What are the primary causes of Hepatitis A?

Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus (HAV). It primarily spreads through the ingestion of contaminated food or water, often due to improper hygiene practices. The virus is excreted in the feces of an infected person, and transmission occurs when an individual consumes food or water that has been tainted by the virus. This contamination is particularly common in areas with inadequate sanitation and limited access to clean water.

Another significant route of hepatitis A transmission is direct person-to-person contact. This can occur through close interactions such as living in the same household as an infected individual, caring for an infected person, or engaging in sexual activities, particularly oral-anal contact. The virus can also survive on surfaces and objects for extended periods, increasing the risk of indirect transmission when contaminated hands come into contact with the mouth.

Hepatitis A outbreaks are more prevalent in regions with poor sanitation, overcrowded living conditions, and insufficient public health infrastructure. Developing countries, particularly those in Africa, South Asia, and parts of Latin America, experience higher rates of infection due to limited access to clean drinking water and inadequate waste disposal systems. Even in developed nations, sporadic outbreaks have been linked to contaminated food, such as fresh produce, frozen berries, and undercooked shellfish harvested from polluted waters.

Symptoms of hepatitis A typically appear two to six weeks after exposure and can range from mild to severe. Common symptoms include fatigue, nausea, vomiting, abdominal pain, loss of appetite, jaundice (yellowing of the skin and eyes), and dark urine. While the infection is generally self-limiting and does not lead to chronic liver disease, severe cases can result in acute liver failure, particularly among older adults and individuals with pre-existing liver conditions.

Prevention is the most effective strategy against hepatitis A. The hepatitis A vaccine provides long-term immunity and is recommended for children, travelers to high-risk areas, individuals with chronic liver disease, and those at increased risk due to occupational or lifestyle factors. Practicing good hygiene, such as thorough handwashing with soap and water after using the restroom and before handling food, is crucial in reducing transmission. Ensuring safe food handling practices, consuming properly cooked meals, and drinking clean water can further minimize the risk.

In conclusion, hepatitis A remains a significant public health concern, particularly in areas with poor sanitation. The primary causes of infection include ingestion of contaminated food or water, direct contact with infected individuals, and environmental exposure. Vaccination, hygiene, and improved sanitation are key measures in preventing the spread of hepatitis A and reducing its global burden.
What are the primary causes of Hepatitis A?

E. coli: Balancing Beneficial Roles and Public Health Risks

Escherichia coli (E. coli) is a bacterium naturally found in the intestines of humans and animals. Most strains are harmless and even beneficial, aiding in digestion and nutrient absorption. However, certain pathogenic strains can cause significant illness, posing public health challenges worldwide.

Symptoms of E. coli infections depend on the strain and site of infection. Common signs include diarrhea, ranging from mild and watery to severe and bloody, accompanied by stomach cramps, pain, and tenderness. Some individuals also experience nausea, vomiting, loss of appetite, and low-grade fever. Severe infections, particularly those caused by strains like E. coli O157:H7, can lead to hemolytic uremic syndrome (HUS), a life-threatening condition marked by kidney failure, low red blood cell counts, and potential neurological complications.

Transmission primarily occurs through ingestion of contaminated food or water. High-risk sources include undercooked ground beef, unpasteurized dairy products, raw vegetables, and fruits exposed to contaminated water. Cross-contamination in kitchens and improper hygiene, such as insufficient handwashing after using the restroom or handling animals, also contribute to the spread of E. coli.

Preventing E. coli infections requires rigorous hygiene and food safety measures. Washing hands with soap and water after using the restroom, handling raw foods, or interacting with animals is essential. Cooking ground beef to an internal temperature of at least 160°F (71°C), avoiding unpasteurized products, and thoroughly washing fruits and vegetables can significantly reduce risks. In recent years, advancements in food safety protocols and public awareness campaigns have contributed to a decline in foodborne outbreaks in some regions, but challenges remain, especially in areas with limited access to clean water and sanitation.

If an E. coli infection is suspected, prompt medical attention is crucial. While mild cases often resolve without treatment, severe cases require careful management. Diagnostic tests, such as stool cultures, help identify the strain and guide treatment. Antibiotics are generally avoided for strains like E. coli O157:H7, as they can worsen complications. Instead, supportive care, including hydration and electrolyte balance, is emphasized.

