Major Disease Outbreaks Research Articles

Surveillance for Illness and Injury After Hurricane Katrina—New Orleans, Louisiana, September 8-25, 2005

Hurricane Katrina struck the Gulf Coast on August 29, 2005, resulting in extensive structural damage and severe flooding from breached levees in and around New Orleans, Louisiana. The public health infrastructure of the Louisiana Department of Health and Hospitals (LDHH) was damaged extensively, limiting surveillance for illnesses, injuries, and toxic exposures. On September 9, 2005, LDHH, CDC, and functioning emergency treatment resources (i.e., hospitals, disaster medical assistance teams, and military aid stations) established an active surveillance system to detect outbreaks of disease and characterize post-hurricane injuries and illnesses. As of September 25, the system had monitored 7,508 reports of health-related events at participating facilities. Trends observed in the data prompted investigations of respiratory and rash illnesses, but no major outbreaks of disease or hazardous environmental exposures were detected. These data also were used to identify post-hurricane injury patterns and to guide prevention messages to residents and relief workers. A natural disaster of the magnitude of Hurricane Katrina requires a sustained response and a detailed plan for return to pre-hurricane surveillance activities.

Importance of Escherichia coli Strains Producing Verotoxins

The production of a heat-labile protein unrelated to cholera toxin was described in the 1960s in studies of Escherichia coli isolated from animals (1,2). However, it was not until 1982 when Riley et al. reported an outbreak of haemorrhagic colitis associated with an E. coli that produced the same heat-labile toxin, and that these strains were considered hazardous to humans (3). A second interesting outcome of the study by Riley et al. was that E. coli strains isolated during this outbreak belonged to a serotype that had not been previously associated with human disease. Over the subsequent years, this 'new' serotype, O157:H7, became the predominant causal pathogen worldwide for both haemorrhagic colitis and haemolytic-uraemic syndrome. Outbreaks of haemorrhagic colitis and haemolytic-uraemic syndrome associated with O157:H7 E. coli strains have been reported in Canada, the United States, Europe, and Japan (4). The production of heat-labile cytotoxin is not restricted to E. coli O157:H7, with studies showing that other E. coli strains have this character (5), and the common trait among these bacteria is the ability to produce heat-labile cytotoxin. Such strains have been grouped according to specific characteristics: Verocytotoxin-producing E. coli, which relates to the capacity to destroy monolayers of vero cells in culture; enterohaemorrhagic E. coli for their capacity to cause haemorrhagic colitis and haemolytic-uraemic syndrome; and more recently, Shiga-toxin (Stx)-producing E. coli (STEC) for the similarity of the toxin produced by these E. coli strains with that produced by Shigella dysenteriae type 1 (4). Given the severity of the diseases associated with infection by these strains and their importance as the leading cause of acute renal failure in children aged less than five years in developed countries, an international network of interested laboratories has been established to conduct surveillance and determine the burden of disease associated with these infections. Concerned laboratories in less-developed areas of the world have also joined this international endeavour to determine the importance of such strains as part of the spectrum of diarrhoeal diseases in their own environments. Studies conducted in less-developed areas of the world have already shown little participation of STEC strains as causal agents of diarrhoeal disease in these countries (4). What is interesting is that the conditions for transmission of these strains from animals to humans exist, as do the inherent problems relating to basic sanitation and safe drinking-water. Therefore, the question that remains to be answered is why there has been such a lack of isolation of STEC in these areas. The reason is not due to a lack of technical capacity in participating laboratories or to inadequate surveillance systems in these areas. Active surveillance at the community level has been conducted in several longitudinal surveys of diarrhoeal disease in less-developed countries in which other types of pathogenic strains of E. coli have been properly identified and characterized by state-of-the-art methods (4). Therefore, there has to be another explanation for the lack of participation of STEC as a cause of major outbreaks of disease in these areas of the world. In this issue of JHPN, Voravuthikunchai et al. report the results of a study conducted in Thailand to determine whether the presence of a humoral immune response to O157 lipopolysaccharide (LPS) could be a reason for the lack of disease associated with infection by these strains in people with diarrhoea in that country (6). An IgM response to the O157 LPS was found by these authors in 12% of 332 serum samples obtained from healthy blood donors and patients with diseases unrelated to diarrhoea. In the case of an IgG response, 23% of these same samples showed a positive response to O157 LPS. The authors conclude that possible exposure to cross-reacting antigens in these subjects could be the reason for finding this response in their sera, and a possible protection against colonization and disease associated with O157:H7 strains. …

