A catalogue of dates and places of major outbreaks of epidemic diseases, that occurred in the Chinese Empire between 243 b.c.e. and 1911 c.e., combined with corresponding demographic data, provides a unique opportunity to explore how the pressure of epidemics grew in an agrarian society over 2000 years. This quantitative analysis reveals that: (1) the frequency of outbreaks increased slowly before the 12th century and rapidly thereafter, until 1872; (2) in the first millennium of our era, the people of China lived for decades free of major epidemics; in the second millennium, major outbreaks occurred every couple of years, but were localized; (3) in the more recent centuries, these outbreaks were as common, but disseminated to more places. This evolution, closely matching the demographic growth, was similar in the north and south of China, and therefore may have been similar in other regions of the world.

Proposed measures to contain pandemic influenza include school closure, although the effectiveness of this has not been investigated. We examined the effect of a nationwide elementary school strike in Israel in 2000 on the incidence of influenza-like illness. In this historical observational study of 1·7 million members of a preferred provider organization, we analysed diagnoses from primary-care visits during the winter months in 1998–2002. We calculated the weekly ratio of influenza-like diagnoses to non-respiratory diagnoses, and fitted regression models for school-aged children, children's household members, and all other individuals aged >12 years. For each population the steepest drop in the ratio of influenza-like diagnoses to non-respiratory diagnoses occurred in the strike year 2 weeks after the start of the strike. The changes in the weekly ratio of influenza-like diagnoses to non-respiratory diagnoses were statistically significant (P=0·0074) for school children for the strike year compared to other years. A smaller decrease was also seen for the adults with no school-aged children in 1999 (P=0·037). The Chanukah holiday had a negative impact on the ratio for school-aged children in 1998, 1999 and 2001 (P=0·008, 0·006 and 0·045, respectively) and was statistically significant for both adult groups in 1999 and for adults with no school-aged children in 2001. School closure should be considered part of the containment strategy in an influenza pandemic.

Although spatio-temporal patterns of influenza spread often suggest that environmental factors play a role, their effect on the geographical variation in the timing of annual epidemics has not been assessed. We examined the effect of solar radiation, dew point, temperature and geographical position on the city-specific timing of epidemics in the USA. Using paediatric in-patient data from hospitals in 35 cities for each influenza season in the study period 2000–2005, we determined ‘epidemic timing’ by identifying the week of peak influenza activity. For each city we calculated averages of daily climate measurements for 1 October to 31 December. Bayesian hierarchical models were used to assess the strength of association between each variable and epidemic timing. Of the climate variables only solar radiation was significantly related to epidemic timing (95% CI −0·027 to −0·0032). Future studies may elucidate biological mechanisms intrinsically linked to solar radiation that contribute to epidemic timing in temperate regions.

To gain insight into pertussis disease dynamics, we studied age-specific long-term periodicity and seasonality of pertussis in The Netherlands. Hierarchical time-series models were used to analyse the monthly reported pertussis incidence in January 1996–June 2006 by age group. The incidence of pertussis showed a slightly increasing long-term trend with highest incidence rates seen in 1996, 1999, 2001 and 2004. For all age groups the annual peak incidence was found in August, except for the 13–18 years age group where the peak occurred in November. Monthly trends in adults showed high correlation with trends in age groups 0–4 years (0·94) and 5–12 years (0·92). We found no evidence for a relationship between annual rises in pertussis and the opening of schools. Concurrent annual fluctuations of pertussis incidence in adults and infants suggest frequent transmission within and between these age groups. Studying trends offers insight into transmission dynamics and may facilitate decisions on future vaccination strategies.