E. coli infections underscore the importance of global efforts to improve sanitation, ensure food safety, and promote health education. By adopting preventative measures and responding swiftly to outbreaks, we can mitigate the risks associated with this bacterium and protect public health.
E. coli: Balancing Beneficial Roles and Public Health Risks

Understanding Campylobacter Enteritis: A Global Foodborne Threat

Campylobacter enteritis, caused by Campylobacter species—primarily Campylobacter jejuni and Campylobacter coli—is among the most prevalent bacterial infections worldwide. This foodborne illness impacts millions annually, particularly in regions with less stringent food safety regulations. The primary sources of infection include undercooked poultry, unpasteurized milk, untreated water, and cross-contamination during food preparation. Additionally, contact with infected animals or their environments can transmit the bacteria.

Symptoms typically manifest two to five days after exposure and include diarrhea (frequently bloody), abdominal cramping, fever, nausea, and vomiting. The illness usually resolves within a week, but symptoms may linger in some cases. Severe infections can lead to complications such as dehydration, sepsis, or even post-infectious conditions like Guillain-Barré syndrome, a rare neurological disorder. Vulnerable populations, including young children, older adults, and immunocompromised individuals, are at higher risk of severe outcomes.

The burden of Campylobacter enteritis varies globally, with developing nations bearing a disproportionate share due to poor sanitation and limited access to safe water. In developed countries, outbreaks often occur through mishandled food, particularly poultry, which can harbor Campylobacter on up to 80% of raw products. Recent studies highlight the role of antibiotic-resistant strains, complicating treatment options and posing a growing public health challenge.

Effective prevention hinges on robust food safety practices. These include thoroughly cooking poultry to an internal temperature of 165°F (74°C), avoiding raw or unpasteurized milk, and implementing stringent kitchen hygiene to prevent cross-contamination. Proper handwashing after handling raw meat, interacting with animals, or using the restroom is equally critical. On a broader scale, interventions such as improved agricultural practices, vaccination of poultry, and better monitoring of water quality can help mitigate risks.

Public awareness campaigns and education on foodborne diseases play a crucial role in empowering individuals to adopt safer practices. Governments and global health organizations must continue efforts to enhance surveillance, research, and the development of interventions to combat Campylobacter and other foodborne pathogens.

In summary, Campylobacter enteritis remains a significant global health issue. Through collective efforts in food safety, hygiene, and education, the incidence of this disease can be substantially reduced, safeguarding public health and preventing complications associated with this pervasive infection.
Understanding Campylobacter Enteritis: A Global Foodborne Threat

Scombroid Fish Poisoning: Causes, Symptoms, and Prevention

Scombroid fish poisoning, also known as histamine fish poisoning, is a foodborne illness resulting from the consumption of fish containing high histamine levels. This condition arises from improper storage or handling of fish, allowing bacterial growth to convert the naturally occurring amino acid histidine into histamine. While histamine is generally harmless in small amounts, excessive levels can lead to toxic effects. Commonly implicated fish include tuna, mackerel, mahi-mahi, sardines, anchovies, herring, bluefish, amberjack, and marlin. These species are particularly susceptible due to their high histidine content.

Symptoms and Diagnosis
Symptoms typically appear within 10 to 90 minutes after consuming contaminated fish and often mimic an allergic reaction. Initial signs include facial flushing, sweating, a metallic or peppery taste in the mouth, headache, and dizziness. These can escalate to more severe symptoms such as rash, hives, abdominal cramps, vomiting, diarrhea, and, in rare cases, respiratory distress or arrhythmias.

Diagnosis is clinical, relying on symptom presentation and a history of fish consumption. Laboratory tests may confirm elevated histamine levels in leftover fish, but such testing is not routine.

Treatment and Prognosis
Treatment primarily involves administering antihistamines like diphenhydramine or ranitidine to manage symptoms. Severe cases, though rare, may require epinephrine for respiratory or cardiovascular complications. Fortunately, scombroid poisoning is typically self-limiting, with most symptoms resolving within 24 hours without long-term effects.

