes in its wildlife reservoirs. We estimated differential survival, force of infection and progression in disease states in a population of Eurasian badgers (Meles meles), naturally infected with bTB. Our state-dependent models overturn prevailing categorizations of badger disease states, and find novel evidence for early onset of disease-induced mortality in male but not female badgers. Males also have higher risk of infection and more rapid disease progression which, coupled with state-dependent increases in mortality, could promote sex biases in the risk of transmission to cattle. Our results reveal hidden complexities in wildlife disease epidemiology, with implications for the management of TB and other zoonotic diseases.

The COVID-19 pandemic is exerting major pressures on society, health and social care services and science. Understanding the progression and current impact of the pandemic is fundamental to planning, management and mitigation of future impact on the population. Surveillance is the core function of any public health system, and a multi-component surveillance system for COVID-19 is essential to understand the burden across the different strata of any health system and the population. Many countries and public health bodies utilise ‘syndromic surveillance’ (using real-time, often non-specific symptom/preliminary diagnosis information collected during routine healthcare provision) to supplement public health surveillance programmes. The current COVID-19 pandemic has revealed a series of unprecedented challenges to syndromic surveillance including: the impact of media reporting during early stages of the pandemic; changes in healthcare-seeking behaviour resulting from government guidance on social distancing and accessing healthcare services; and changes in clinical coding and patient management systems. These have impacted on the presentation of syndromic outputs, with changes in denominators creating challenges for the interpretation of surveillance data. Monitoring changes in healthcare utilisation is key to interpreting COVID-19 surveillance data, which can then be used to better understand the impact of the pandemic on the population. Syndromic surveillance systems have had to adapt to encompass these changes, whilst also innovating by taking opportunities to work with data providers to establish new data feeds and develop new COVID-19 indicators. These developments are supporting the current public health response to COVID-19, and will also be instrumental in the continued and future fight against the disease.

The objective was to evaluate foodborne outbreaks of undetermined aetiology by comparing them to pathogen-specific epidemiologic profiles of laboratory-confirmed foodborne outbreaks. National foodborne outbreak data reported to CDC during 1982–9 were categorized by clinico-epidemiologic profiles based on incubation, duration, percent vomiting, fever and vomiting to fever ratio. From the pathogen-specific profiles, five syndromes were developed: a vomiting-toxin syndrome resembling Bacillus cereus and Staphylococcus aureus; a diarrhoea-toxin syndrome characteristic of Clostridium perfringens, a diarrhaeogenic Escherichia coli syndrome, a Norwalk-like virus syndrome, and a salmonella like syndrome. Of 712 outbreaks, 624 (87·6%) matched one of five syndromes; 340 (47·8%) matched the Norwalk-like syndrome and 83 (11·7%) matched the salmonella-like syndrome. After combining information on known pathogens and epidemiologic profiles, only 88 (12·4%) outbreaks remained unclassified. Norwalk-like virus outbreaks appear as common as salmonella-like outbreaks. We conclude that profiling can help classify outbreaks, guide investigations and direct laboratory testing to help detect new and emerging pathogens.

Attempts were made to identify the causative organism of Lyme disease in Australia from possible tick vectors.

Ticks were collected in coastal areas of New South Wales, Australia, from localities associated with putative human infections. The ticks were dissected; a portion of the gut contents was examined for spirochaetes by microscopy, the remaining portion inoculated into culture media. The detection of spirochaetes in culture was performed using microscopy, and immunochemical and molecular (PCR) techniques. Additionally, whole ticks were tested with PCR for spirochaetes.

From 1990 to 1992, approximately 12000 ticks were processed for spirochaetes. No evidence of Borrelia burgdorferi or any other spirochaete was recovered from or detected in likely tick vectors. Some spirochaete–like objects detected in the cultures were shown to be artifacts, probably aggregates of bacterial flagellae.

There is no definitive evidence for the existence in Australia of B. burgdorferi the causative agent of true Lyme disease, or for any other tick–borne spirochaete that may be responsible for a local syndrome being reported as Lyme disease.