Vitamin D has been shown to be an important immune system regulator. Vitamin D insufficiency during winter may cause increased susceptibility to upper respiratory tract infections (URIs). To determine whether vitamin D supplementation during the winter season prevents or decreases URI symptoms, 162 adults were randomized to receive 50 μg vitamin D3 (2000 IU) daily or matching placebo for 12 weeks. A bi-weekly questionnaire was used to record the incidence and severity of URI symptoms. There was no difference in the incidence of URIs between the vitamin D and placebo groups (48 URIs vs. 50 URIs, respectively, P=0·57). There was no difference in the duration or severity of URI symptoms between the vitamin D and placebo groups [5·4±4·8 days vs. 5·3±3·1 days, respectively, P=0·86 (95% CI for the difference in duration −1·8 to 2·1)]. The mean 25-hydroxyvitamin D level at baseline was similar in both groups (64·3±25·4 nmol/l in the vitamin D group; 63·0±25·8 nmol/l in the placebo group; n.s.). After 12 weeks, 25-hydroxyvitamin D levels increased significantly to 88·5±23·2 nmol/l in the vitamin D group, whereas there was no change in vitamin D levels in the placebo group. There was no benefit of vitamin D3 supplementation in decreasing the incidence or severity of symptomatic URIs during winter. Further studies are needed to determine the role of vitamin D in infection.

In developing countries, vaccination against highly pathogenic avian influenza subtype H5N1 (HPAI) in free-range poultry flocks is usually implemented as periodic campaigns and newborn chicks are generally not vaccinated by farmers between vaccination passes. The demographic population turnover leads to a continuous decrease in the population immunity rate (PIR) over time. We present a simple Leslie matrix model for estimating population turnover and PIR dynamics in a hypothetical small-size vaccinated free-range poultry population. Four different vaccination scenarios were identified assuming necessary procedures to achieve immunity. The results indicate that high levels of population immunity are difficult to sustain. Assuming an animal immunity response of 80% after vaccination and a constant population size, PIR 4 months after vaccination was ⩽30% in all the scenarios. Predictions averaged over time showed mean PIR between 36% and 48%, which is below the population immunity thresholds for eradication approximated from R0 estimates.

The characteristics of 359 group A streptococcal (GAS) isolates collected from Chinese paediatric patients in two periods (1993–1994, 2005–2006) were studied. Isolates were assigned to emm types and assayed for eight superantigen (SAg) genes (speA, speC, speH, speI, speG, speJ, ssa, SMEZ). Types emm1 and emm12 were consistently the most prevalent during the two periods, while others varied in frequency. GAS isolates carrying six or more SAg genes increased from 46·53% (1993–1994) to 78·39% (2005–2006); ssa, speH and speJ genes (P<0·05) increased but speA declined (P<0·05). SAg gene profiles were closely associated with the emm type, but strains of the same emm type sometimes carried different SAg genes in the two periods. No significant difference in emm-type distribution and SAg gene profile was noted between isolates from different diseases. These data may contribute towards the development of a GAS vaccine in China.

Streptococcus agalactiae is a genetically diverse organism; when typed by pulsed-field gel electrophoresis (PFGE), multiple types appear within a single serotype. We tested whether S. agalactiae PFGE types correspond to a specific serotype within individuals, and different individuals from the same geographic area. A total of 872 S. agalactiae isolates from 152 healthy individuals were classified by PFGE and capsular serotype. Serotype V was the most homogeneous (Simpson's diversity index 0·54); and types III, II and Ib were mostly heterogeneous (Simpson's diversity index ⩾0·90). Within an individual, isolates with the same PFGE patterns had identical capsular types, but across individuals the same PFGE types sometimes occurred in different serotypes. Capsular type alone is insufficient to define epidemiological relatedness. Although PFGE types appear to be a valid surrogate for capsular typing of isolates from the same individual, it is not a valid surrogate for serotype in isolates from different individuals.

A cluster of five cases of tuberculosis (TB) in persons aged 19–23 years who were not close contacts was detected in a small village in Spain in 2006. All culture isolates had the same chromosomal-DNA restriction pattern. Contact investigations of family members, friends, workmates and schoolmates were complemented with tuberculin screening offered to the resident population born between 1976 and 1995. Expanded contact tracing detected two new cases of TB, 27 tuberculin conversions and an excess of latent tuberculosis infections (LTI) in persons born between 1978 and 1990. The contacts of two cases had a significantly elevated prevalence of LTI. Two secondary cases of TB, 33·3% of those diagnosed with LTI and 47·8% of the converters were unaware of any contact with the TB cases, but had frequented some of the same bars. This study suggests that a considerable percentage of the episodes of TB transmission in young people may escape detection in conventional contact studies.