Prevention and Global Perspective
Preventing scombroid poisoning hinges on proper handling and refrigeration of fish immediately after catch. Fish should be stored at temperatures below 4°C (39°F) to inhibit bacterial growth. Regulatory agencies, such as the U.S. FDA, recommend strict monitoring of the cold chain during transport and storage to reduce risks.

Scombroid poisoning remains a global concern, particularly in regions with warm climates where cold storage challenges persist. Awareness among consumers and food industry professionals is vital. Advances in rapid testing methods for histamine in fish may further enhance prevention efforts, safeguarding public health.
Scombroid Fish Poisoning: Causes, Symptoms, and Prevention

Understanding and Preventing Brucellosis: A Global Health Concern

Brucellosis, caused by bacteria from the Brucella genus, is a zoonotic disease primarily affecting livestock such as cattle, goats, sheep, and pigs. Its public health significance lies in its ability to cross species barriers and infect humans, posing risks especially in regions with inadequate veterinary and food safety systems.

Modes of Transmission
The most common source of brucellosis in humans is the consumption of unpasteurized dairy products—milk, cheese, and yogurt—produced from infected animals. Brucella bacteria can persist in these products, especially in regions where pasteurization is not widely practiced. Handling raw meat from infected animals without proper precautions can also result in bacterial transmission.

Occupational exposure is another major route of infection. Farmers, veterinarians, slaughterhouse workers, and laboratory personnel are at heightened risk. The bacteria can enter through skin abrasions, mucous membranes, or conjunctiva when handling infected tissues or animal fluids. For example, animal birthing materials, particularly from goats and sheep, are highly infectious.

Inhalation of airborne bacteria, a risk in laboratories or livestock facilities, is an emerging concern. Although rare, human-to-human transmission via blood transfusion, organ transplantation, or breastfeeding underscores the need for vigilance in healthcare settings.

Symptoms and Impact
In humans, brucellosis manifests as a febrile illness often accompanied by joint pain, fatigue, and sweats. Chronic forms can result in organ inflammation, arthritis, and neurological complications, severely impacting quality of life. Economically, it burdens livestock industries by reducing productivity through miscarriages, infertility, and reduced milk yields.

Prevention Strategies
Mitigation hinges on a multi-pronged approach. Vaccinating livestock is vital to curtailing animal reservoirs of the disease. Proper pasteurization of dairy products is an effective safeguard for consumers. Adherence to occupational safety measures, such as wearing protective gear and employing proper sanitation, minimizes risks for high-exposure groups. In laboratories, biosafety level-3 containment protocols are essential when handling Brucella cultures.

Efforts to control brucellosis must prioritize public awareness, food safety infrastructure, and stringent animal health programs. Global collaboration is essential to combat this often-overlooked disease, particularly in endemic regions across Africa, Asia, and the Mediterranean.
Understanding and Preventing Brucellosis: A Global Health Concern

Understanding Norovirus: Symptoms, Spread, and Prevention

Norovirus infection is a highly contagious illness caused by a group of viruses known as noroviruses. These viruses are notorious for causing gastroenteritis, an inflammation of the stomach and intestines, which leads to symptoms such as severe vomiting, diarrhea, nausea, and stomach cramps. The illness is often mistakenly referred to as the “stomach flu,” although it is unrelated to influenza. While influenza primarily affects the respiratory system, norovirus targets the digestive system, making the two conditions distinct in their nature and transmission routes.

Norovirus is known for its rapid spread, particularly in environments where people are in close proximity. The virus is highly resilient and can survive on surfaces for days, making it easily transmissible through contaminated food, water, or surfaces. People can also become infected by having direct contact with an infected individual. Closed and crowded environments, such as hospitals, nursing homes, schools, and cruise ships, are especially susceptible to outbreaks due to the ease with which the virus can spread in these settings. This contributes to the high prevalence of norovirus infections during certain times of the year, particularly in colder months when people tend to congregate indoors.

