Decline In Incidence Of Disease Research Articles

Efficiency of bio-agents and green-synthesized silver nanoparticles in controlling purple blotch disease caused by Alternaria porri in onion plants

One of the most fatal diseases that harm Allium species is purple blotch, which is brought on by Alternaria porri. As the disease's severity rises, crop production may decrease. In this study, 12 isolates of A. porri exhibiting purple blotch symptoms have been isolated from diseased onion plants. Sequencing of the internal transcribed spacer region (ITS) allowed for the identification of the isolate that was the most virulent and caused a disease severity of 85.93%. Under greenhouse and field growing conditions, the efficiency of two bio-agents, Trichoderma asperellum T34 and Saccharomyces cerevisiae AUMC 10203, as well as three doses (50, 25, and 12.5 ppm) of their green-synthesized silver nanoparticles (AgNPs) against purple blotch disease was assessed. For avoiding or treating purple blotch disease in onion plants, it has been demonstrated that the T. asperellum T34 spore suspension was the most effective resulting in a 76% reduction in disease severity. The spore suspension of S. cerevisiae and a 50-ppm dosage of AgNPs were the top contenders for T. asperellum. When compared to the control plants, the plants treated with bio-agents and AgNPs showed a significant decline in disease incidence and disease severity. Additionally, improvements were made to the broadness of inflorescences, the number of flowers and seeds, the weight of seeds per inflorescence, and the seed productivity. Therefore, it is recommended in this study to use T. asperellum T34 spore suspension as a potent bio-agent to manage the symptoms of purple blotch on onions.

Launch and Post-Launch Prices of Injectable Cancer Drugs in the US: Clinical Benefit, Innovation, Epidemiology, and Competition.

Rising cancer drug prices adversely affect patients' adherence and survival. We aimed to identify and quantify factors associated with launch prices and post-launch price changes of injectable cancer drugs in the US from 2005 to 2023. All anticancer drugs with US FDA approval between 2000 and 2022 were identified in the Drugs@FDA database. The sample was then restricted to cancer drugs covered under Medicare Part B (injectable drugs). Data characterizing each drug's clinical benefits, disease epidemiology, approved indications, competition, and price were obtained from FDA labels, the Global Burden of Disease study, and the Centers for Medicare and Medicaid Services. The association between launch/post-launch prices and collected variables was assessed in random-effects regressions. Of 170 cancer drugs with FDA approval between 2000 and 2022, we identified 66 (39%) injectable cancer drugs with quarterly price data from 2005 to 2023. In 2023, mean prices amounted to $27,688 per month, with an average price increase of 94% from 2005 to 2023. Launch and post-launch price changes were significantly associated with the treated disease epidemiology. A 1% decline in disease incidence was associated with a 0.2511% (p=0.008) increase in launch prices and a 0.0086% (p=0.032) annual increase in post-launch prices. Accordingly, launch prices were 120% (p=0.051) higher for orphan than non-orphan drugs, with 3% (p=0.008) greater annual post-launch price increases. Post-launch prices declined by up to -2% annually as new supplemental indications were approved for the same drug. We found no consistent association between launch/post-launch prices and the drugs' clinical benefit in terms of overall survival, progression-free survival, and tumor response. The market entry of new competitors was not associated with price reductions. 28 of 33 drug pairs within the same class had positive correlation coefficients. Pearson correlation coefficients were high (>0.80) for PD-1/PD-L1 inhibitors, CD38 antibodies, CD20 antibodies, HER2 antibodies, and mTOR inhibitors. Cancer drug prices regularly increase faster than inflation; however, there is no evidence that launch prices and post-launch price changes are aligned with the clinical benefit a drug offers to patients. In particular, patients with rare diseases experience greater price increases for their orphan drugs. There is no evidence that brand-brand competition results in drug price reductions.

Declining Rates of Legg-Calvé-Perthes Surgery in the United States: National Trends Using the Kids' Inpatient Database and Pediatric Health Information System.