Analysis of Barmah Forest Virus Disease Activity in Queensland, Australia, 1993–2003: Identification of a Large, Isolated Outbreak of Disease

Barmah Forest virus (BFV) disease is the second most common mosquito-borne disease in Australia. Although the majority of notifications are received from Queensland, little is known about the distribution of the disease within the state, or the important mosquito vectors and nonhuman vertebrate hosts. We conducted a retrospective statistical analysis of the notifications received from Queensland residents from 1993 to 2003 to establish long-term local incidence rates and to identify disease outbreaks. In total, 4,544 notifications were received over the 10-yr period. Disease reporting peaked in autumn, although the peak transmission season encompassed both summer and autumn. Long-term standardized incidence rates for summer/autumn and winter/spring varied across the state, showing positive spatial autocorrelation in both 6-mo periods. Although 15 instances of increased disease activity were identified, only one major disease outbreak affecting eight contiguous local government areas was detected in summer/autumn 2002/2003. This outbreak contained 297 cases, 115 more than would be expected over this period. The factors important to this outbreak are unknown and require further investigation. Although the incidence rates for BFV disease are lower than Ross River virus disease, the most reported mosquito-borne disease in Australia, several factors indicate that this virus should be considered an important public health risk in Queensland. These include consistent endemic transmission, apparent underreporting of the disease, and the potential for outbreaks in major population centers.

Analysis of Barmah Forest Virus Disease Activity in Queensland, Australia, 1993–2003: Identification of a Large, Isolated Outbreak of Disease

Barmah Forest virus (BFV) disease is the second most common mosquito-borne disease in Australia. Although the majority of notifications are received from Queensland, little is known about the distribution of the disease within the state, or the important mosquito vectors and nonhuman vertebrate hosts. We conducted a retrospective statistical analysis of the notifications received from Queensland residents from 1993 to 2003 to establish long-term local incidence rates and to identify disease outbreaks. In total, 4,544 notifications were received over the 10-yr period. Disease reporting peaked in autumn, although the peak transmission season encompassed both summer and autumn. Long-term standardized incidence rates for summer/autumn and winter/spring varied across the state, showing positive spatial autocorrelation in both 6-mo periods. Although 15 instances of increased disease activity were identified, only one major disease outbreak affecting eight contiguous local government areas was detected in summer/autumn 2002/2003. This outbreak contained 297 cases, 115 more than would be expected over this period. The factors important to this outbreak are unknown and require further investigation. Although the incidence rates for BFV disease are lower than Ross River virus disease, the most reported mosquito-borne disease in Australia, several factors indicate that this virus should be considered an important public health risk in Queensland. These include consistent endemic transmission, apparent underreporting of the disease, and the potential for outbreaks in major population centers.

New approaches to quantifying the spread of infection.

Recent major disease outbreaks, such as severe acute respiratory syndrome and foot-and-mouth disease in the UK, coupled with fears of emergence of human-to-human transmissible variants of avian influenza, have highlighted the importance of accurate quantification of disease threat when relatively few cases have occurred. Traditional approaches to mathematical modelling of infectious diseases deal most effectively with large outbreaks in large populations. The desire to elucidate the highly variable dynamics of disease spread amongst small numbers of individuals has fuelled the development of models that depend more directly on surveillance and contact-tracing data. This signals a move towards a closer interplay between epidemiological modelling, surveillance and disease-management strategies.

Mucosal vaccination delays or prevents prion infection via an oral route

In recent years major outbreaks of prion disease linked to oral exposure of the prion agent have occurred in animal and human populations. These disorders are associated with a conformational change of a normal protein, PrP C (prion protein cellular), to a toxic and infectious form, PrP Sc (prion protein scrapie). None of the prionoses currently have an effective treatment. A limited number of active immunization approaches have been shown to slightly prolong the incubation period of prion infection. Active immunization in wild-type animals is hampered by auto-tolerance to PrP and potential toxicity. Here we report that mucosal vaccination with an attenuated Salmonella vaccine strain expressing the mouse PrP, is effective at overcoming tolerance to PrP and leads to a significant delay or prevention of prion disease in mice later exposed orally to the 139A scrapie strain. This mucosal vaccine induced gut anti-PrP immunoglobulin (Ig)A and systemic anti-PrP IgG. No toxicity was evident with this vaccination approach. This promising finding suggests that mucosal vaccination may be a useful method for overcoming tolerance to PrP and preventing prion infection among animal and potentially human populations at risk.

