Waterborne diseases

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Waterborne diseases
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Waterborne diseases can be spread via groundwater which is contaminated with fecal pathogens from pit latrines
Specialty Infectious disease

Waterborne diseases are conditions caused by pathogenic micro-organisms that are transmitted in water. Disease can be spread while bathing, washing or drinking water, or by eating food exposed to contaminated water. While diarrhea and vomiting are the most commonly reported symptoms of waterborne illness, other symptoms can include skin, ear, respiratory, or eye problems. [1]

Contents

Various forms of waterborne diarrheal disease are the most prominent examples, and affect children in developing countries most dramatically. According to the World Health Organization, waterborne diseases account for an estimated 3.6% of the total DALY (disability- adjusted life year) global burden of disease, and cause about 1.5 million human deaths annually. The World Health Organization estimates that 58% of that burden, or 842,000 deaths per year, is attributable to a lack of safe drinking water supply, sanitation and hygiene (summarized as WASH). [2]

World Health Organization Specialised agency of the United Nations

The World Health Organization (WHO) is a specialized agency of the United Nations that is concerned with international public health. It was established on 7 April 1948, and is headquartered in Geneva, Switzerland. The WHO is a member of the United Nations Development Group. Its predecessor, the Health Organisation, was an agency of the League of Nations.

Disease burden impact of a health problem as measured by financial cost, mortality, morbidity, or other indicators

Disease burden is the impact of a health problem as measured by financial cost, mortality, morbidity, or other indicators. It is often quantified in terms of quality-adjusted life years (QALYs) or disability-adjusted life years (DALYs), both of which quantify the number of years lost due to disease (YLDs). One DALY can be thought of as one year of healthy life lost, and the overall disease burden can be thought of as a measure of the gap between current health status and the ideal health status. According to an article published in The Lancet in June 2015, low back pain and major depressive disorder were among the top ten causes of YLDs and were the cause of more health loss than diabetes, chronic obstructive pulmonary disease, and asthma combined. The study based on data from 188 countries, considered to be the largest and most detailed analysis to quantify levels, patterns, and trends in ill health and disability, concluded that "the proportion of disability-adjusted life years due to YLDs increased globally from 21.1% in 1990 to 31.2% in 2013." The environmental burden of disease is defined as the number of DALYs that can be attributed to environmental factors. These measures allow for comparison of disease burdens, and have also been used to forecast the possible impacts of health interventions. By 2014 DALYs per head were "40% higher in low-income and middle-income regions."

Drinking water water safe for consumption

Drinking water, also known as potable water, is water that is safe to drink or to use for food preparation. The amount of drinking water required varies. It depends on physical activity, age, health issues, and environmental conditions. Americans, on average, drink one litre of water a day and 95% drink less than three litres per day. For those who work in a hot climate, up to 16 litres a day may be required. Water is essential for life.

The term waterborne disease is reserved largely for infections that predominantly are transmitted through contact with or consumption of infected water. Trivially, many infections may be transmitted by microbes or parasites that accidentally, possibly as a result of exceptional circumstances, have entered the water, but the fact that there might be an occasional freak infection need not mean that it is useful to categorise the resulting disease as "waterborne". Nor is it common practice to refer to diseases such as malaria as "waterborne" just because mosquitoes have aquatic phases in their life cycles, or because treating the water they inhabit happens to be an effective strategy in control of the mosquitoes that are the vectors.

Malaria mosquito-transmitted disease

Malaria is a mosquito-borne infectious disease affecting humans and other animals caused by single-celled microorganisms belonging to the Plasmodium group. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases it can cause yellow skin, seizures, coma, or death. Symptoms usually begin ten to fifteen days after being bitten by an infected mosquito. If not properly treated, people may have recurrences of the disease months later. In those who have recently survived an infection, reinfection usually causes milder symptoms. This partial resistance disappears over months to years if the person has no continuing exposure to malaria.

Mosquito family of insects

Mosquitoes are a group of about 3500 species of small insects that are a type of fly. Within that order they constitute the family Culicidae. The word "mosquito" is Spanish for "little fly". Mosquitoes have a slender segmented body, a pair of wings, three pairs of long hair-like legs, feathery antennae, and elongated mouthparts.