In 2004 and 2008 two large prospective, multicenter studies were published which resulted in improved understanding of operative indications for the treatment of Legg-Calvé-Perthes disease (LCPD) based on patient age, disease severity, and resultant radiographic outcomes. The primary aim of this study is to evaluate the trends in surgical management of LCPD in the United States prior, and subsequent to, the publication of these landmark studies. Cross-sectional retrospective analysis of US pediatric hospitalizations for the surgical management of LCPD was conducted using the Kids' Inpatient Database from 2000 to 2016. Patients 12 years of age and younger were included who had a primary admission diagnosis of LCPD and a LCPD-related procedure during the hospitalization. Data was subsequently weighted to produce national-level estimates and variables pertaining to patient age group, procedure, demographics, and hospital characteristics were analyzed. In a post hoc analysis, the results of the Kids' Inpatient Database were also corroborated with the Pediatric Health Information System database. A weighted sample of 2786 LCPD surgical admissions met inclusion and exclusion criteria; 11.2% of surgical admissions were patients below 6 years of age, 35.9% were 6 to 8 years of age, and 52.9% were above 8 years of age. There was a significant decrease in admissions for surgical management of LCPD in all age groups over time, however there was no appreciable change in the proportion of LCPD surgical admissions performed among the above 8 to below 12, above 6 to below 8, or below 6 years age groups. Femoral osteotomy remained the most common surgical procedure, while other osteotomy types, including pelvic and unspecified osteotomies involving the hip, decreased over time ( P <0.001). There is a decreasing rate of hospital admissions for LCPD surgery since 2000, perhaps indicating a decline in incidence of disease. Furthermore, despite evidence supporting LCPD surgical outcomes related to patient age, there has been no change in the proportion of patients undergoing surgery by age group over time. Level III-retrospective study.

Cashew leaf and nut blight disease outbreaks under unimodal rainfall pattern in Tanzania

Cashew (Anacardium occidentale L.) which is an important cash crop in Tanzania, is susceptible to various abiotic and biotic stresses. Cashew leaf and nut blight disease caused by Cryptosporiopsis spp. is a devastating disease of cashew crop resulting in a significant reduction of nut production. We conducted a study to assess the association between weather variables, particularly rainfall and temperature, on cashew leaf and nut blight disease (CLNBD) outbreaks and establish a minimum wetness duration period for initiation and development of the disease. Poisson regression analysis indicated a significant association between rainfall and temperature with CLNBD incidence (df = 3, Chi Pr < 0.001). Rainfall was positively associated with CLNBD and a unit increase of 1 mm in rainfall caused a 2 percent increase in the percentage of disease incidence (e = + 0.01995, p < 0.011). However, temperature was negatively associated with disease incidence and a unit increase of 1 °C in temperature caused a 21.56% decline in disease incidence (e = –0.2428, p < 0 .001). Blight incidence was significantly higher (p < 0.001) during the rainy season (range: 11.7 to 36.6%) compared to the dry season (1.4 to 11.5%). Cashew trees in Mtwara District recorded higher blight disease incidence as compared to the rest of the studied areas. This study also established that symptoms for blight disease on cashew leaves appear 8 h post exposure to continuous wet periods. Thus, it appears that for the blight pathogen to initiate and complete its infection processes, a continuous wet period of at least 8 h is required. Findings from this study, particularly the association of rainfall and temperature on disease epidemics, can be used as tools for forewarning incidences of CLNBD. This would help timely initiation of appropriate management strategies.

Unraveling the invisible leptospirosis in mainland Southeast Asia and its fate under climate change

Leptospirosis is a neglected waterborne zoonosis of growing concern in tropical and low-income regions. Endemic in Southeast Asia, its distribution and environmental factors such as climate controlling its dynamics remain poorly documented. In this paper, we investigate for the first time the current and future leptospirosis burden at a local scale in mainland Southeast Asia. We adjusted machine-learning models on incidence reports from the Thai surveillance system to identify environmental determinants of leptospirosis. The explanatory variables tested in our models included climate, topographic, land cover and soil variables. The model performing the best in cross-validation was used to estimate the current incidence regionally in Thailand, Myanmar, Cambodia, Vietnam and Laos. It then allowed to predict the spatial distribution of leptospirosis future burden from 2021 to 2100 based on an ensemble of CMIP6 climate model projections and 4 Shared Socio-economics Pathways ranging from the most optimistic to the no-climate policy outcomes (SSP1–2.6, SSP2–4.5, SSP3–7.0 and SSP5–8.5). Leptospirosis incidence was best estimated by 10 environmental variables: four landscape-, four rainfall-, two temperature-related variables. Of all tested scenario, the worst-case scenario of climate change (SSP5–8.5) surprisingly appeared as the best-case scenario for the future of leptospirosis since it would induce a significant global decline in disease incidence in Southeast Asia mainly driven by the increasing temperatures. These global patterns are however contrasted regionally with some regions showing increased incidence in the future. Our work highlights climate and the environment as major drivers of leptospirosis incidence in Southeast Asia. Applying our model to regions where leptospirosis is not routinely monitored suggests an overlooked burden in the region. As our model focuses on leptospirosis responses to environmental drivers only, some other factors, such as poverty, lifestyle or behavioral changes, could further influence these estimated future patterns.