Once exposed to norovirus, symptoms usually develop within 12 to 48 hours. The illness typically lasts for one to three days, but during that time, it can cause significant discomfort and lead to complications like dehydration. This is especially concerning for vulnerable groups, including young children, the elderly, and individuals with weakened immune systems. In severe cases, dehydration from prolonged vomiting and diarrhea may require medical attention to restore fluid and electrolyte balance.

There is no specific antiviral treatment for norovirus. Instead, the primary management strategy focuses on relieving symptoms, staying hydrated, and resting. Preventive measures play a crucial role in controlling its spread. These include frequent hand washing, especially after using the bathroom or before handling food, thoroughly cleaning and cooking food, and disinfecting surfaces that may be contaminated. Although the illness is short-lived, its high contagion rate and potential severity highlight the importance of prevention and hygiene to limit outbreaks.
Understanding Norovirus: Symptoms, Spread, and Prevention

How Do I Know if I Have Salmonellosis?

Salmonellosis is a type of foodborne illness caused by the bacteria Salmonella. Knowing the symptoms is important for identifying whether you may be infected. Common symptoms include nausea, vomiting, stomach cramps, and diarrhea. Diarrhea, in some cases, can be bloody, which may indicate a more severe infection.

In addition to gastrointestinal issues, salmonellosis can also lead to other symptoms like headaches and fevers. A fever can occur as the body's immune system tries to fight off the bacterial infection. Headaches may accompany dehydration caused by frequent vomiting and diarrhea, both of which deplete the body of necessary fluids and electrolytes.

The symptoms of salmonellosis typically appear six hours to six days after consuming contaminated food or water. However, it is essential to remember that these symptoms can mimic other illnesses, such as viral gastroenteritis or food poisoning from other bacteria. For this reason, it’s important not to jump to conclusions based on symptoms alone. Other conditions like norovirus, E. coli infections, or even influenza can cause similar gastrointestinal symptoms. Therefore, if you suspect you have salmonellosis, it's crucial to inform a parent or guardian and seek medical advice.

A healthcare provider will likely recommend diagnostic tests to confirm whether you have salmonellosis. A stool sample is the most common way to test for Salmonella bacteria. This test helps distinguish salmonellosis from other infections that cause similar symptoms. In some cases, blood tests may be necessary if the infection has spread beyond the intestines.

It’s also vital to seek medical attention if symptoms are severe, such as prolonged vomiting or diarrhea, dehydration, or if the individual is in a high-risk group like young children, the elderly, or people with weakened immune systems. Early diagnosis and treatment can help prevent complications and speed up recovery.
How Do I Know if I Have Salmonellosis?

Recognizing and Managing Salmonellosis Symptoms

Salmonellosis is a bacterial infection caused by Salmonella, often contracted through contaminated food or water. Recognizing the symptoms early is crucial for proper treatment. Individuals with salmonellosis may experience nausea, vomiting, and painful stomach cramps, usually within 6 to 72 hours after exposure. Diarrhea, which can sometimes be bloody, is a common symptom and can lead to dehydration if not properly managed.

In addition to gastrointestinal symptoms, people with salmonellosis may also develop a headache and fever. These symptoms can last anywhere from four to seven days. It's important to note that these signs can mimic other illnesses, such as norovirus or certain types of food poisoning, making it difficult to self-diagnose.

If you suspect you have salmonellosis, it is essential to consult a healthcare provider. A doctor can confirm the diagnosis through stool tests and recommend appropriate treatment, which may include hydration and, in severe cases, antibiotics. Seeking medical advice is particularly important for vulnerable groups like young children, the elderly, and those with weakened immune systems, as they are at higher risk for severe complications. Early diagnosis and treatment are key to a swift recovery.
Recognizing and Managing Salmonellosis Symptoms

Understanding the Threat of Listeria monocytogenes

Listeria monocytogenes, a bacterium with deadly implications, poses a significant risk to public health. This organism is not to be underestimated, as it can lead to severe conditions such as encephalitis, meningitis, blood-borne infections, and ultimately, death. Its potency is particularly alarming for vulnerable populations, including pregnant women, newborns, the elderly, and individuals with weakened immune systems. Shockingly, Listeria accounts for approximately 28% of fatalities attributed to foodborne illnesses.