Vector (epidemiology) agent that carries and transmits an infectious pathogen into another living organism

In epidemiology, a disease vector is any agent who carries and transmits an infectious pathogen into another living organism; most agents regarded as vectors are organisms, such as intermediate parasites or microbes, but it could be an inanimate medium of infection such as dust particles.

Microorganisms causing diseases that characteristically are waterborne prominently include protozoa and bacteria, many of which are intestinal parasites, or invade the tissues or circulatory system through walls of the digestive tract. Various other waterborne diseases are caused by viruses. (In spite of philosophical difficulties associated with defining viruses as "organisms", it is practical and convenient to regard them as microorganisms in this connection.)

Microorganism microscopic living organism

A microorganism, or microbe, is a microscopic organism, which may exist in its single-celled form or in a colony of cells.

Protozoa Diverse motile unicellular heterotrophic eukaryotic organisms

Protozoa is an informal term for single-celled eukaryotes, either free-living or parasitic, which feed on organic matter such as other microorganisms or organic tissues and debris. Historically, the protozoa were regarded as "one-celled animals", because they often possess animal-like behaviors, such as motility and predation, and lack a cell wall, as found in plants and many algae. Although the traditional practice of grouping protozoa with animals is no longer considered valid, the term continues to be used in a loose way to identify single-celled organisms that can move independently and feed by heterotrophy.

Bacteria A domain of prokaryotes – single celled organisms without a nucleus

Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.

Yet other important classes of water-borne diseases are caused by metazoan parasites. Typical examples include certain Nematoda, that is to say "roundworms". As an example of water-borne Nematode infections, one important waterborne nematodal disease is Dracunculiasis. It is acquired by swallowing water in which certain copepoda occur that act as vectors for the Nematoda. Anyone swallowing a copepod that happens to be infected with Nematode larvae in the genus Dracunculus, becomes liable to infection. The larvae cause guinea worm disease. [3]

Animal kingdom of motile multicellular eukaryotic heterotrophic organisms

Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres (110 ft) and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal often refers only to non-human animals. The study of non-human animals is known as zoology.

Dracunculiasis Infection by the Guinea worm

Dracunculiasis, also called Guinea-worm disease (GWD), is a parasitic infection by the Guinea worm. A person becomes infected when they drink water that contains water fleas infected with guinea worm larvae. Initially there are no symptoms. About one year later, the female worm forms a painful blister in the skin, usually on a lower limb. Other symptoms at this time may include vomiting and dizziness. The worm then emerges from the skin over the course of a few weeks. During this time, it may be difficult to walk or work. It is very uncommon for the disease to cause death.

Copepod subclass of crustaceans

Copepods are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic, some are benthic, and some continental species may live in limnoterrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds, and puddles, damp moss, or water-filled recesses (phytotelmata) of plants such as bromeliads and pitcher plants. Many live underground in marine and freshwater caves, sinkholes, or stream beds. Copepods are sometimes used as biodiversity indicators.

Another class of waterborne metazoan pathogens are certain members of the Schistosomatidae, a family of blood flukes. They usually infect victims that make skin contact with the water. [3] Blood flukes are pathogens that cause Schistosomiasis of various forms, more or less seriously affecting hundreds of millions of people worldwide. [4]

Schistosomatidae family of worms

Schistosomatidae is a family of digenetic trematodes with complex parasitic life cycles. Immature developmental stages of schistosomes are found in molluscs and adults occur in vertebrates. The best studied group, the blood flukes of the genus Schistosoma, infect and cause disease in humans. Other genera which are infective to non-human vertebrates can cause mild rashes in humans.

Trematoda class of worms

Trematoda is a class within the phylum Platyhelminthes. It includes two groups of parasitic flatworms, known as flukes.