English

The damaging potential of Alternaria alternata on different mungbean genotypes was accessed and its management was done under in vitro and in vivo conditions through suitable fungicides. Seeds of fifty different mungbean genotypes were sown in lines. There were fifteen replications for each line. The data on disease incidence and percent disease intensity were accessed on all the genotypes. Infection was observed on all genotypes, none of them were found to be immune. Fourteen lines were found to be the most susceptible (14114, 14117, 14128, 14198, 14203, 14205, 14250, 14265, 14266, 14295, 14305, 14306, 14368, 14438). Infection was observed on all genotypes, none of them were found to be immune. The maximum PDI (Percent Disease Intensity) was recorded 35.30% while minimum was 2.43%. For detached leaf assay, the conidial suspension of 105 conidia/mLwas prepared and sprayed on detached leaves. The results revealed that maximum infection percentage was observed in 14306, 14198 genotypes while minimum was observed in 14128, 14203. The lesion area was found to be maximum in 14306, 14198 (0.23, 0.22) while minimum in 14128 (0.12) respectively. For management experiments, different fungicides; Propiconazole (Tilt), Propineb (Antracol), Difenconazole (Score), Thiophanate methyl (Topsin M), Mancozeb (Dithane M45) were tested under in vitro and in vivo conditions. Significant decrease in mycelial growth with the increase in concentration of fungicides was observed. Percent inhibition of mycelial growth was maximum in Propiconazole at its highest concentration (1000 ppm) under in vitro conditions. A significant decline in disease incidence was observed as compared to control treatment. The minimum percent disease incidence was recorded in Propiconazole (10.34) with PDC (67.31) while the maximum percent disease incidence was observed in Thiophanate methyl (25.46). So, Propiconazole could be used successfully for the management of A. alternata under field conditions.

Disease influences host population growth rates in a natural wild plant–pathogen association over a 30‐year period

Abstract The epidemiological and demographic dynamics of plant–pathogen interactions in natural environments are strongly affected by spatial and temporal influences. Here we assess the interaction between Filipendula ulmaria and its rust pathogen Triphragmium ulmariae by analysing a 30‐year long dataset that has followed pathogen and plant population dynamics in a metapopulation of ~230 host patches growing on islands of the Skeppsvik archipelago in northern Sweden. Over this period, the host metapopulation initially expanded in both number and size of individual patches before plateauing. In contrast, the pathogen metapopulation showed greater change. Disease incidence showed a convex pattern rising for the first decade before showing a marked decline in the last decade. At the same time, the prevalence of disease in infected populations showed a constant 30‐year long decline. At the individual host population level, each population was annually classified into one of four inter‐year states: healthy, recolonization, extinction and diseased. Host populations that were healthy from 1 year to the next were significantly smaller than all other host population categories, while host populations in which disease was constantly present were significantly larger. Host populations in which the pathogen underwent either an extinction or a recolonization event were of similar size and represented a measure of the host threshold size for long‐term pathogen survival. Host population growth rates declined as disease levels increased. The growth rate of host populations in which disease was continuously present was 75% lower than in populations that were free disease. The sensitivity of the association to climate change as demonstrated through a decline in disease incidence and prevalence and an increase in drought damage to plant populations as temperatures rise has only become apparent through analysis of an extensive long‐term dataset. Synthesis. To date wild plant–pathogen studies have focused on the epidemiology of the pathogen and its effect on individual plant fitness. Here we have established a link to the impact of the pathogen on the long‐term dynamics of host populations. This has the potential to trigger a cascade of changes in the species composition and diversity of communities.