The natural habitat of Paracoccidioides brasiliensis, agent of paracoccidioidomycosis (PCM), remains unknown. This study is aimed at establishing associations between the ecological variables present in all Colombian municipalities and the incidence of PCM. Records of 940 patients were studied and several ecological variables analysed, as well as their association to amount of patients per total rural population in each municipality, determined through a multivariate analysis. All 940 patients came from 216 municipalities (20·3 %), out of which, 93 were birthplace and place of long-term residence for 121 patients. The Incidence Rate Ratio (IRR) was determined for these 93 municipalities. The following variables fitted the model: altitude from 1000 to 1499 metres above sea level (IRR = 6·37), rainfall from 2000 to 2999 mm (IRR = 2·15), presence of humid forests (Holdridge) (IRR = 1·79) and coffee (IRR = 1·95), tobacco (IRR = 3·59) crops. These results indicate that these municipalities constitute reservareas for P. brasiliensis (Borelli).

1. By means of the Old Standard bismuth sulphite medium B. typhosus was cultivated 44 times out of 50 examinations of the stools of 50 typhoid fever patients and convalescents.

2. By means of the same medium B. paratyphosus B was cultivated 22 times out of 27 examinations of the stools of 27 different cases of paratyphoid fever.

3. In 13 examinations of Belfast sewage in different months during 1928 and 1929, by means of the Old Standard sulphite media, B. typhosus was isolated on 10 occasions. In two examinations of Lisburn sewage B. typhosus was isolated. Although no special search for B. paratyphosus B was undertaken, this organism was isolated on two occasions from Belfast sewage. The viability of B. typhosus and B. paratyphosus B in sewage is longer than was suggested by the work of previous observers. It has been possible to cultivate B. typhosus and B. paratyphosus B from the deposit of sewage stored in a bottle at room temperature for 3 weeks. On one occasion B. typhosus was found alive at the end of 5 weeks.

4. On two occasions water from the River Lagan was examined, and on one of these B. typhosus and B. paratyphosus B were cultivated.

5. For the isolation of the B. enteritidis Gaertner the media gave good results in the examination of faeces from cases of food-poisoning.

The risk of Borrelia burgdorferi infection and the value of antibiotic prophylaxis after tick bite are controversial. In this study, performed in two areas of southwestern Germany, ticks were collected from 730 patients and examined by the polymerase chain reaction (PCR) for B. burgdorferi. To assess whether transmission of B. burgdorferi occurred, the patients were clinically and serologically examined after tick removal and during follow-up examinations. Data from all tick bites gave a total transmission rate of 2·6% (19 patients). Eighty-four ticks (11·3%) were PCR positive. Transmission occurred to 16 (26·7%) of 60 patients who were initially seronegative and could be followed up after the bite of an infected tick. These results indicate that the transmission rate from infected ticks in Europe is higher than previously assumed. Examination of ticks and antibiotic prophylaxis in the case of positivity appears to be indicated.

Isolates of capripoxvirus collected from sub-Saharan Africa were compared in sheep, goats and cattle and by restriction endonuclease digestion of their purified DNA. Biochemical techniques were used to precisely identify strains of capripoxvirus for epidemiological investigations. Strains of capripoxvirus infecting cattle have remained very stable over a 30-year period and are closely related to strains recovered from sheep in Africa.

This article describes the spatial and temporal distribution of verotoxin-producing Escherichia coli among humans (EHEC) and cattle (VTEC) in Sweden, in order to evaluate relationships between the incidence of EHEC in humans, prevalence of VTEC O157 in livestock and agricultural structure by an ecological study. The spatial patterns of the distribution of human infections were described and compared with spatial patterns of occurrence in cattle, using a Geographic Information System (GIS). The findings implicate a concentration of human infection and cattle prevalence in the southwest of Sweden. The use of probability mapping confirmed unusual patterns of infection rates. The comparison of human and cattle infection indicated a spatial and statistical association. The correlation between variables of the agricultural structure and human EHEC incidence was high, indicating a significant statistical association of cattle and farm density with human infection. The explained variation of a multiple linear regression model was 0·56.