Schistosomiasis Human disease caused by parasitic worms called schistosomes

Schistosomiasis, also known as snail fever and bilharzia, is a disease caused by parasitic flatworms called schistosomes. The urinary tract or the intestines may be infected. Symptoms include abdominal pain, diarrhea, bloody stool, or blood in the urine. Those who have been infected for a long time may experience liver damage, kidney failure, infertility, or bladder cancer. In children, it may cause poor growth and learning difficulty.

Long before modern studies had established the germ theory of disease, or any advanced understanding of the nature of water as a vehicle for transmitting disease, traditional beliefs had cautioned against the consumption of water, rather favouring processed beverages such as beer, wine and tea. For example, in the camel caravans that crossed Central Asia along the Silk Road, the explorer Owen Lattimore noted, "The reason we drank so much tea was because of the bad water. Water alone, unboiled, is never drunk. There is a superstition that it causes blisters on the feet." [5]

Socioeconomic impact

Waterborne diseases can have a significant impact on the economy, locally as well as internationally. People who are infected by a waterborne disease are usually confronted with related costs and not seldom with a huge financial burden. This is especially the case in less developed countries. The financial losses are mostly caused by e.g. costs for medical treatment and medication, costs for transport, special food, and by the loss of manpower. Many families must even sell their land to pay for treatment in a proper hospital. On average, a family spends about 10% of the monthly households income per person infected. [6]

Infections by type of pathogen

Protozoa

Disease and TransmissionMicrobial AgentSources of Agent in Water SupplyGeneral Symptoms
Acanthamoeba keratitis (cleaning of contact lenses with contaminated water) Acanthamoeba spp. (A. castellanii and A. polyphaga)widely-distributed free-living amoebae found in many types of aquatic environments, including surface water, tap water, swimming pools, and contact lens solutionsEye pain, eye redness, blurred vision, sensitivity to light, sensation of something in the eye, and excessive tearing
Amoebiasis (hand-to-mouth)Protozoan ( Entamoeba histolytica ) (Cyst-like appearance) Sewage, non-treated drinking water, flies in water supply, saliva transfer(if the other person has the disease)Abdominal discomfort, fatigue, weight loss, diarrhea, bloating, fever
Cryptosporidiosis (oral)Protozoan ( Cryptosporidium parvum )Collects on water filters and membranes that cannot be disinfected, animal manure, seasonal runoff of water. Flu-like symptoms, watery diarrhea, loss of appetite, substantial loss of weight, bloating, increased gas, nausea
Cyclosporiasis Protozoan parasite ( Cyclospora cayetanensis ) Sewage, non-treated drinking water cramps, nausea, vomiting, muscle aches, fever, and fatigue
Giardiasis (fecal-oral) (hand-to-mouth)Protozoan ( Giardia lamblia ) Most common intestinal parasiteUntreated water, poor disinfection, pipe breaks, leaks, groundwater contamination, campgrounds where humans and wildlife use same source of water. Beavers and muskrats create ponds that act as reservoirs for Giardia.Diarrhea, abdominal discomfort, bloating, and flatulence
Microsporidiosis Protozoan phylum ( Microsporidia ), but closely related to fungi Encephalitozoon intestinalis has been detected in groundwater, the origin of drinking water [7] Diarrhea and wasting in immunocompromised individuals.
Naegleriasis (primary amebic meningoencephalitis [PAM]) (nasal)Protozoan ( Naegleria fowleri ) (Cyst-like appearance) Watersports, non-chlorinated water Headache, vomiting, confusion, loss of balance, light sensitivity, hallucinations, fatigue, weight loss, fever, and coma

