Coronaviruses are spherical, lipid-containing, enveloped particles with tear-dropshaped surface projections or peplomers. The genome is one molecule of ssRNA and the virions characteristically contain three major structural protein classes. The antigenic relationships of coronaviruses present a complex pattern. The geographic distribution of many coronaviruses is worldwide. Biological vectors of coronaviruses have not been reported, and the natural hosts form the major reservoirs for further infection. Coronavirus particles contain three major protein classes, within which the polypeptides vary in number and molecular weight between species. The apparent size and shapes of coronaviruses can vary considerably. Coronavirus particles are spherical, although negatively stained air-dried particles are often pleomorphic. The morphology of coronavirus surface projections can vary considerably between different strains. The conventional structure on negative staining consists of tear-drop-shaped projections, although cone-shaped projections are also observed. In all these cases, the projections have the same length of about 20 nm. Other coronaviruses have short as well as 20-nm projections. Projections with blebs on thin stalks have been reported for other coronaviruses.
Rubella Epidemiology: Surveillance to Monitor and Evaluate Congenital Rubella Prevention StrategiesTo prevent cases of congenital rubella, there is a need of a comprehensive surveillance program to monitor immunity in the population and detect cases of both rubella and congenital rubella along with an understanding of the likely outcomes of different vaccination strategies. WHO developed guidelines for the surveillance of rubella and congenital. These recommend clinical surveillance of rubella and congenital rubella infection; serological surveillance to detect changes in the prevalence of rubella immunity in the population; and the recording of vaccine coverage. The age- and sex-specific incidence of rubella infection and the incidence of congenital rubella infection should be made available at the country level. Several research groups have modeled the transmission dynamics of rubella virus to assess the impact of different vaccine strategies and levels of vaccination uptake on age at infection, population seroprevalence and the number of pregnancies affected by rubella. Many studies focus on the dichotomy between schoolgirl vaccination programs, sometimes referred to as a selective vaccination strategy, and the vaccination of boys and girls in early life, i.e. a universal strategy.
Viruses in water are usually present in concentrations too low for detection by direct analysis. Virological investigation of water samples is always a multi-stage process involving concentration of viruses present followed by an appropriate detection procedure. There are several approaches to detection of viruses. Part or all of the concentrate may be inoculated into cell cultures to detect infectious cytopathogenic virus, and if this is done in a quantitative fashion the virus can be enumerated, the count being reported as plaque-forming units, the tissue culture infectious dose, or most probable number units. The virus may be isolated and identified from the cell cultures. Viruses that multiply without producing an identifiable cytopathic effect in culture may sometimes be detected by immunoperoxidase or immunofluorescence staining. The concentrate may also be analyzed by molecular biological procedures (usually polymerase chain reaction (PCR) or real-time-PCR). The problem then is that such techniques do not usually detect the infectious virus, and novel approaches have been made recently to meet this challenge.
Publisher Summary Understanding virus removal from drinkable water has been made more important because increased urbanization and burgeoning human populations result in increased wastes levels, more reuse of virus-contaminated wastewater and increasing land disposal of sewage sludges. This chapter reviews the current knowledge on reduction of the human pathogenic virus content in drinking water through treatment processes. Such reduction comprises two main components—the reduction in virus numbers by processes that remove particulates, and virus inactivations by physical or chemical treatments designed to damage microorganisms and eliminate their infectivity. More attention has been given to the removal of viruses than to their disinfection in this chapter. This is deliberate because these removal processes are normally at the beginning of the treatment train and effect the largest reduction in virus numbers. Disinfection is left to mop up the remainder of infectious virions that may have escaped the removal process.
Critical to the assessment of the risks from waterborne transmission of viruses is determining their occurrence and survival in the environment. There are number of factors controlling virus survival in aquatic environments, such as temperature, light, pH, salts, organic matter, suspended solids or sediments, and air–water interfaces. Most, if not all, viruses are released into the environment by excretion or secretion of bodily fluids or skin and hair. The viruses that infect the gastrointestinal tract are the most suited for transmission through the aquatic environment because they are released in large numbers in the stools of infected persons and have a prolonged survival in water. However, many respiratory viruses are excreted in the feces and many viruses are excreted in the urine. Respiratory adenoviruses have been shown to be transmitted by recreational waters; thus, there is the potential for viruses that may not primarily replicate in the intestinal tract to be transmitted by water.