Evidence in the Legionella pneumophila genome for exploitation of host cell functions and high genome plasticity.

Legionella pneumophila, the causative agent of Legionnaires' disease, replicates as an intracellular parasite of amoebae and persists in the environment as a free-living microbe. Here we have analyzed the complete genome sequences of L. pneumophila Paris (3,503,610 bp, 3,077 genes), an endemic strain that is predominant in France, and Lens (3,345,687 bp, 2,932 genes), an epidemic strain responsible for a major outbreak of disease in France. The L. pneumophila genomes show marked plasticity, with three different plasmids and with about 13% of the sequence differing between the two strains. Only strain Paris contains a type V secretion system, and its Lvh type IV secretion system is encoded by a 36-kb region that is either carried on a multicopy plasmid or integrated into the chromosome. Genetic mobility may enhance the versatility of L. pneumophila. Numerous genes encode eukaryotic-like proteins or motifs that are predicted to modulate host cell functions to the pathogen's advantage. The genome thus reflects the history and lifestyle of L. pneumophila, a human pathogen of macrophages that coevolved with fresh-water amoebae.

Modeling biological disturbances in LANDIS: a module description and demonstration using spruce budworm

Insects and diseases are common disturbance agents in forested ecosystems. Severe outbreaks can cause significant changes in tree species composition, age structure, and fuel conditions over broad areas. To investigate the role of biological disturbances in shaping forest landscapes over time, we constructed a new “biological disturbance agent” (BDA) module for a landscape-level forest succession and disturbance simulator, LANDIS. The BDA module is designed to simulate tree mortality following major outbreaks of insects and/or disease. Major outbreaks are defined as those significant enough to influence forest succession, fire disturbance, or harvest disturbance at landscape scales. Module design is flexible to accommodate a diversity of life history traits characterizing destructive insects and diseases, and more than one BDA can be simulated to examine their interactions. Five main elements control the probability of biological disturbance within the module: (1) local host dominance on a given site; (2) host value modifiers that reflect environmental conditions and recent disturbance history; (3) host dominance within a user-specified neighborhood; (4) the temporal outbreak pattern characteristic of the BDA, and (5) BDA dispersal in cases where the annual dispersal range of the BDA is small relative to the study area. In this paper, we describe the first four elements of the BDA module, and present the initial testing of the module on a variety of neutral landscape patterns, using Eastern spruce budworm as a test case. Our results are consistent with published successional patterns of spruce-fir and mixed forests affected by spruce budworm, but also highlight areas of uncertainty in the spatio-temporal patterns of budworm-caused tree mortality and biological disturbances in general. We suggest that the behavior of the module is consistent with the design and intended purpose of LANDIS as a probabilistic landscape-level simulator of forest disturbance and succession.

Venezuelan equine encephalitis emergence: enhanced vector infection from a single amino acid substitution in the envelope glycoprotein.

In 1993 and 1996, subtype IE Venezuelan equine encephalitis (VEE) virus caused epizootics in the Mexican states of Chiapas and Oaxaca. Previously, only subtype IAB and IC VEE virus strains had been associated with major outbreaks of equine and human disease. The IAB and IC epizootics are believed to emerge via adaptation of enzootic (sylvatic, equine-avirulent) strains for high titer equine viremia that results in efficient infection of mosquito vectors. However, experimental equine infections with subtype IE equine isolates from the Mexican outbreaks demonstrated neuro-virulence but little viremia, inconsistent with typical VEE emergence mechanisms. Therefore, we hypothesized that changes in the mosquito vector host range might have contributed to the Mexican emergence. To test this hypothesis, we evaluated the susceptibility of the most abundant mosquito in the deforested Pacific coastal locations of the VEE outbreaks and a proven epizootic vector, Ochlerotatus taeniorhynchus. The Mexican epizootic equine isolates exhibited significantly greater infectivity compared with closely related enzootic strains, supporting the hypothesis that adaptation to an efficient epizootic vector contributed to disease emergence. Reverse genetic studies implicated a Ser --> Asn substitution in the E2 envelope glycoprotein as the major determinant of the increased vector infectivity phenotype. Our findings underscore the capacity of RNA viruses to alter their vector host range through minor genetic changes, resulting in the potential for disease emergence.