What makes Listeria monocytogenes especially menacing is its remarkable resilience in adverse conditions. Unlike many bacteria, it can endure acidic environments, high levels of nitrites and salt, and even survive in refrigerated temperatures. Consequently, it proliferates in various food sources, with raw (unpasteurized) milk, soft-ripened cheeses like Brie, and ready-to-eat meats such as hot dogs and pâté being common breeding grounds. Moreover, its reach extends to raw and smoked fish, poultry, fresh produce, and even ice cream.

The insidious nature of listeriosis, the infection caused by Listeria, adds to its danger. Symptoms initially manifest as seemingly benign, including headaches, low-grade fevers, muscle aches, nausea, and vomiting. Regrettably, these signs often mimic those of viral illnesses, leading to misdiagnosis and delayed treatment. Such delays offer Listeria the opportunity to progress unchecked. Furthermore, symptoms may not surface until anywhere from 3 to 70 days after exposure, further complicating detection and intervention.

Treating Listeria infections demands a proactive approach. Injectable antibiotics such as penicillin, ampicillin, or gentamicin, as well as intravenous trimethoprim/sulfamethoxazole, are essential for combating the bacterium. However, prevention remains the most effective defense. Individuals at heightened risk should steer clear of foods prone to harboring Listeria or ensure thorough cooking until piping hot (at least 180 degrees Fahrenheit) before consumption.

In conclusion, understanding the multifaceted threat posed by Listeria monocytogenes is paramount to safeguarding public health. By recognizing its resilience, insidious onset, and the necessity for preemptive measures, we can mitigate its devastating impact and protect vulnerable populations from its pernicious effects.
Understanding the Threat of Listeria monocytogenes

Foodborne botulism: Toxin and symptoms

Botulism is an uncommon yet severe disease characterized by the targeting of nerves by a toxin, resulting in breathing difficulties, muscle paralysis, and potentially fatal consequences. The toxin is produced by bacteria called Clostridium botulinum, and occasionally by Clostridium butyricum and Clostridium baratii.

Botulism can occur when food or wounds become contaminated. Additionally, it can arise when bacterial spores grow in the intestines of infants. In rare cases, botulism can also be caused by medical treatments or acts of bioterrorism.

In situations where foodborne botulism occurs, the harmful bacteria thrive and produce the toxin in oxygen-depleted environments. Consuming food contaminated with the botulinum toxin can result in foodborne botulism. Improperly canned, preserved, or fermented homemade foods are common sources of this type of botulism. While it is infrequent, store-bought foods can also become tainted with the toxin.

The World Health Organization (WHO) has identified botulinum toxin in various food items, including low-acid preserved vegetables like green beans, spinach, mushrooms, and beets; fish, including canned tuna, fermented, salted, and smoked fish; as well as meat products such as ham and sausage.

Symptoms of foodborne botulism usually appear within 12 to 36 hours after the toxin enters the human body. Botulism causes paralysis by affecting the nerves responsible for muscle stimulation and parts of the central nervous system. Initially, it impacts the nerves in the skull, leading to symptoms such as blurred vision, difficulty swallowing, double vision, stammering or stuttering, vocal disturbances, drooping eyelids, facial weakness, and weakness of the tongue. Subsequently, weakness progresses to the neck and arms, eventually affecting the respiratory and lower body muscles.
Foodborne botulism: Toxin and symptoms

Clostridium perfringens type A food poisoning

Clostridium perfringens food poisoning is usually a mild clostridial infection. Clostridium perfringens is widely distributed in feces, soil, air, and water.

Clostridium perfringens mostly can be found on raw meat and poultry, and in the intestines of animals. Contaminated meat has caused many outbreaks. Because the spores of some strains are resistant to temperatures as high as 100°C for more than l h, their presence in foods may be unavoidable.

Once inside the gastrointestinal tract, Clostridium perfringens produces an enterotoxin that acts on the small bowel. Clostridium perfringens types A, C, and D produce an enterotoxin that is implicated in the pathogenesis of disease caused by this organism.