Brucellosis is an important zoonosis in Middle Eastern countries. In this study we assessed the extent of the application of planned official brucellosis control programmes in Kafr El Sheikh governorate, Egypt and we used a stochastic simulation model to assess the probable impact of changes to the official control strategy on the dynamics of small-ruminant brucellosis. Our results show that <7% of female livestock were tested in any given year in the study area and that quarantine was not consistently applied to infected herds. Simulation results revealed the inability of the applied control measures to reduce the prevalence of small-ruminant brucellosis. Given our assumptions, the intensity with which infected animals are removed under the actual levels of implementation of test-and-slaughter programmes would permit brucellosis to remain endemic at a level >8% of the sheep and goat population.

A large outbreak of Salmonella enterica serotype Newport infection occurred in Northern Ireland during September and October 2004. Typing of isolates from patients confirmed that this strain was indistinguishable from that in concurrent outbreaks in regions of England, in Scotland and in the Isle of Man. A total of 130 cases were distributed unequally across local government district areas in Northern Ireland. The epidemic curve suggested a continued exposure over about 4 weeks. A matched case-control study of 23 cases and 39 controls found a statistically significant association with a history of having eaten lettuce in a meal outside the home and being a case (odds ratio 23·7, 95% confidence interval 1·4–404·3). This exposure was reported by 57% of cases. Although over 300 food samples were tested, none yielded any Salmonella spp. Complexity and limited traceability in salad vegetable distribution hindered further investigation of the ultimate source of the outbreak.

Within-household transmission of Escherichia coli may contribute to the pathogenesis of urinary tract infection but understanding of transmission is limited by the lack of longitudinal data on individual shedding patterns. In this study, faecal E. coli was isolated over 6 months from 18 humans and 13 dogs in eight households. Typing 322 E. coli isolates by amplified fragment length polymorphism showed high overall diversity as indicated by the average diversity index (0·66). However, individual shedding patterns varied considerably: two persons carried a single resident E. coli clone throughout the study whereas distinct clones were isolated from other individuals on each sampling time. Nineteen clones were shared within six of the eight households and seven of these clones were shared between humans and dogs. The frequent sharing of clones belonging to phylotypes B2 (n=7) or D (n=4) supports the hypothesis that urovirulent E. coli are transmitted between household members, including dogs, or may be acquired by a common source such as food.

In this prospective cluster randomized controlled trial we evaluated the impact of short-term provision of enhanced infection control support on infection control practice in nursing homes in South London. Twelve nursing homes were recruited, six each in intervention (300 residents) and control (265 residents) groups. Baseline observations of hand hygiene facilities, environmental cleanliness and safe disposal of clinical waste showed poor compliance in both groups. Post-intervention observations showed improvement in both groups. There was no statistical difference between the two groups in the compliance for hand hygiene facilities (P=0·69); environmental cleanliness (P=0·43) and safe disposal of clinical waste (P=0·96). In both groups, greatest improvement was in compliance with safe disposal of clinical waste and the least improvement was in hand hygiene facilities. Since infection control practice improved in intervention and control groups, we could not demonstrate that provision of short-term, enhanced, infection control support in nursing homes had a significant impact in infection control practice.

Most studies reporting pneumonia morbidity are restricted to hospitalized patients, although only a minority of pneumonia patients are admitted to hospital. To get a better understanding of the burden of disease in the general population, we conducted a population-based retrospective study to examine trends in pneumonia incidence in general practice, hospitalization, and mortality due to pneumonia in The Netherlands between 1997 and 2007. Between 2001/2002 and 2006/2007 there was an adjusted yearly increase of 12% in the clinical diagnosis of pneumonia in patients consulting general practitioners. Hospitalizations increased 5% per year between 1999/2000 and 2006/2007, while mortality annually decreased by 2% between 1997/1998 and 2006/2007. Our study suggests that the morbidity of pneumonia in the Dutch population increased considerably over this period, especially in primary-care settings, and that focusing only on hospitalization might underestimate the increasing public health burden of pneumonia.