Bacteria

Disease and TransmissionMicrobial AgentSources of Agent in Water SupplyGeneral Symptoms
Botulism Clostridium botulinum Bacteria can enter an open wound from contaminated water sources. Can enter the gastrointestinal tract through consumption of contaminated drinking water or (more commonly) foodDry mouth, blurred and/or double vision, difficulty swallowing, muscle weakness, difficulty breathing, slurred speech, vomiting and sometimes diarrhea. Death is usually caused by respiratory failure.
Campylobacteriosis Most commonly caused by Campylobacter jejuni Drinking water contaminated with feces Produces dysentery-like symptoms along with a high fever. Usually lasts 2–10 days.
Cholera Spread by the bacterium Vibrio cholerae Drinking water contaminated with the bacteriumIn severe forms it is known to be one of the most rapidly fatal illnesses known. Symptoms include very watery diarrhea, nausea, cramps, nosebleed, rapid pulse, vomiting, and hypovolemic shock (in severe cases), at which point death can occur in 12–18 hours.
E. coli Infection Certain strains of Escherichia coli (commonly E. coli)Water contaminated with the bacteriaMostly diarrhea. Can cause death in immunocompromised individuals, the very young, and the elderly due to dehydration from prolonged illness.
M. marinum infection Mycobacterium marinum Naturally occurs in water, most cases from exposure in swimming pools or more frequently aquariums; rare infection since it mostly infects immunocompromised individualsSymptoms include lesions typically located on the elbows, knees, and feet (from swimming pools) or lesions on the hands (aquariums). Lesions may be painless or painful.
Dysentery Caused by a number of species in the genera Shigella and Salmonella with the most common being Shigella dysenteriae Water contaminated with the bacteriumFrequent passage of feces with blood and/or mucus and in some cases vomiting of blood.
Legionellosis (two distinct forms: Legionnaires' disease and Pontiac fever)Caused by bacteria belonging to genus Legionella (90% of cases caused by Legionella pneumophila )Legionella is a very common organism that reproduces to high numbers in warm water; [9] but only causes severe disease when aerosolized. [10] Pontiac fever produces milder symptoms resembling acute influenza without pneumonia. Legionnaires' disease has severe symptoms such as fever, chills, pneumonia (with cough that sometimes produces sputum), ataxia, anorexia, muscle aches, malaise and occasionally diarrhea and vomiting
Leptospirosis Caused by bacterium of genus Leptospira Water contaminated by the animal urine carrying the bacteriaBegins with flu-like symptoms then resolves. The second phase then occurs involving meningitis, liver damage (causes jaundice), and renal failure
Otitis Externa (swimmer's ear)Caused by a number of bacterial and fungal species.Swimming in water contaminated by the responsible pathogens Ear canal swells, causing pain and tenderness to the touch
Salmonellosis Caused by many bacteria of genus Salmonella Drinking water contaminated with the bacteria. More common as a food borne illness.Symptoms include diarrhea, fever, vomiting, and abdominal cramps
Typhoid fever Salmonella typhi Ingestion of water contaminated with feces of an infected personCharacterized by sustained fever up to 40 °C (104 °F), profuse sweating; diarrhea may occur. Symptoms progress to delirium, and the spleen and liver enlarge if untreated. In this case it can last up to four weeks and cause death. Some people with typhoid fever develop a rash called "rose spots", small red spots on the abdomen and chest.
Vibrio Illness Vibrio vulnificus , Vibrio alginolyticus , and Vibrio parahaemolyticus Can enter wounds from contaminated water. Also acquired by drinking contaminated water or eating undercooked oysters.Symptoms include abdominal tenderness, agitation, bloody stools, chills, confusion, difficulty paying attention (attention deficit), delirium, fluctuating mood, hallucination, nosebleeds, severe fatigue, slow, sluggish, lethargic feeling, weakness.

Viruses

Disease and TransmissionViral AgentSources of Agent in Water SupplyGeneral Symptoms
SARS (Severe Acute Respiratory Syndrome) Coronavirus Manifests itself in improperly treated waterSymptoms include fever, myalgia, lethargy, gastrointestinal symptoms, cough, and sore throat
Hepatitis A Hepatitis A virus (HAV)Can manifest itself in water (and food)Symptoms are only acute (no chronic stage to the virus) and include Fatigue, fever, abdominal pain, nausea, diarrhea, weight loss, itching, jaundice and depression.
Hepatitis E (fecal-oral) Hepatitis E virus (HEV)Enters water through the feces of infected individualsSymptoms of acute hepatitis (liver disease), including fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain, jaundice, dark urine, clay-colored stool, and joint pain
Acute gastrointestinal illness [AGI] (fecal-oral; spread by food, water, person-to-person, and fomites) Norovirus Enters water through the feces of infected individuals Diarrhea, vomiting, nausea, stomach pain
Poliomyelitis (Polio) Poliovirus Enters water through the feces of infected individuals90-95% of patients show no symptoms, 4-8% have minor symptoms (comparatively) with delirium, headache, fever, and occasional seizures, and spastic paralysis, 1% have symptoms of non-paralytic aseptic meningitis. The rest have serious symptoms resulting in paralysis or death
Polyomavirus infection Two of Polyomavirus: JC virus and BK virus Very widespread, can manifest itself in water, ~80% of the population has antibodies to PolyomavirusBK virus produces a mild respiratory infection and can infect the kidneys of immunosuppressed transplant patients. JC virus infects the respiratory system, kidneys or can cause progressive multifocal leukoencephalopathy in the brain (which is fatal).