Only Clostridium perfringens type A has been definitively linked to this food poisoning syndrome. Clostridium perfringens type A is a significant cause of foodborne illness in Western countries because of its spore-forming ability, rapid growth, and ability to produce an enterotoxin.

Clostridium perfringens type A strains producing alpha-toxin encoded by the cpa gene, also known as phospholipase C, encoded by the plc gene, that concomitantly produce the Clostridium perfringens enterotoxin (CPE).

Production and release of CPE in the gastrointestinal tract causes diarrhea and has been associated with spore formation and lysis of the mother cell in the gut.

Illness typically occurs 8-15 h after ingestion of the contaminated food. The symptoms, which include intense abdominal cramps, gas, and diarrhea (nausea and vomiting are rare), have been attributed to a protein enterotoxin produced during sporulation of the organism in the intestine.
Clostridium perfringens type A food poisoning

Brucellosis

Brucellosis is an infectious disease caused by Brucella species. There are several different strains of Brucella bacteria. Some types are seen in cows. Others occur in dogs, pigs, sheep, goats, and camels.

Humans generally acquire the disease through direct contact with infected animals, by eating or drinking contaminated animal products or by inhaling airborne agents. Most cases are caused by ingesting unpasteurized milk or cheese from infected goats or sheep.

The disease was described by George Cleghorn, a British army surgeon stationed on Minorca, in his 1751 work Observations on the Epidemical Diseases in Minorca from the Year 1744 to 1749.

People with brucellosis may develop fever, sweats, headaches, back pains, and physical weakness. In severe cases, the central nervous system and the lining of the heart may be affected.
Brucellosis

Rotavirus illness

Rotavirus is a very contagious virus that causes diarrhea. Before rotavirus vaccine was introduced in 2006, rotavirus was the leading cause of severe diarrhea in U.S. young children. Illnesses like rotavirus can actually be passed from an infected food handler to the product, putting the consumer at significant risk.

People can get infected with rotavirus if they get rotavirus particles in their mouth. The virus is spread from person to person, especially if people with diarrhea do not thoroughly wash their hands after a bowel movement. Infection also can occur if people touch their mouth after touching an object (such as a diaper or toy) contaminated by infected stool.

Rotavirus causes inflammation in the stomach and intestines. Symptoms usually start about two days after a person is exposed to rotavirus. The most common symptoms of rotavirus are severe watery diarrhea, vomiting, fever, and/or abdominal pain. Vomiting and watery diarrhea can last three to eight days.

Rotavirus spreads easily among infants and young children. They can spread rotavirus to family members and other people with whom they have close contact. Children are most likely to get rotavirus in the winter and spring (January through June).

Good hygiene, such as washing hands regularly, is important. But vaccination is the best way to prevent rotavirus infection.
Rotavirus illness

Cholera: Causes and symptoms

Cholera is an acute, diarrheal illness caused by the bacterium Vibrio cholerae. Of the more than 200 recognized V, cholerae serogroups, only cholera toxin-producing O1 and O139 serogroups have caused large epidemics and are defined as causing cholera.

A person may get cholera by drinking water or eating food that is contaminated with the cholera bacterium.

The source of the contamination is usually the feces of an infected person, or water contaminated with sewage. Cholera primarily occurs in settings where there is inadequate access to clean water and sanitation.

Cholera is characterized by copious watery diarrhea, without abdominal cramps or fever. Most individuals infected with toxigenic V. cholerae O1 have no symptoms, and some have only mild to moderate diarrhea lasting 3 to 7 days.

People exposed to cholera may experience mild profuse vomiting and dehydration. Cholera diarrhea can look like cloudy rice water.

Cholera can cause death from dehydration (the loss of water and salts from the body) within hours if not treated.
Cholera: Causes and symptoms

Hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is defined by the simultaneous occurrence of nonimmune hemolytic anemia, thrombocytopenia and acute renal failure.

Hemolytic uremic syndrome was described in 1955 by Gasser and colleagues. The overall incidence is estimated to be 2.1 cases per 100,000 persons/year with a peak incidence between 6 months and 4 years of age.

The signs and symptoms of Hemolytic uremic syndrome may vary, depending on the cause. Most cases of Hemolytic uremic syndrome are caused by infection with certain strains of E. coli bacteria, which first affect the digestive tract.