Previous studies examining the weather–bacillary dysentery association were of a large time scale (monthly or weekly) and examined the linear relationship without checking the linearity assumption. We examined this association in Beijing at a daily scale based on the exposure-response curves using generalized additive models. Our analyses suggested that there were thresholds for effects of temperature and relative humidity, with an approximately linear effect for temperature >12·5 °C [excess risk (ER) for 1 °C increase: 1·06%, 95% confidence interval (CI) 0·63–1·49 on lag day 3] and for relative humidity >40% (ER for 1% increase: 0·18%, 95% CI 0·12–0·24 at lag day 4); and there were linear effects of rainfall (ER for 1-mm increase: 0·22%, 95% CI 0·12–0·32), negative effects for wind speed (ER: −2·91%, 95% CI −4·28 to −1·52 at lag day 3) and sunshine duration (ER: −0·25% 95% CI −0·43 to −0·07 at lag day 4). This study suggests that there are thresholds for the effects of temperature and relative humidity on bacillary dysentery, and these findings should be considered in its prevention and control programmes.

Homologous and heterologous haemagglutination-inhibition (HAI), complement- fixation (CF), immunodiffusion (ID) and mouse neutralization tests were performed with the Lunyo (LUN) and a Zimbabwean strainof Rift Valley fever (RVF) virus, the prototype and a South African strain of Arumowot (AMT) virus and prototype strains of Gordil (GOR), Saint-Floris (SAF) and Gabek Forest (GF) viruses, using immune mouseascitic fluids prepared against these viruses. Reactions of identity occurred in all tests between LUN and the Zimbabwean strains of RVF and between the two strains of AMT virus. Otherwise, cross-reactions occurred between all the phleboviruses in HAI tests, while reactions in CF, ID and neutralization testswere monospecific for virus serotypes, except that weak cross-reaction occurred between GOR and SAF viruses in CF and ID tests.

Four sheep infected subcutaneously with the Zimbabwean strain of RVF virus developed transient fever, viraemia, leucopaenia, relative thrombocytopaenia, haemoconcentration and raised serum enzyme levels, which indicated that the sheep had developed necrotic hepatitis. Disseminated focal necrotic hepatitis was confirmed in a sheep killed for examination on day 4 post-infection. The other three sheep recovered uneventfully after only mild depression and anorexia. Groups of three sheep infected with SAF, GOR, AMT and GF viruses had no demonstrable viraemia or other sign of infection or illness, except that the sheep infected with AMT developed mild fever lasting less than 24 h.

Antibody responses were monitored at intervals over a period of 24 weeks in all sheep by homologous and heterologous HAI, CF and cell culture neutralization (CPENT) tests. Homologous antibody responses were marked in the RVF-infected sheep and their sera cross-reacted strongly in HAI tests with antigens of the other viruses. The sera of the RVF-infectes sheep cross-reactes less marledly in CF and CPENT tests. Homologous antibody responses were poor in all the sheep infected with phlebovirused other than RVF, and the cross-reactivity of their sera RVF antigen or virus was negligible. All sheep were challenged with RVF virus 48 weeks after their initial infection. The sheep which had originally been infected with RVF virus were immune and developed neither fever nor viracmia. All other sheep developed fever, viraemia and antibodies to RVF virus.

It was concluded that the African phleboviruses, other than RVF, are unlikely to cause disease in livestock ot to induce antibodies which could cause confusion in the diagnosis of RVF.