Human enteroviruses (HEVs) can be found in natural and man-made environmental water bodies only as a consequence of contamination by human excreta. Survival of enteroviruses (EVs) in water depends on several factors but in general, examination of samples of water bodies for EVs can also be used as one approach in studies on EV epidemiology, defined as environmental surveillance. This is best exploited in the monitoring of the progress of the WHO-coordinated poliomyelitis eradication initiative (PEI). This chapter summarizes some key observations in this field and discusses possibilities and limitations of environmental surveillance of HEV infections. Systematic search for polioviruses in sewage samples, environmental surveillance for poliovirus circulation, is being used in several countries as a major approach to monitor potential reemergence of wild poliovirus circulation or to detect potential vaccine-derived polioviruses circulation. It also has a recognized role in the WHO strategy in the end-game of poliomyelitis eradication.
Enterically transmitted hepatitis represents the most common manifestation of acute hepatitis worldwide. Enteric hepatitis include two types: hepatitis A and hepatitis E. Hepatitis A infection may develop asymptomatically. This type of subclinical infection is most common among young children, while in older children and in the adulthood the infection usually proceeds with symptoms. The clinical course of hepatitis A is indistinguishable from that of other types of acute viral hepatitis. The clinical case definition for hepatitis A is an acute illness with moderate onset of symptoms (fever, malaise, anorexia, nausea, abdominal discomfort, and dark urine) and jaundice, and elevated serum bilirubin and aminotransferases levels later on. Hepatitis E is an infection with clinical and epidemiological features of acute hepatitis. The clinical presentation of hepatitis E is basically similar to that of hepatitis A, but cholestatic jaundice is more common. For detection and quantification of hepatitis A virus (HAV) immunological and, particularly, molecular techniques should be used. The availability of an increased number of Hepatitis E virus (HEV) sequences from different sources and geographical regions has enabled the design of specific oligonucleotide primers that match conserved regions of the HEV genome and allows the detection of HEV in acute phase sera, stools, and contaminated water and sewage. Inactivated HAV vaccines are available that provide long-lasting immunity against hepatitis A infection. Cross-reactive vaccines are also available that provides immunity against HEV.
Acquired immunodeficiency syndrome (AIDS) is caused by human immunodeficiency virus (HIV) that selectively kills cells of the immune system that are important to prevent disease due to infectious agents. AIDS was first reported in the United States in 1981 and has established a worldwide epidemic. There are more than 40 million people now living with HIV worldwide. There were 3 million HIV-related deaths in 2003, indicating that HIV has emerged as a major cause of death due to an infectious agent. There are two major subtypes of HIV, HIV-1, and HIV-2. This chapter discusses the pathogenesis that includes transmission and a brief discussion on HIV variants. Later, the chapter focuses on diagnostics and assay technology.
Hepatitis B virus (HBV) and hepatitis C virus (HCV) are noncytopathic viruses that cause acute and chronic liver diseases. Infection by HBV and HCV represents a major health problem as it is estimated that 500 million people worldwide are persistently infected by these viruses. Although the biology of HBV and HCV is well known, there are still critical steps in their viral life cycle, such as the mechanisms by which these viruses enter into the hepatocytes that are not well understood. Serological markers are key elements for the diagnosis of HBV and HCV infections. Nowadays, highly specific and sensitive assays are commercially available for this purpose, including tests for the detection of HBV and HCV genomes in serum and plasma samples.
Publisher Summary Every laboratory, including those that undertake research on surveillance or monitoring of human viruses in water should work according to a defined quality system, which sets out the management structure of the laboratory, the laboratory test and technological processes, equipment suitability, and staff competency thereby optimizing the production of reliable results. A quality manual should be maintained that documents the objectives of the quality system and how they are implemented. The manual describes all the documents that the laboratory should use and arrangements for internal and external quality assurance. Additionally, monitoring of water matrices can serve many purposes and is often an aspect of formal national regulation. The regular and continuing sampling of a body of water provides data, which is the basis of the action, gives confidence in treatment and can form the basis for predictive models of risk to public health. WHO has maximized the protection of public health through the provision of safe drinking and recreational water as a basic strategy. All aspects of the water environment should be assessed and viewed as a continuous process of which each aspect needs reviewing and action. The quality of drinking water is ensured through the framework of water safety plans, which are a means to address every aspect of the water supply chain from catchment to consumer using risk assessment and then risk management.