Management of Root Rot (Rhizoctonia solani) of Mothbean through Bio-Agents

Root rot caused by Rhizoctonia solani is an important disease of mothbean, under severe infestation it causes 58-68 % losses in grain yield. Three-year field experiments were conducted in hot arid conditions at Bikaner, Rajasthan during kharif seasons with the objective to find out suitable eco-friendly management strategies for root rot. The experiment was conducted on cv. RMO-225 with six different combination of Trichoderma harzianum + Pseudomonas fluorescens bio- agents viz, seed treatment, soil treatment and their combinations against the root rot disease and compared with an untreated control. Results of experiment showed that all the treatments brought significant decline in disease incidence and consequently enhancement of grain yield compared to control. The treatment having combination of Trichoderma harzianum + Pseudomonas fluorescens seed treatment (4+4 g/kg seed) + soil application of T. harzianum + P. fluorescens (1.25 +1.25 kg in 50 kg FYM for each/ha) had minimum (21.78 %) root rot incidence, highest grain yield (10.56 q /ha) and net return (Rs. 14,338/ha). The T. harzianum seed treatment 8 g/kg seed + soil application of T. harzianum 2.5kg in 100 kg FYM/ha was the next best treatment with 25.56 per cent disease incidence and 9.42 q/ha of grain yield. These treatments can provide an effective, economical and eco- friendly management of root rot of mothbean for cultivators.

Trends in diarrhoeal disease hospitalisation in a paediatric short - stay ward at a tertiary-level hospital in Soweto: 2002-2016

Globally, a decline in diarrhoeal disease has been observed over the last two decades. This may be attributable to several interventions, including rotavirus vaccination since 2009 in South Africa. From January 2002 to December 2016, we conducted a retrospective trend analysis of diarrhoeal hospitalisations with mild or moderate dehydration to a short-stay ward (SSW) in children <14 years of age. We found that diarrhoeal hospitalisation to the SSW accounted for 29.3% of the 53 717 children who presented with diarrhoea to the emergency department. A significant decline in disease incidence was noted after 2009/2010, coinciding with rotavirus vaccine implementation into the Expanded Programme on Immunisation. The yearly incidence (per 100 000) declined from 307 (95% confidence interval (CI) 277 - 337) over the 2002/2008 period to 141 (95% CI 120 - 161) from 2011/2016; p <0.001. In conclusion, rotavirus vaccination was associated with a decline of diarrhoeal disease hospitalisations to the SSW at this hospital.

Insecticide-treated nets for preventing malaria.