Estimating vaccine efficacy from small outbreaks

SUMMARY Let Cv and CO denote the number of cases among vaccinated and unvaccinated individuals, respectively, and let v be the proportion of individuals vaccinated. The quantity e = 1 - (1 - v)Cv/(vCo) = 1 - (relative attack rate) is the most used estimator of the effectiveness of a vaccine to protect against infection. For a wide class of vaccine responses, a family of transmission models and three types of community settings, this paper investigates what e actually estimates. It does so under the assumption that the community is large and the vaccination coverage is adequate to prevent major outbreaks of the infectious disease, so that only data on minor outbreaks are available. For a com munity of homogeneous individuals who mix uniformly, it is found that e estimates a quantity with the interpretation of 1 - (mean susceptibility, per contact, of vaccinees relative to unvaccinated individuals). We provide a standard error for e in this setting. For a community with some heterogeneity e can be a very misleading estimator of the effectiveness of the vaccine. When individuals

The emerging animal health delivery system in the People's Republic of China.

Livestock production in the People's Republic of China has expanded at an unprecedented rate over the last decade and this trend is expected to continue into the foreseeable future. Government and private sector investment supports this growth, and the fact that small farmers are incorporating more animal husbandry into their work is expected to mitigate some of the concerns over recent World Trade Organization accession, particularly in the more precarious grain growing regions. Modernisation and intensification of the livestock industry in the People's Republic of China is subject to significant risks as regards both infectious and production-related diseases and within the framework of food safety and public health challenges. Although historically, the veterinary service system in the People's Republic of China has been successful in the eradication and control of major disease outbreaks, domestic and international market concerns are providing the catalyst for significant reforms in the animal health delivery system in the country. This paper provides an overview of the existing veterinary system in terms of the education and qualifications of veterinary personnel, delivery mechanisms, and future approaches to reforming the system in the context of a dynamic livestock industry in transition.

Emerging encephalitogenic viruses: lyssaviruses and henipaviruses transmitted by frugivorous bats.

Three newly recognized encephalitogenic zoonotic viruses spread from fruit bats of the genus Pteropus (order Chiroptera, suborder Megachiroptera) have been recognised over the past decade. These are: Hendra virus, formerly named equine morbillivirus, which was responsible for an outbreak of disease in horses and humans in Brisbane, Australia, in 1994; Australian bat lyssavirus, the cause of a severe acute encephalitis, in 1996; and Nipah virus, the cause of a major outbreak of encephalitis and pulmonary disease in domestic pigs and people in peninsula Malaysia in 1999. Hendra and Nipah viruses have been shown to be the first two members of a new genus, Henipavirus, in the family Paramyxoviridae, subfamily Paramyxovirinae, whereas Australian bat lyssavirus is closely related antigenically to classical rabies virus in the genus Lyssavirus, family Rhabdoviridae, although it can be distinguished on genetic grounds. Hendra and Nipah viruses have neurological and pneumonic tropisms. The first humans and equids with Hendra virus infections died from acute respiratory disease, whereas the second human patient died from an encephalitis. With Nipah virus, the predominant clinical syndrome in humans was encephalitic rather than respiratory, whereas in pigs, the infection was characterised by acute fever with respiratory involvement with or without neurological signs. Two human infections with Australian bat lyssavirus have been reported, the clinical signs of which were consistent with classical rabies infection and included a diffuse, non-suppurative encephalitis. Many important questions remain to be answered regarding modes of transmission, pathogenesis, and geographic range of these viruses.