Algae

Disease and TransmissionMicrobial AgentSources of Agent in Water SupplyGeneral Symptoms
Desmodesmus infection desmodesmus armatusNaturally occurs in water. Can enter open wounds.Similar to fungal infection.

Parasitic worms

Disease and TransmissionAgentSources of Agent in Water SupplyGeneral Symptoms
Dracunculiasis [Guinea worm disease] (ingestion of contaminated water) Dracunculus medinensis Female worm emerges from host skin and releases larvae in waterSlight fever, itchy rash, nausea, vomiting, diarrhea, dizziness, followed by formation of painful blister (typically on lower body parts)

Surveillance

In the United States

The Waterborne Disease and Outbreak Surveillance System (WBDOSS) is the principal database used to identify the causative agents, deficiencies, water systems, and sources associated with waterborne disease and outbreaks in the United States. [16] Since 1971, the Centers for Disease Control and Prevention (CDC), the Council of State and Territorial Epidemiologists (CSTE), and the US Environmental Protection Agency (EPA) have maintained this surveillance system for collecting and reporting data on "waterborne disease and outbreaks associated with recreational water, drinking water, environmental, and undetermined exposures to water." [16] [17] "Data from WBDOSS have supported EPA efforts to develop drinking water regulations and have provided guidance for CDC’s recreational water activities." [16] [17]

WBDOSS relies on complete and accurate data from public health departments in individual states, territories, and other U.S. jurisdictions regarding waterborne disease and outbreak activity. [16] In 2009, reporting to the WBDOSS transitioned from a paper form to the electronic National Outbreak Reporting System (NORS). [16] Annual or biennial surveillance reports of the data collected by the WBDOSS have been published in CDC reports from 1971 to 1984; since 1985, surveillance data have been published in the Morbidity and Mortality Weekly Report (MMWR). [16]

See also

Related Research Articles

Zoonosis infectious disease that is transmitted between species (sometimes by a vector) from animals other than humans to humans or from humans to other animals

Zoonoses are infectious diseases that can be naturally transmitted between animals and humans.

Trichuriasis Infection by the parasitic worm Trichuris trichiura (whipworm)

Trichuriasis, also known as whipworm infection, is an infection by the parasitic worm Trichuris trichiura (whipworm). If infection is only with a few worms, there are often no symptoms. In those who are infected with many worms, there may be abdominal pain, tiredness and diarrhea. The diarrhea sometimes contains blood. Infections in children may cause poor intellectual and physical development. Low red blood cell levels may occur due to loss of blood.

<i>Norovirus</i> genus of viruses

Norovirus, sometimes referred to as the winter vomiting bug, is the most common cause of gastroenteritis. Infection is characterized by diarrhea, vomiting, and stomach pain. Blood is not usually present. Fever or headaches may also occur. This usually develops 12 to 48 hours after being exposed. Recovery typically occurs within 1 to 3 days. Complications may include dehydration.

Intestinal parasite infection Condition in which a parasite infects the gastro-intestinal tract of humans and other animals

An intestinal parasite infection is a condition in which a parasite infects the gastro-intestinal tract of humans and other animals. Such parasites can live anywhere in the body, but most prefer the intestinal wall.