The illness usually caused by infection with Shiga toxin-producing Escherichia coli O157 (STEC O157).

The initial signs and symptoms of this form of Hemolytic uremic syndrome may include:
*Diarrhea, which is often bloody
*Abdominal pain, cramping or bloating
*Vomiting
*Fever

The characteristic lesion, thrombotic microangiopathy, is unique to this syndrome and consists of vessel wall thickening (capillaries and arterioles), with swelling and detachment of the endothelial cells from the basement membrane and accumulation of fluffy material in the subendothelium.
Hemolytic uremic syndrome

Cryptosporidiosis: Infection and transmission

Cryptosporidiosis is a disease caused by Cryptosporidium spp, an obligate intracellular protozoan parasite. Cryptosporidium muris was first described by Tyzzer in 1910 and Cryptosporidium parvum was described two years later. However, it was not until the 1970s that Cryptosporidium was determined to be a significant cause of gastrointestinal disease in humans.

It is a frequent cause of diarrheal disease in humans, and several groups of humans are particularly susceptible to cryptosporidiosis. In developing countries, Cryptosporidium infections occur mostly in children younger than 5 years.

In immunocompromised persons such as human immunodeficiency virus-positive (HIV) patients, the incidence and severity of cryptosporidiosis increases as the CD4 lymphocyte cell count falls.

The persistent diarrhea and malabsorption can become life-threatening, particularly in acquired immunodeficiency syndrome (AIDS) patients.

Cryptosporidium is a small protozoan parasite that infects the microvillous region of epithelial cells in the digestive and respiratory tract of vertebrates. It is an obligate intracellular parasite of man and other mammals, birds, reptiles and fish. It requires its host to multiply.

When the oocysts enter the gastrointestinal tract, the invasive Cryptosporidium causes damage to the small intestinal epithelium. It disrupts the barrier function and absorption capability that leads to mild-to-severe diarrhea and other abdominal symptoms.

Cryptosporidiosis is an opportunistic parasitosis. It is characterized by self-limiting gastroenteritis in otherwise healthy people, while it is more severe in immunocompromised subjects in HIV-infected patients and constitutes a serious threat leading to chronic or fulminant disease, wasting and death.

The infection is spread in a number of ways: from person to person, from animals, via food, and by water. Cryptosporidiosis is now the most common cause of waterborne disease in the world.

Cryptosporidium oocysts transmission can occur following direct or indirect contact with an infected host usually via the fecal–oral route. Person to-person contact, zoonosis, and the consumption of contaminated food or water are well known mechanisms for fecal–oral transmission.

The largest cryptosporidiosis outbreak reported to date in the USA occurred in Milwaukee, Wisconsin in 1993 when over 403,000 individuals were sickened out of a potentially exposed population of 1.6 million.
Cryptosporidiosis: Infection and transmission 

Norovirus infection

Norovirus (NoV)) is a highly contagious virus. Norovirus infection causes gastroenteritis (inflammation of the stomach and intestines). Human NoV, previously known as Norwalk virus, was first identified in stool specimens collected during an outbreak of gastroenteritis in Norwalk, OH. It was initially described in 1929 as “winter vomiting disease”.

NoVs are the major cause of acute nonbacterial human gastroenteritis, being transmitted from food or from person to person via a fecal-oral route, affecting population all over the world.

Indirect evidence in epidemiological studies shows that the virus transmission can be airborne, such as in explosive vomiting occurred during the disease. Transmission can also happen via water reservoir when groundwater is contaminated.

NoVs infect persons of all ages. Although NoV disease outbreaks are reported year-round, they peak during months with cold weather in temperate climates. Norovirus can spread quickly in enclosed places like daycare centers, nursing homes, schools, and cruise ships.

Clinical NoV infection generally has an incubation of 24–48 h and is characterized by acute onset of nausea, vomiting, abdominal cramps, myalgias, and non-bloody diarrhea.

NoV illness can present with relatively severe symptoms of vomiting and non-bloody diarrhea, with symptoms usually resolving in 2–3 days.