Severe acute respiratory syndrome and the delivery of continuing medical education: Case study from Toronto

Severe acute respiratory syndrome (SARS) struck Toronto in the spring of 2003, causing many deaths, serious morbidity, forced quarantine of thousands of individuals, and the closure of all provincial hospitals for several weeks. Given the direction by public health authorities to cancel or postpone all continuing medical education (CME) courses, including those sponsored by the University of Toronto Faculty of Medicine, SARS has had a profound effect on the delivery of CME in Toronto and beyond. Case study design using existing documents and self-report. The immediate, specific response of the University of Toronto CME program to SARS is described for the period from March 2003 to September 2003. During major outbreaks of infectious disease, continuing education providers should maintain regular contact with public health authorities and learners, enact a rational process for postponing or canceling courses, and implement a disaster plan flexible enough to ensure the deliver, of education using technological advances.

Globalization and Disease: The Case of SARS

The purpose of this paper is to provide an assessment of the global economic impacts of severe acute respiratory syndrome (SARS) as well as to provide a more comprehensive approach to estimating the global consequences of major disease outbreaks. Our empirical estimates of the economic effects of the SARS epidemic are based on a global model called the G-Cubed (Asia Pacific) model. Most previous studies on the economic effects of epidemics focus on the disease-associated medical costs or forgone incomes resulting from disease-related morbidity and mortality, but the most significant real costs of SARS have been generated by changes in spending behavior by households and firms in affected countries. This study estimates the cost of the SARS outbreak by focusing on the impacts on consumption and investment behavior through changes in the cost and risk of doing business. Through increased economic interdependence, these changes in behavior have wide-ranging general equilibrium consequences for the world economy that can lead to economic losses well in excess of the traditional estimates of the cost of disease.

Occupational health in British agriculture.

If prostitution is the oldest profession, then agriculture is surely the oldest industry. It was the transition of man from hunter–gatherer to farmer that first enabled civilizations to develop and other industries to evolve. For thousands of years, the majority of the world’s population worked on the land, but nowadays most people live in cities, and the agricultural workforce in developed countries is shrinking. This has been possible because technological advances, particularly over the past 200 years, have made food production much more efficient. Mechanization has had an enormous impact, and other innovations, such as the use of agrochemicals and improved breeding of plants and animals, have also been important. Many people who, as a consequence of this, enjoy the luxury of a plentiful supply of food are now questioning the pace of change. Fears are widely voiced about threats to health and the environment from pesticides, genetically modified crops, the use of hormones in meat production and other aspects of modern agricultural practice. In Britain, the BSE epidemic, and more recently a major outbreak of foot and mouth disease in cattle, have further focused public attention on these issues. In response, the government has initiated a major review of farming and of the rural economy more widely [1]. Caught up in the middle of these developments are the farmers and their employees, who must continue to earn a living while all about them is changing or uncertain. As well as psychological stresses, they face a range of chemical, physical, biological and ergonomic hazards in the course of their work. And because of the way in which the industry is organized, with most of the workforce employed in small businesses, access to occupational health services is limited. Against this background, we have put together a series of papers reviewing various aspects of occupational health in farming. The focus is principally on agriculture in the UK, but much of the material will also be relevant to other countries.

Response of Italian elite subterranean clover genotypes to Fusarium avenaceum and Fusarium oxysporum under artificial conditions

Breeding programs of subterranean clover in southern Europe have traditionally set low priority on selection against major pathogens, in part because there have been no major disease outbreaks in this region. However, root-rot causing fungi, such as Fusarium spp., occur frequently on other crops and can therefore also represent a threat to clover. Thus, the breeding program carried out in Sardinia, Italy, took note of this disease. This study reports the results of 2 trials carried out in 2 consecutive years following artificial infestation with Fusarium spp. The first trial included 45 genotypes, of which 37 were Sardinian lines under advanced breeding and 8 were commercial varieties. To validate the variation observed in disease response, a subset of 27 genotypes was further evaluated in the second trial. In both trials, 3 pathogen treatments were applied, in addition to a control, uninoculated treatment - F. avenaceum, F. oxysporum, and an equal mixture of both fungi. One-month-old clover seedlings were scored in all treatments for shoot-growth vigour (1-9 scale), then excavated for scoring root-rot symptoms (1-5�scale), and finally weighed after oven drying. Analysis of variance tested differences among treatments, among genotypes, and between subsp. subterraneum and brachycalycinum of Trifolium subterraneum. On the common set of genotypes to both trials, a cluster analysis was applied using, as original variables, the average disease score across the 3 inoculated treatments in the 2 trials. Confirming previous evidence, F. avenaceum proved more pathogenic than F. oxysporum. The results suggested that high seedling vigour may play a role in limiting root-rot effects, and this may also contribute to the relatively better tolerance of subsp. brachycalycinum over subsp. subterraneum observed. Despite some inconsistency of response in the 2 trials both at the treatment and genotype level, some Sardinian genotypes demonstrated a consistent level of tolerance especially in relation to the performance of the commercial varieties tested. Among them were the lines `125 brachy C', `56 sub D', `22 brachy G', `56 sub B' (=Campeda), and `19 brachy E' (=Antas).