Cryptosporidiosis Human disease

Cryptosporidiosis, also known as crypto, is a parasitic disease caused by Cryptosporidium, a genus of protozoan parasites in the phylum Apicomplexa. It affects the distal small intestine and can affect the respiratory tract in both immunocompetent and immunocompromised individuals, resulting in watery diarrhea with or without an unexplained cough. In immunosuppressed individuals, the symptoms are particularly severe and can be fatal. It is primarily spread through the fecal-oral route, often through contaminated water; recent evidence suggests that it can also be transmitted via fomites in respiratory secretions.

Giardiasis parasitic disease caused by Giardia lamblia

Giardiasis, popularly known as beaver fever, is a parasitic disease caused by Giardia lamblia. About 10% of those infected have no symptoms. When symptoms occur they may include diarrhea, abdominal pain, and weight loss. Vomiting, blood in the stool, and fever are less common. Symptoms usually begin 1 to 3 weeks after exposure and without treatment may last up to six weeks.

Helminthiasis Macroparasitic disease in which a part of the body is infected with parasitic worms

Helminthiasis, also known as worm infection, is any macroparasitic disease of humans and other animals in which a part of the body is infected with parasitic worms, known as helminths. There are numerous species of these parasites, which are broadly classified into tapeworms, flukes, and roundworms. They often live in the gastrointestinal tract of their hosts, but they may also burrow into other organs, where they induce physiological damage.

Hookworm infection Human disease caused by infection by intestinal parasites of the roundworm group

Hookworm infection is an infection by a type of intestinal parasite known as a hookworm. Initially, itching and a rash may occur at the site of infection. Those only affected by a few worms may show no symptoms. Those infected by many worms may experience abdominal pain, diarrhea, weight loss, and tiredness. The mental and physical development of children may be affected. Anemia may result.

Natural reservoir long-term host of the pathogen of an infectious disease

In infectious disease ecology and epidemiology, a natural reservoir, also known as a disease reservoir or a reservoir of infection, is the population of organisms or the specific environment in which an infectious pathogen naturally lives and reproduces, or upon which the pathogen primarily depends for its survival. A reservoir is usually a living host of a certain species, such as an animal or a plant, inside of which a pathogen survives, often without causing disease for the reservoir itself. By some definitions a reservoir may also be an environment external to an organism, such as a volume of contaminated air or water.

<i>Cryptosporidium</i> genus of apicomplexan parasitic alveolate

Cryptosporidium is a genus of apicomplexan parasitic alveolates that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves watery diarrhea with or without a persistent cough in both immunocompetent and immunodeficient humans.

Wilderness-acquired diarrhea is a variety of traveler's diarrhea in which backpackers and other outdoor enthusiasts are affected. Potential sources are contaminated food or water, or "hand-to-mouth", directly from another person who is infected. Cases generally resolve spontaneously, with or without treatment, and the cause is typically unknown. The National Outdoor Leadership School has recorded about one incident per 5,000 person-field days by following strict protocols on hygiene and water treatment. More limited, separate studies have presented highly varied estimated rates of affliction that range from 3 percent to 74 percent of wilderness visitors. One survey found that long-distance Appalachian Trail hikers reported diarrhea as their most common illness. Based on reviews of epidemiologic data and literature, some researchers believe that the risks have been over-stated and are poorly understood by the public. U.S. adults annually experience 99 million episodes of acute diarrhea in a population of about 318 million. A very small fraction of these cases results from infections acquired in the wilderness, and all infectious agents occur in both wilderness and non-wilderness settings.

Cyclosporiasis infection caused by Cyclospora cayetanensis

Cyclosporiasis is a disease caused by infection with Cyclospora cayetanensis, a pathogenic protozoan transmitted by feces or feces-contaminated food and water. Outbreaks have been reported due to contaminated fruits and vegetables. It is not spread from person to person, but can be a hazard for travelers as a cause of diarrhea.