A previous version of this Cochrane Review identified that insecticide-treated nets (ITNs) are effective at reducing child mortality, parasite prevalence, and uncomplicated and severe malaria episodes. Insecticide-treated nets have since become a core intervention for malaria control and have contributed greatly to the dramatic decline in disease incidence and malaria-related deaths seen since the turn of the millennium. However, this time period has also seen a rise in resistance to pyrethroids (the insecticide used in ITNs), raising questions over whether the evidence from trials conducted before resistance became widespread can be applied to estimate the impact of ITNs on malaria transmission today. The primary objective of this review was to assess the impact of ITNs on mortality and malaria morbidity, incorporating any evidence published since the previous update into new and existing analyses, and assessing the certainty of the resulting evidence using GRADE. We searched the Cochrane Infectious Diseases Group Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL) published in the Cochrane Library, MEDLINE, Embase, LILACS, the World Health Organization (WHO) International Clinical Trials Registry Platform, ClinicalTrials.gov, and the ISRCTN registry for new trials published since 2004 and up to 18 April 2018. We included individual randomized controlled trials (RCTs) and cluster RCTs comparing bed nets or curtains treated with a synthetic pyrethroid insecticide at a minimum target impregnation dose recommended by the WHO with no nets or untreated nets. One review author assessed the identified trials for eligibility and risk of bias, and extracted data. We compared intervention and control data using risk ratios (RRs), rate ratios, and mean differences, and presented all results with their associated 95% confidence intervals (CIs). We assessed the certainty of evidence using the GRADE approach. We drew on evidence from a meta-analysis of entomological outcomes stratified by insecticide resistance from 2014 to inform the GRADE assessments. Our updated search identified three new trials. A total of 23 trials met the inclusion criteria, enrolling more than 275,793 adults and children. The included studies were conducted between 1987 and 2001.ITN versus no netsInsecticide-treated nets reduce child mortality from all causes by 17% compared to no nets (rate ratio 0.83, 95% CI 0.77 to 0.89; 5 trials, 200,833 participants, high-certainty evidence). This corresponds to a saving of 5.6 lives (95% CI 3.6 to 7.6) each year for every 1000 children protected with ITNs. Insecticide-treated nets also reduce the incidence of uncomplicated episodes of Plasmodium falciparum malaria by almost a half (rate ratio 0.55, 95% CI 0.48 to 0.64; 5 trials, 35,551 participants, high-certainty evidence) and probably reduce the incidence of uncomplicated episodes of Plasmodium vivax malaria (risk ratio (RR) 0.61, 95% CI 0.48 to 0.77; 2 trials, 10,967 participants, moderate-certainty evidence).Insecticide-treated nets were also shown to reduce the prevalence of P falciparum malaria by 17% compared to no nets (RR 0.83, 95% CI 0.71 to 0.98; 6 trials, 18,809 participants, high-certainty evidence) but may have little or no effect on the prevalence of P vivax malaria (RR 1.00, 95% CI 0.75 to 1.34; 2 trials, 10,967 participants, low-certainty evidence). A 44% reduction in the incidence of severe malaria episodes was seen in the ITN group (rate ratio 0.56, 95% CI 0.38 to 0.82; 2 trials, 31,173 participants, high-certainty evidence), as well as an increase in mean haemoglobin (expressed as mean packed cell volume) compared to the no-net group (mean difference 1.29, 95% CI 0.42 to 2.16; 5 trials, 11,489 participants, high-certainty evidence).ITN versus untreated netsInsecticide-treated nets probably reduce child mortality from all causes by a third compared to untreated nets (rate ratio 0.67, 95% CI 0.36 to 1.23; 2 trials, 25,389 participants, moderate-certainty evidence). This corresponds to a saving of 3.5 lives (95% CI -2.4 to 6.8) each year for every 1000 children protected with ITNs. Insecticide-treated nets also reduce the incidence of uncomplicated P falciparum malaria episodes (rate ratio 0.58, 95% CI 0.44 to 0.78; 5 trials, 2036 participants, high-certainty evidence) and may also reduce the incidence of uncomplicated P vixax malaria episodes (rate ratio 0.73, 95% CI 0.51 to 1.05; 3 trials, 1535 participants, low-certainty evidence).Use of an ITN probably reduces P falciparum prevalence by one-tenth in comparison to use of untreated nets (RR 0.91, 95% CI 0.78 to 1.05; 3 trials, 2,259 participants, moderate-certainty evidence). However, based on the current evidence it is unclear whether or not ITNs impact on P vivax prevalence (1 trial, 350 participants, very low certainty evidence) or mean packed cell volume (2 trials, 1,909 participants, low certainty evidence). Although there is some evidence that insecticide resistance frequency has some effects on mosquito mortality, it is unclear how quantitatively important this is. It appeared insufficient to downgrade the strong evidence of benefit on mortality and malaria illness from the trials conducted earlier.

Human African trypanosomiasis in the Democratic Republic of the Congo: disease distribution and risk.