Surveillance is a fundamental tool for public health, producing information to guide actions. Modern surveillance tends to follow health measures such as the incidence of a disease or syndrome or even the occurrence of health-related behaviors. There are many reasons for conducting surveillance, and the data collected and the approach taken to analyzing those data are both influenced by the overall goal of a surveillance system. Surveillance systems aims mainly at detection also provide information that may be useful for other purposes. The goal of detecting an outbreak of a newly emerging virus, places specific demands on the type of data collected and the types of analysis performed. All approaches to surveillance share some common principles. While some of the underlying methods used in public health surveillance have evolved considerably in recent years, the general approach to surveillance has remained relatively constant. At a fundamental level, surveillance aims to (1) identify individual cases, (2) detect population patterns in identified cases, and then (3) convey information to decision-makers about population health patterns.
Publisher Summary Japanese encephalitis (JE) virus (JEV) is the major mosquito-borne encephalitic flavivirus of rural eastern, southeastern and southern Asia. The JE serological group comprises eight antigenically related virus species and two strains or subtypes, with members found on all continents except Antarctica. The viruses are cacipacore virus (CPCV), JEV, koutango virus (KOUV), Murray Valley encephalitis virus (MVEV), Saint Louis encephalitis virus (SLEV), Usutu virus (USUV), WNV, and Yaounde virus (YAOV), with Alfuy virus (ALFV) and Kunjin virus (KUNV) being subtypes of MVEV and WNV, respectively. JEV exists as a single serotype, but antigenic variation has been recognized using polyclonal and monoclonal antibodies. Furthermore, a correlation between genetic variation and JEV activity has been observed, with isolates from northern temperate areas where JE occurs as summer epidemics predominantly caused by genotypes 1 and 3, whereas endemic strains found in tropical equatorial regions have been associated with genotypes 2 and 4. However, several exceptions to this pattern are also demonstrated.
The detection of viruses in water and other environmental samples constitutes special challenges. The standard method of detection of viral pathogens in environmental samples uses assays in mammalian cell culture. The infected cell cultures undergo observable morphological changes called cytopathogenic effects (CPEs) that are used for the detection of viruses. Even though many viruses are culturable in several cell lines and are thus detectable by the development of CPEs in cell culture, there are several viruses, like enteric waterborne adenoviruses types 40 and 41, which are difficult to culture and do not produce clear and consistent CPE. Other viruses, like waterborne caliciviruses, have not yet been successfully grown in cell cultures. Conventional cell culture assays for the detection of viruses in environmental samples have limited sensitivity and can be labor-intensive and timeconsuming. Two advances, the PCR and microarrays, have spurred the study of viruses and should be further applied to the field of environmental virology. The ability of both DNA viruses and RNA viruses to rapidly evolve means new and emerging viral pathogens will need to be addressed. Pathogen discovery and characterization, occurrence in the environment, exposure pathways, and health outcomes via environmental exposure need to be addressed. This will likely follow a new microbial risk framework that will require focused research on some important properties of viral disease transmission. The future will require models that examine community risks and provide explicit links between the models currently under development for environmental exposure and infectious disease.
Chagas disease, a antropozoonosis caused by the protozoan Trypanosoma cruzi, is one of the main parasitic diseases to threaten public health in the world. More than any other parasitic disease, Chagas disease is closely related to social and economic development. T. cruzi infection may be acquired through the triatomid insect vector, blood transfusion, and the transplacental route causing congenital Chagas disease. The success in the control of vector-transmitted Chagas'disease and screening programs in blood banks has uncovered the public health relevance of congenital transmission, which has been gradually emerging in vector-free suburban areas and non-endemic cities, contributing to the urbanization of the infection. It has been estimated that congenital transmission is responsible for 8000-16,000 annual cases in the endemic countries of America. It is a consensus that congenital Chagas disease will be a pressing public health concern until the pool of infected women of childbearing age decreases to insignificant levels, which may happen only 30 years onwards, at least in the Southern Cone countries.Congenital transmission may occur at any time of pregnancy, in successive gestations and may affect twins. The infection may produce pathology in the growing foetus. The consequences on the newborn are variable, ranging from asymptomatic to severe clinical manifestations. The prevalence of T. cruzi infection in women of childbearing age, congenital transmission rates, clinical forms of disease, and mortality vary largely according to the geographical areas under study. Host conditions, such as the immunological, genetic, and nutritional status of the mothers, age, obstetrical history, and maternal stage of the disease, as well as parasite strains, histotropism and maternal parasitaemia may account as risk factors for pregnancy outcome and incidence of congenital Chagas disease. Congenital transmission cannot be prevented, but early diagnosis of the newborn enables prompt treatment, achieving cure rates close to 100% and thus avoiding progression to chronic Chagas disease.In this chapter, epidemiological, clinical, and inmunological aspects as well as mechanisms of transmission, host and parasitic risk factors are described and discussed. Finally, consensus recommendations of strategies for diagnosis and treatment of congenital Chagas disease are presented in detail.