Administrative law and the public's health.

Today, public health regulation at all levels faces unprecedented challenges both at home and abroad. The September 11, 2001 attacks on New York and Washington, D.C., by the Al Qaeda terrorist network and the anthrax bioterrorism that followed shortly thereafter have put public health regulation at the forefront of homeland security. The anthrax scare, in particular, has greatly tested the American public health system, calling into question whether the United States and its component states and localities are prepared to handle a major outbreak of infectious disease, such as smallpox, in a future bioterrorist action. While the response of public health agencies was commendable, especially in light of the magnitude of the assaults, it is manifestly clear that the American public health system will be hard pressed to meet similar challenges that may lie ahead.The events of fall 2001 follow a period of major challenges for public health. The AIDS pandemic has killed millions of people throughout the globe, especially in Africa and other parts of the developing world.

Emerging Waterborne Infections: Contributing Factors, Agents, and Detection Tools

Because microorganisms are easily dispersed, display physiological diversity, and tolerate extreme conditions, they are ubiquitous and may contaminate and grow in water. The presence of waterborne enteric pathogens (bacteria, viruses, and protozoa) in domestic water supplies represents a potentially significant human health risk. Even though major outbreaks of waterborne disease are comparatively rare, there is substantial evidence that human enteric pathogens that are frequently present in domestic water supplies are responsible for low-level incidence of waterborne microbial disease. Although these diseases are rarely debilitating to healthy adults for more than a few hours to a few days, enteric pathogens can cause severe illness, even death, for young children, the elderly, or those with compromised immune systems. As the epidemiology of waterborne diseases is changing, there is a growing global public health concern about new and reemerging infectious diseases that are occurring through a complex interaction of social, economic, evolutionary, and ecological factors. New microbial pathogens have emerged, and some have spread worldwide. Alternative testing strategies for waterborne diseases should significantly improve the ability to detect and control the causative pathogenic agents. In this article, we provide an overview of the current state of knowledge of waterborne microbial pathogens, their detection, and the future of new methods in controlling these infectious agents.

Infections à protozoaires et environnement

Protozoan parasites present a dispersal phase allowing spreading in the environment. Transmissive stages can be found in water, soil and food, where they can survive during long periods of time. Such parasites represent a continous threat for human and animal health. Main protozoans parasites are Cryptosporidium spp., Giardia spp., Cyclospora sp., Toxoplasma sp. as well as amœba Entamœba spp., Acanthamœba spp. and Naegleria sp. All these pathogens can be responsable for major waterborne disease outbreaks. The density of parasite contamination in aquatic environment particularly surface water and waste water begins to focus attention. Detection methods, however, have to be improved in order to be able to produce data such as viability, infectiosity and typing of the parasite stages. That are essentiel to determine the significance of the presence of these waterborne pathogens for public health.

No end in sight for foot and mouth

Britain is still in the midst of a major outbreak of foot and mouth disease, the first since 1967. By the middle of April, >1300 cases had been confirmed and >1 million animals had been slaughtered. The disease was first confirmed in the north east of England on 22 February 2001. The infection appears to have spread from there via markets and dealers to many other parts of the country before the virus was detected. The epidemic is expected to last at least until June or July, and livestock movement restrictions and culling animals on infected farms are considered to be the most effective control measures. To keep track of the continually changing picture, the UK Ministry of Agriculture, Fisheries and Food has established a website at http://www.maff.gov.uk/animalh/diseases/fmd/. CK