BackgroundFor the past three decades, the Democratic Republic of the Congo (DRC) has been the country reporting the highest number of cases of human African trypanosomiasis (HAT). In 2012, DRC continued to bear the heaviest burden of gambiense HAT, accounting for 84 % of all cases reported at the continental level (i.e., 5,968/7,106). This paper reviews the status of sleeping sickness in DRC between 2000 and 2012, with a focus on spatio-temporal patterns. Epidemiological trends at the national and provincial level are presented.ResultsThe number of HAT cases reported yearly from DRC decreased by 65 % from 2000 to 2012, i.e., from 16,951 to 5,968. At the provincial level a more complex picture emerges. Whilst HAT control in the Equateur province has had a spectacular impact on the number of cases (97 % reduction), the disease has proved more difficult to tackle in other provinces, most notably in Bandundu and Kasai, where, despite substantial progress, HAT remains entrenched. HAT prevalence presents its highest values in the northern part of the Province Orientale, where a number of constraints hinder surveillance and control.Significant coordinated efforts by the National Sleeping Sickness Control Programme and the World Health Organization in data collection, reporting, management and mapping, culminating in the Atlas of HAT, have enabled HAT distribution and risk in DRC to be known with more accuracy than ever before. Over 18,000 locations of epidemiological interest have been geo-referenced (average accuracy ≈ 1.7 km), corresponding to 93.6 % of reported cases (period 2000–2012). The population at risk of contracting sleeping sickness has been calculated for two five-year periods (2003–2007 and 2008–2012), resulting in estimates of 33 and 37 million people respectively.ConclusionsThe progressive decrease in HAT cases reported since 2000 in DRC is likely to reflect a real decline in disease incidence. If this result is to be sustained, and if further progress is to be made towards the goal of HAT elimination, the ongoing integration of HAT control and surveillance into the health system is to be closely monitored and evaluated, and active case-finding activities are to be maintained, especially in those areas where the risk of infection remains high and where resurgence could occur.Electronic supplementary materialThe online version of this article (doi:10.1186/s12942-015-0013-9) contains supplementary material, which is available to authorized users.

Spatiotemporal Characterization of Sclerotinia Crown Rot Epidemics in Pyrethrum.

Sclerotinia crown rot, caused by Sclerotinia minor and S. sclerotiorum, is a disease of pyrethrum in Australia that may cause substantial decline in plant density. The spatiotemporal characteristics of the disease were quantified in 14 fields during three growing seasons. Fitting the binary power law to disease incidence provided slope (b = 1.063) and intercept (ln(Ap) = 0.669) estimates significantly (P ≤ 0.0001) greater than 1 and 0, respectively, indicating spatial aggregation at the sampling unit scale that was dependent upon disease incidence. Covariate analyses indicated that application of fungicides did not significantly influence these estimates. Spatial autocorrelation and spatial analysis by distance indices indicated that spatial aggregation above the sampling unit scale was limited to 20 and 17% of transects analyzed, respectively. The range of significant aggregation was limited primarily to neighboring sampling units only. Simple temporal disease models failed to adequately describe disease progress, due to a decline in disease incidence in spring. The relationships between disease incidence at the scales of individual plants within quadrats and quadrats within a field was modeled using four predictors of sample size. The choice of the specific incidence-incidence relationship influenced the classification of disease incidence as greater than or less than 2% of plants, a provisional commercial threshold for fungicide application. Together, these studies indicated that epidemics of Sclerotinia crown rot were dominated by small-scale aggregation of disease. Larger scale patterns of diseased plants, when present, were associated with severe disease outbreaks. The spatial and temporal analyses were suggestive of disease epidemics being associated with localized primary inoculum and other factors that favor disease development at a small scale.

Effect of some factors on the incidence of choke (Epichloë typhina) in grass seed stands in the Czech Republic

Choke of grasses caused by Epichlo&amp;euml; typhina occurred in 2008 and 2009 in more than 25% of grass seed stands of timothy (Phleum pratense and P. nodosum); a lower incidence was reported in orchard grass (Dactylis glomerata). A decline in disease incidence in 2010 was caused partly by a reduction in the total area of grasses grown for seed production and partly by a decrease of older grass seed stands. The incidence of choke in timothy varieties Odenw&amp;auml;lder and Pampas was very high; they differed statistically from the other 24 grown cultivars. No difference was found among 21 varieties of orchard grass. The highest incidence of choke was observed in varieties Comer and Dolina (timothy) and Amera (orchard grass). The incidence of choke in cultivated varieties of Phleum spp. and D. glomerata was affected by stand age (the incidence of the disease in timothy was recorded in 13% of stands in the first cropping year and in 50% of stands in the fifth cropping year). Choke disease occurred in all regions where the species were grown for seed. &amp;nbsp;

Perthes' disease: deprivation and decline

IntroductionPerthes' disease is a childhood hip disorder which frequently precipitates premature osteoarthritis necessitating joint replacement in young adults. The highest incidence reported worldwide is in Merseyside, UK, where a unique...