Many aspects related to water quality control surrogate indicators are still needed because at present techniques do not allow for the moment to distinguish whether the detected viruses are infectious or not, without introducing additional steps that impair the efficiency of the detection method. Bacterial groups that include Escherichia coli, Enterococcus spp., and Clostridium perfringens have been the conventional indicators. More recently, with the advent of methods that allow their direct detection, these bacterial species or genera have been used as indicators of water pollution. Recently, human enteric virus and bacteriophages of enteric bacteria have both been advocated as potential viral indicators. After the advent of the genomic techniques, the genome of viruses excreted by humans had also been proposed as potential viral indicator. Somatic coliphages, F-specific RNA bacteriophages and bacteriophages infecting Bacteroides fragilis have so far been advocated as potential model microorganisms for various aspects of water quality control.
Publisher Summary Several virus diseases that emerged in the last two decades of the 20 th century have now become entrenched in human populations worldwide, and unfortunately, the methodological advances that led to their detection have not been matched by similar advances to prevent and control them. Attempts to develop vaccines for these have in most cases eluded all efforts. There have been improvements in antiviral therapy, but these are not effective in all cases, often resulting in control rather than cure of the disease, and they remain out of the reach of many patients in poor and underdeveloped countries. This chapter discusses some viruses like human immunodeficiency virus, type 1 (HIV-1), human T-lymphotropic viruses, hepatitis C virus, and variant Creutzfeldt-Jakob disease (vCJD).
Nipah and Hendra viruses are two zoonotic paramyxoviruses with an ability to cause fatal encephalitic and respiratory diseases in humans. Nipah and Hendra viruses are negative sense, single-stranded RNA viruses in the Paramyxoviridae family, subfamily Paramyxovirinae. They are categorized in the recently named genus Henipavirus, one of five genera in the subfamily (the others are Respirovirus, Morbillovirus, Avulavirus, and Rubulavirus). Other human pathogenic viruses exist in these other genera, such as measles, mumps, and parainfluenza viruses; Nipah and Hendra viruses, in the genus Henipavirus, and Menangle virus, in the genus Rubalavirus, are unique in that they are zoonotic and are viruses that have recently emerged in humans. A similarity exists between the epidemiology of each of these two viruses, such as the Pteropus fruit bat as the natural host for both viruses. For both Hendra and Nipah viruses, it is presumed that horses and pigs that have acted as an intermediary host to humans had been infected by indirect contact with pteropid bats endemic in these regions, although this has not been experimentally proven.
Herpes simplex virus (HSV) infection in newborns is an important cause of death and permanent neurodevelopmental disability among young children. Neonatal HSV infections can be categorized as 1) mucocutaneous (skin-eyes-mouth), 2) disseminated, or 3) encephalitic. In addition, congenital HSV infection, a distinct clinical syndrome, accounts for approximately 5% of HSV infections identified in the neonatal period. Polymerase chain reaction greatly enhances the clinician's ability to diagnosis HSV infections, but as many as 25% of infants with neonatal HSV encephalitis have negative polymerase chain reaction studies of cerebrospinal fluid. Infants with proven or suspected HSV infections should receive acyclovir 60 mg/kg/day divided every 8 hours for 14 days if disease is restricted to the skin, eyes, or mucous membranes and for 21 days if the infant has disseminated infection or encephalitis. The benefit of long-term suppression therapy after completion of the initial treatment regimen has not been established definitively. Despite therapy with acyclovir, the best available anti-HSV drug, a substantial number of HSV-infected infants with disseminated infections or encephalitis die or have long-term neurodevelopmental sequelae.