The 1993 Milwaukee Cryptosporidiosis outbreak was a significant distribution of the Cryptosporidium protozoan in Milwaukee, Wisconsin, and the largest waterborne disease outbreak in documented United States history. The Howard Avenue Water Purification Plant was contaminated, and treated water showed turbidity levels well above normal. It was one of two water treatment plants for Milwaukee. The root cause of epidemic was never officially identified; initially it was suspected to be caused by the cattle genotype due to runoff from pastures. It was also thought that melting ice and snowmelt carrying Cryptosporidium may have entered the water treatment plants through Lake Michigan. MacKenzie et al. and the CDC showed that this outbreak was caused by Cryptosporidium oocysts that passed through the filtration system of one of the city's water-treatment plants, arising from a sewage treatment plant's outlet 2 miles upstream in Lake Michigan.

Neglected tropical diseases A diverse group of tropical infection diseases which are common in developing countries

Neglected tropical diseases (NTDs) are a diverse group of tropical infections which are common in low-income populations in developing regions of Africa, Asia, and the Americas. They are caused by a variety of pathogens such as viruses, bacteria, protozoa and helminths. These diseases are contrasted with the big three infectious diseases, which generally receive greater treatment and research funding. In sub-Saharan Africa, the effect of these diseases as a group is comparable to malaria and tuberculosis. NTD co-infection can also make HIV/AIDS and tuberculosis more deadly.

The discovery of disease-causing pathogens is an important activity in the field of medical science. Many viruses, bacteria, protozoa, fungi, helminthes and prions are identified as a confirmed or potential pathogen. In the United States, a Centers for Disease Control program, begun in 1995, identified over a hundred patients with life-threatening illnesses that were considered to be of an infectious cause, but that could not be linked to a known pathogen. The association of pathogens with disease can be a complex and controversial process, in some cases requiring decades or even centuries to achieve.

Airborne disease disease that is caused by pathogens and transmitted through the air

An airborne disease is any disease that is caused by pathogens that can be transmitted through the air. Such diseases include many of considerable importance both in human and veterinary medicine. The relevant pathogens may be viruses, bacteria, or fungi, and they may be spread through breathing, talking, coughing, sneezing, raising of dust, spraying of liquids, toilet flushing or any activities which generates aerosol particles or droplets. Human airborne diseases do not include conditions caused by air pollution such as Volatile Organic Compounds (VOCs), gases and any airborne particles, though their study and prevention may help inform the science of airborne disease transmission.

The National Outbreak Reporting System (NORS) is an electronic, web-accessible system designed to improve the quality, quantity, and availability of data for waterborne, foodborne, enteric person-to-person, and enteric zoonotic (animal-to-person) disease outbreaks in the United States.

The Waterborne Disease and Outbreak Surveillance System (WBDOSS) is a national surveillance system maintained by the U.S. Centers for Disease Control and Prevention (CDC). The WBDOSS receives data about waterborne disease outbreaks and single cases of waterborne diseases of public health importance in the United States and then disseminates information about these diseases, outbreaks, and their causes. WBDOSS was initiated in 1971 by CDC, the Council of State and Territorial Epidemiologists (CSTE), and the Environmental Protection Agency (EPA). Data are reported by public health departments in individual states, territories, and the Freely Associated States. Although initially designed to collect data about drinking water outbreaks in the United States, WBDOSS now includes outbreaks associated with recreational water, as well as outbreaks associated with water that is not intended for drinking (non-recreational) and water for which the intended use is unknown.

Viruses are a major cause of human waterborne and water-related diseases. Waterborne diseases are caused by water that is contaminated by human and animal urine and feces that contain pathogenic microorganisms. A subject can get infected through contact with or consumption of the contaminated water. Viruses affect all living organisms from single cellular plants, bacteria and animal to the highest forms of plants and animals including human beings. Viruses can interact with their host through several methods and mechanisms; some viruses can be host specific (HIV) and some can be less host specific (influenza) viruses. Different viruses can have different routes of transmission; for example, HIV is directly transferred by contaminated body fluids from an infected host into the tissue or bloodstream of a new host while influenza is airborne and transmitted through inhalation of contaminated air containing viral particles by a new host. Enteric viruses primarily infect the intestinal tract through ingestion of food and water contaminated with viruses of fecal origin. Some viruses can be transmitted through all three routes of transmission.

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Classification
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