Pathogenesis of Contact Lens-Associated Microbial Keratitis

Sight-threatening microbial keratitis associated with contact lens wear remains a serious concern for patients, eye-care practitioners, and the contact lens industry. Several decades of research and some major advances in lens and solution technology have not resulted in a decline in disease incidence. Here, we offer a perspective on the complex pathogenesis of microbial keratitis, the factors that have prevented a better understanding of this disease, and new approaches being used to tackle this important clinical problem.

The Sounds of Silence: Public Goods, Externalities, and the Value of Infectious Disease Control Programs

Professionals who devote their careers to the control of communicable diseases, whether in the community or hospital setting, are assured an endless and varied series of challenges due to the dynamic nature of microbial populations, the mobility of human populations, and technological changes that facilitate the emergence, identification and quantification of emerging infectious disease threats. However, many practitioners working in hospital epidemiology or public health have experienced the following frustration: the incidence of an infectious process has been reduced or eliminated through application of a successful control program (eg, the introduction of vaccination or active surveillance for carriage of antimicrobial resistant pathogens). As the threat of the disease in question (whether measles or infection with health care-associated methicillin-resistant Staphylococcus aureus [MRSA]) declines, administrators or program participants question the necessity of the program, with subsequent erosion of resources and support. The opposite may occur: elimination of disease surveillance programs or case-finding efforts may result in an apparent decline in disease incidence, with a resultant pat on the back from administrators for a job well done. A number of examples of this phenomenon, drawn from recent newspaper headlines, come to mind. In Ontario, the legal requirement that cheeses be pasteurized (a health measure that has been successful in diminishing serious foodborne illness) has been criticized, even in the face of contradictory calls for ‘enhanced food safety’ following the province’s role in the recent pan-Canadian listeriosis outbreak (1,2). Resurgences have been identified in historically well-controlled vaccine-preventable diseases, including rubella, measles, mumps and pertussis in the face of increasing popular concern that the risks of vaccination do not outweigh the benefits when disease is uncommon (3). Perhaps the most poignant example of this phenomenon involves an Ontario health ministry spokesperson who, a year before severe acute respiratory syndrome (SARS) exposed gaps in that province’s public health capacity, justified cuts to the province’s public health laboratory as follows: “Do we want five people sitting around waiting for work to arrive? It would be highly unlikely that we would find a new organism in Ontario” (4). Complicating matters further, rapid growth of costs in health care (5) have resulted in demands that health programs, including those that target infectious disease prevention and control, justify their roles through demonstration of cost-neutrality, or even revenue generation. For example, a recent document produced by a working group of the Society for Hospital Epidemiology of America provided guidance to health care professionals on the construction of ‘business cases’ to justify hospital infection control budgets (6). To summarize this paradoxical state of affairs, control of infectious diseases requires active, ongoing intervention, but disease control successes manifest as the nonoccurrence of events (ie, silence). Maintenance of such silence requires active investment, but decision-makers and the public may be reluctant to invest when ‘nothing is happening’. Public health crises, including outbreaks and epidemics, result in a booster dose of interest, funding, and resources, but at a high cost (both health and monetary). We propose that the first step toward remedying this state of affairs lies in the recognition that maintenance of communicable disease control, in a jurisdiction or hospital, represents a type of ‘public good’. The economic framework that has previously been created to maintain other public goods (such as urban infrastructure or clean water) may have value if applied to communicable disease control.

Holdover Inoculum of Pseudomonas syringae pv. alisalensis from Broccoli Raab Causes Disease in Subsequent Plantings.

Uniform plots of broccoli raab (Brassica rapa subsp. rapa) seedlings were inoculated with a rifampicin-resistant strain of Pseudomonas syringae pv. alisalensis, the causal agent of bacterial blight on crucifers, resulting in 100% disease incidence in mature plants. Diseased plants were incorporated into the soil at maturity and smaller replicated plots were replanted at various times after incorporation. Rifampicin-resistant fluorescent pseudomonads with rep-PCR profiles identical to P. syringae pv. alisalensis were isolated from lesions on plants grown in soil into which the first diseased crop was incorporated. Disease incidence declined in mature plants as the length of time between incorporation of the first planting and seeding of the replanted plots increased. Bacterial population levels in soil decreased over time and bacteria were no longer detectable 3 weeks after incorporation of the diseased crop. In laboratory tests, population levels of P. syringae pv. alisalensis decreased in untreated soil but not in autoclaved soil. Greenhouse studies demonstrated a direct correlation between population levels of P. syringae pv. alisalensis applied to soil and disease incidence in seedlings. However, the decline in bacterial populations in field soils did not wholly account for the decline in disease incidence with subsequent plantings.