A survey of the microbial quality of table eggs sold in Trinidad was conducted. For 23 poultry layer farms each visited twice approximately 1 month apart, 25 pooled eggs constituted a composite sample, for 14 shopping malls each visited twice approximately 1 month apart, six pooled eggs made a composite sample and for a total of 102 other retailers across the country each visited once over a 4-month period, six pooled eggs constituted a composite sample. Swabs of egg shells and egg content were tested for selected bacteria. Twenty-four (13·0%), 68 (37·0%), and two (1·1%) of a total of 184 composite eggs (shells, egg content or both) sampled were positive for Salmonella, Escherichia coli, and Campylobacter respectively. All 184 samples tested were negative for Listeria spp. Salmonella was recovered from seven (3·8%) egg shell samples only compared with 14 (7·6%) egg content samples only positive for the pathogen. Fifty-two (28·3%) egg shell samples and seven (3·8%) egg content samples were positive for E. coli. Both isolates of Campylobacter coli originated from egg contents. Of a total of 24 composite egg samples positive for Salmonella, eight different serotypes of Salmonella were isolated from a total of 24 Salmonella-positive composite eggs of which S. Enteritidis was the most prevalent, 58·3% (14/24). Salmonella Georgia was isolated for the first time in Trinidad. Failure to properly handle or heat table eggs sold in Trinidad poses a potential health hazard to consumers because of their poor microbial quality.

The extended phage-typing scheme described for Campylobacter jejuni and Campylobacter coli has established 46 different phage types using 19 typing phages. Altogether 754 campylobacter isolates, 672 C. jejuni and 82 C. coli, isolated from human and non-human sources received from 17 different countries were phage-typed. Overall, 80·6% of the total isolates were typable. Among typable strains, 9 phage types (3, 5, 10, 11, 18, 19, 23, 26 and 44) represented 57·0% of the strains, 21·3% of the strains belonged to another 37 phage types and the remaining 2·3% of isolates were designated atypical. The most common phage type 11 (140/754) was frequently observed among C. jejuni isolates from human (113/561) and non-human sources (18/111). whereas type 44 was frequent among C. coli isolates from human (22/59) and from non-human sources (8/23). A study of the animal host-associations of common phage types showed that contaminated cattle and poultry appear to be the most common sources of human infection. The greatest variety of phage types was observed in Canada (24 phage types), followed by Portugal (17 types) and the UK (14 types), reflecting the larger sample sizes from these countries. Phage type 11 was encountered in 12 different countries and prevalence of other phage types varied from one country to another. The number of isolates typable with the scheme varied from 93·2% (261/280) in Canada to 61% (47/77) in Thailand. However, the number and diversity of phage types makes phage typing the method of choice in epidemiological studies of campylobacter infections.

The identification of 18 strains of haemadsorbing viruses as parainfluenza type 4 viruses subtypes A and B is reported, as is a serological survey to show the distribution of antibody to these viruses in various age groups. The results suggest that although isolation of the virus is infrequent, infection in early childhood is common and the viruses may be important respiratory pathogens.

I wish to thank Dr G. B. Bruce White for kindly providing sera and also Dr B. E. Andrews, Dr Suzanne K. R. Clarke, Dr F. O. MacCallum, Dr E. M. Mackay Scollay, Dr Hélène J. Mair and Dr J. O'H. Tobin for sending the strains.

The aim of this study was to assess the change of seasonal pattern of Japanese encephalitis (JE) cases in the post-vaccination period and to elucidate whether the lagged climate variables (precipitation and temperature) were associated with occurrence of JE after adjustment for seasonal pattern, time trend, geographic areas, pig density, vaccination coverage rate for humans, and time dependence of time-series numbers of JE cases. A total of 287 confirmed JE cases between 1991 and 2005 were collected, together with monthly data on socio-ecological archival data including climate, pig density and vaccination. A time-series generalized autoregressive Poisson regression model was used to achieve the objectives. The rate of JE increased from 1998 onwards. The seasonal pattern on occurrence of JE cases clustered between May and August during the period from 1991 to 2005 in Taiwan. In each geographic area, monitoring temperature and precipitation, two possible proxy variables for mosquito density, in conjunction with seasonal factors and pig density is of assistance in forecasting JE epidemics.

1. The field epidemiology is described of two epidemics of smallpox which occurred in Tripolitania during 1946.

2. Control was effected by the ‘expanding ring’ method instead of mass vaccination of the population.

3. Five hundred cases were admitted to hospital and statistics are given of mortality in relation to age, sex and vaccination state.

4. A new clinical classification is described which enables a reliable prognosis to be made and provides a guide to treatment.