It only takes a very small amount of norovirus particles (fewer than 100) to make the person sick. People with norovirus illness shed billions of virus particles in their stool and vomit and can easily infect others.
Norovirus infection

Paratyphoid Fever caused by Salmonella enterica serovars Paratyphi

Enteric fever (typhoid and paratyphoid fever) is caused by Salmonella enterica serovars Typhi (S. Typhi) and Salmonella enterica serovars Paratyphi (S. Paratyphi). S. Paratyphi A and B (and, uncommonly, S. Paratyphi C) cause a disease that is clinically indistinguishable from typhoid fever, particularly in parts of Asia.

Generally, S. Paratyphi A is a Gram-negative bacterium that belongs to the Enterobacteriaceae family. Paratyphoid Fever is the same as for typhoid fever but disease is usually milder. S. Paratyphi A can be isolated from the blood and faeces from paratyphoid fever patients. This bacterium causes a milder infection with lower mortality and chronic carriage rate compared to S.Typhi.

Paratyphoid fever is transmitted by ingestion of food or water contaminated with feces or urine of infected people or directly from person to person. Shellfish harvested from sewage-contaminated water are potential vehicles, as are fruits and vegetables grown in soil fertilized with human waste. Family contact could be a factor of transmission as well, but a recent report on the risk factors for the disease showed that paratyphoid infections occur mostly outside the household.

The symptoms of typhoid and paratyphoid fever are similar although paratyphoid tends to be less severe than typhoid. Symptoms of S. Paratyphi A infection include fever, headache, diarrhoea or constipation, malaise, anorexia, nausea, dry cough, gastrointestinal symp-toms, abdominal pain, chills, raised spots or rashes on body.

Typhoid can be prevented by being vaccinated before travelling to a developing country. Additionally, people travelling in developing countries should:
*avoid uncooked foods, including fruit unless it is able to be peeled
*avoid untreated water, including ice
*drink from sealed containers (i.e. bottles or cans)
*wash their hands after going to the toilet and before eating
*avoid eating from street stalls
*ensure hot food is thoroughly cooked and eaten while hot.
Paratyphoid Fever caused by Salmonella enterica serovars Paratyphi

Symptoms of E. coli O157:H7 infection

E. coli O157:H7 was given to a deadly strain of chemical compounds found on the bacterium’s surface. Sources of human infection have included, among others, poorly cooked meat (especially hamburger), apple juice, water (including water parks), vegetables and fruit from salad bars, and milk products such as yogurt and unpasteurized milk.

Infection often causes severe bloody diarrhea and abdominal cramps; sometimes the infection causes non-bloody diarrhea. Frequently, no fever is present. It should be noted that these symptoms are common to a variety of diseases, and may be caused by sources other than contaminated drinking water.

Patients initially complain of symptoms similar to viral gastroenteritis abdominal cramping with significant abdominal pain and tenderness; flatulence; elevated temperatures; and voluminous, water diarrhea.

The diarrhea eventually becomes bloody; 91% of patients report bloody stools at some time during the course of the disease. Symptoms of infection with E. coli O157:H7 usually resolve within 8 days. Those whose primary symptom is diarrhea usually recover completely. Those with more serious infections may suffer kidney impairment or failure and the complications associate with it.
Symptoms of E. coli O157:H7 infection

What are the symptoms of cryptosporidiosis?

Long term sequelae resulting from infection can be common and van cause non-intestinal symptoms. The first signs and symptoms of cryptosporidium infection usually appear within a week after infection and may include:
*Watery diarrhea
*Dehydration
*Lack of appetite
*Weight loss
*Abdominal pain
*Mild Fever
*Nausea
*Anorexia
*Vomiting
*Respiratory problems

As might be expected, many individuals experienced multiple symptoms. In people with a profound immunodeficiency, there can be symptoms that are different and more prolonged, and disease can result in an earlier death than would be the case of the patient had not been infected.

Symptomatic diarrhea may be marked by stool volumes that exceed 6 liters per day. Intestinal infections may extend from the small intestine into then colon, stomach, and esophagus and may involved a variety of extra-intestinal organs and tissues.
What are the symptoms of cryptosporidiosis?