Use of a computerized database to study the effectiveness of an attenuated varicella vaccine.

The varicella vaccine Varilrix (GlaxoSmithKline) was introduced in Israel in June 2000 as an optional vaccination for children. We used the database of a single health maintenance organization that serves 25% of the population in Israel to assess the effectiveness of the vaccine retrospectively. Incidence and complications of varicella were derived from the database from January 1, 1998 until December 31, 2002. Since licensure >30000 individuals younger than 10 years in this health maintenance organization have been immunized with the vaccine. Annual incidence of disease per 1000 in the study population was 86.6 in 1998, 74.6 in 1999, 74.0 in 2000, 37.1 in 2001 and 44.6 in 2002. This declining trend in incidence of disease was statistically significant. Complications of varicella occurred in approximately 1% of patients throughout the 5-year study period, but there was a parallel decline in the number of patients with complications corresponding to the decline in disease incidence. Vaccine effectiveness for prevention of clinical disease in this population was 92% (95% confidence interval, 91.0 to 92.7). There were varying rates of utilization within communities of varied socioeconomic class, so that in the higher socioeconomic class there was an increased utilization and a corresponding decrease of attack rate; whereas in communities where there were lower utilization rates, corresponding increased numbers of varicella cases were seen. This database enables long term follow-up of the effectiveness of this vaccine in a large population.

Role of China in the quest to define and control severe acute respiratory syndrome.

China holds the key to solving many questions crucial to global control of severe acute respiratory syndrome (SARS). The disease appears to have originated in Guangdong Province, and the causative agent, SARS coronavirus, is likely to have originated from an animal host, perhaps sold in public markets. Epidemiologic findings, integral to defining an animal-human linkage, may then be confirmed by laboratory studies; once animal host(s) are confirmed, interventions may be needed to prevent further animal-to-human transmission. Community seroprevalence studies may help determine the basis for the decline in disease incidence in Guangdong Province after February 2002. China will also be able to contribute key data about how the causative agent is transmitted and how it is evolving, as well as identifying pivotal factors influencing disease outcome. There must be support for systematically addressing these fundamental questions in China and rapidly disseminating results.

Chickpea in wheat-based cropping systems of northern New South Wales. II. Influence on biomass, grain yield, and crown rot in the following wheat crop

Rotational effects of chickpea, an important N2-fixing pulse legume of the northern grains region, on subsequent wheat require quantification of the contribution of the legume to soil N and the N status of the wheat, and of suppression of soil and stubble-borne pathogens, such as crown rot (Fusarium graminearum Schwabe Group 1). Results from selected treatments of 10 experiments in northern New South Wales in which chickpea and wheat in one season were followed by wheat in following seasons indicated generally higher dry matter (DM) and grain yields of wheat after chickpea than after wheat. Responses to chickpea were -0·8 to 3·3 t/ha (shoot DM) and -3 to 39 kg N/ha (shoot N). Responses in wheat grain yields were -0·1 to 1·7 t/ha (mean 0·85 t/ha); grain N responses were -2 to 33 kg/ha (mean 19 kg/ha). Grain protein responses were small (0·6%) and variable. Although these productivity responses could be explained largely in terms of additional nitrate-N following chickpea, we measured reduced incidences of crown rot in wheat after chickpea (range 1-36%, mean of 12%), compared with wheat after wheat (range 5-52%, mean 30%). Modelling the incidence of crown rot indicated highly significant interactions between prior crop and total water (pre-plant soil water plus in-crop rainfall). When wheat followed chickpea, incidence of the disease declined sharply with increasing water. When wheat followed wheat, there was a marginal decline in disease incidence with increasing water. Our results support the strategy of using legumes in rotation with wheat in the northern grains region for enhanced soil-N supply and disease-break effects.