5. Controlled experiments were made on the use of penicillin in treatment. Although it is without effect on the viraemia and in general does not significantly affect mortality, it has the power of suppressing suppuration and reducing the effect of secondary sepsis. It also minimizes the amount of permanent scarring of the skin.

6. Evidence is presented to show that the period of maximum infectivity is the stage of the pre-eruptive fever. The mildest cases are infectious, but only for a short time.

The virus contained in dried scabs is not considered to be an important source of infection; it may, be modified in some way by passage through the skin.

7. Although not protected by successful vaccination many contacts showed a considerable resistance to infection. Amongst the older people this may have been due to previous clinical or subclinical attacks. Amongst the younger persons evidence is produced to show that many were relatively refractory to vaccination and experienced the disease in a different way, suggesting that there is natural partial immunity to smallpox in this particular population.

8. The complex problem of immunity in smallpox is discussed, and it is suggested that three factors operate, an anti-invasion factor, an anti-dissemination factor and a local skin immunity mechanism. A photograph is given of a model made to show the interaction of these three factors in producing the immunity levels which determine the type of disease. It also accounts for the immunity reactions in vaccinia and in smallpox in the vaccinated subject, both when vaccinated successfully during the incubation period of smallpox and when vaccinated successfully some time prior to contact.

It was perhaps unfortunate that this work had to be done under Service conditions without access to literature such as Ricketts & Byles's (1908) classic The Diagnosis of Smallpox, or Marsden's works, particularly his review of vaccination (1946). The lack of authoritative guidance, however, was compensated for by the enthusiasm of all concerned.

I am especially grateful to Lt.-Col. W. McN. Graves-Morris, R.A.M.C., P.M.O. Tripolitania, for allowing me the opportunity to experiment and to use such a large proportion of the territory's supply of penicillin.

I am indebted to Col. W. W. Sharpe, R.A.M.C., D.D.H., M.E.L.F., for enabling me to return to Tripolitania for a short time to complete the records, and to Capt. J. Macbeth, R.A.M.C., Capt. W. L. Forbes, R.A.M.C., Capt. J. Anderson, R.A.M.C. and the late Capt. J. LaFerla, R.A.M.C, who assisted at different stages and in different ways.

A multistate outbreak of Escherichia coli O157:H7 infections occurred in the USA in November–December 2006 in patrons of restaurant chain A. We identified 77 cases with chain A exposure in four states – Delaware, New Jersey, New York, and Pennsylvania. Fifty-one (66%) patients were hospitalized, and seven (9%) developed haemolytic uraemic syndrome; none died. In a matched analysis controlling for age in 31 cases and 55 controls, illness was associated with consumption of shredded iceberg lettuce [matched odds ratio (mOR) 8·0, 95% confidence interval (CI) 1·1–348·1] and shredded cheddar cheese (mOR 6·2, CI 1·7–33·7). Lettuce, an uncooked ingredient, was more commonly consumed (97% of patients) than cheddar cheese (84%) and a single source supplied all affected restaurants. A single source of cheese could not explain the regional distribution of outbreak cases. The outbreak highlights challenges in conducting rapid multistate investigations and the importance of incorporating epidemiological study results with other investigative findings.

Leptospira interrogans, hantaviruses (particularly Seoul virus), hepatitis E virus (HEV), and Toxoplasma gondii are rat-associated zoonoses that are responsible for human morbidity and mortality worldwide. This study aimed to describe the infection patterns of these four pathogens in wild rats (Rattus norvegicus) across socioeconomic levels in neighbourhoods in Lyon, France. The infection or exposure status was determined using polymerase chain reaction or serology for 178 wild rats captured in 23 locations; additionally, confirmatory culture or mouse inoculation was performed. Multivariate logistic regression analyses were used to investigate whether morphological and socioeconomic data could predict the infection status of the rats. This study revealed that the rat colony's age structure may influence the prevalence of L. interrogans, hantavirus, and HEV. In addition, areas with high human population densities and low incomes may be associated with a greater number of infected rats and an increased risk of disease transmission.