In Baden-Wuerttemberg, a federal state in south-west Germany, a large outbreak of 1089 laboratory-confirmed human Puumala virus (PUUV) infections occurred in 2007. We conducted a survey to describe the disease burden and a case-control study to identify risk factors for acquiring PUUV. Case-patients were interviewed about clinical outcome and both case-patients and randomly recruited controls were interviewed about exposure. We calculated matched odds ratios (mOR) using a conditional logistic regression model. Multivariable analysis of 191 matched case-control pairs showed that case-patients were more likely than controls to have seen small rodents/their droppings (mOR 1·9, 95% CI 1·2–3·0), cleaned utility rooms (mOR 1·8, 95% CI 1·0–3·4) and visited forest shelters (mOR 3·9, 95% CI 1·1–14·3). Two thirds of case-patients required hospitalization. During PUUV epidemics rodent control measures and use of protective equipment should be considered in utility rooms and shelters.

Ross River virus (RRV) infection is the most common notifiable vector-borne disease in Australia, with around 6000 cases annually. This study aimed to examine the relationship between climate variability and notified RRV infections in the Riverland region of South Australia in order to set up an early warning system for the disease in temperate-climate regions. Notified data of RRV infections were collected by the South Australian Department of Health. Climatic variables and monthly river flow were provided by the Australian Bureau of Meteorology and South Australian Department of Water, Land and Biodiversity Conservation over the period 1992–2004. Spearman correlation and time-series-adjusted Poisson regression analysis were performed. The results indicate that increases in monthly mean minimum and maximum temperatures, monthly total rainfall, monthly mean Southern Oscillation Index and monthly flow in the Murray River increase the likelihood, but an increase in monthly mean relative humidity decreases the likelihood, of disease transmission in the region, with different time-lag effects. This study demonstrates that a useful early warning system can be developed for local regions based on the statistical analysis of readily available climate data. These early warning systems can be utilized by local public health authorities to develop disease prevention and control activities.

The importance of carrier animals (those in whom virus persists after recovery from disease or acute infection) and their potential role in the spread of disease remain open questions within foot-and-mouth disease epidemiology. Using simple probabilistic models we attempt to quantify the effect of emergency vaccination – and especially the time of application – on the likely number of such animals, using data from challenge experiments on both cattle and sheep to determine the probability of persistence in diseased and subclinically infected animals. We show that the number of persistently infected animals in a group is predominantly determined by the number of animals initially infected on premises – the high variability of which ultimately limits the accuracy of any predictions of carrier numbers based upon transmission models. Furthermore, results suggest that, within a cattle herd, carrier numbers may be increased if challenge occurs shortly after vaccination. We show that the quality of inspection is the principal factor influencing whether or not carrier herds occur and that, by reducing clinical signs, the application of vaccination in regularly checked stock also results in an increase in undetected persistently infected animals. Where clinical detection would be poor regardless of the use of vaccination (i.e. particularly in sheep), vaccination will result in a reduction in the probability of a group containing undetected carriers: otherwise there is a benefit only if vaccination is applied sufficiently far in advance of any challenge. The implications of the results for serosurveillance are discussed, including the requisite test sensitivity and practices for successful implementation.

Classical swine fever (CSF) is a disease of pigs that imposes major hardship on the industry of infected regions. The recent history of CSF epidemics suggests that animal movements remain the main source of CSF virus (CSFV) infection for susceptible populations in Europe. This study presents an assessment of the risk of introducing CSFV into Spain through the importation of live susceptible animals. Results suggest that, if prevailing conditions persist, introduction of CSFV into Spain is likely to occur on average every 9 years and that introduction is almost three times more likely to occur via domestic pigs than through wild boars. The highest risk was concentrated in March and in the Northeastern provinces of Spain. Results were consistent with the time and location of previous CSFV introductions into the country. The methodology and the results presented here will contribute to improve the CSF prevention programme in Spain.

Cutaneous leishmaniasis caused by various species of Leishmania is a significant zoonotic disease in many parts of the world. We describe the first cases of Australian cutaneous leishmaniasis in eight northern wallaroos, one black wallaroo and two agile wallabies from the Northern Territory of Australia. Diagnosis was made through a combination of gross appearance of lesions, cytology, histology, direct culture, serology and a species-specific real-time PCR. The causative organism was found to be the same unique species of Leishmania previously identified in red kangaroos. These clinical findings provide further evidence for the continuous transmission of the Australian Leishmania species and its presence highlights the importance of continued monitoring and research into the life-cycle of this parasite.