Herpes simplex virus is commonly found in humans, yet uncommonly results in systemic manifestations. Suppression of HIV with antiretroviral medications, careful monitoring of immunosuppressive medications are important means of prevention. Antiviral prophylaxis such as daily acyclovir in immunocompromised individuals may be considered.

Reflux esophagitis

A backflow of stomach acids into the esophagus that causes irritation, chronic inflammation, and tissue damage in the esophagus.

Infectious esophagitis

Esophagitis that happens due to a viral, fungal, parasitic or bacterial infection. More likely to happen to people who have an immunodeficiency. Types include:

Fungal

- Candida (Esophageal candidiasis)

Viral

- Herpes simplex (Herpes esophagitis)

- Cytomegalovirus

Drug-induced esophagitis

Damage to the esophagus due to medications. If the esophagus is not coated or if the medicine is not taken with enough liquid, it can damage the tissues.

Eosinophilic esophagitis

This esophagitis is caused by a high concentration of eosinophils in the esophagus. The presence of eosinophils in the esophagus may be due to an allergen or acid reflux. This esophagitis can be triggered by allergies to food or to inhaled allergens. This type is still poorly understood.

Lymphocytic esophagitis

Lymphocytic esophagitis is when there is an increased amount of lymphocytes in the lining of the esophagus. It is a rare condition. It could be connected to eosinophilic esophagitis.

Causes

Esophagitis cannot be spread. However, infections can be spread by those who have infectious esophagitis. Esophagitis can develop due to many causes. GERD is the most common cause of esophagitis because of the backflow of acid from the stomach, which can irritate the lining of the esophagus.

Other causes include:

- Medicines- Can cause esophageal damage that can lead to esophageal ulcers

- Nonsteroidal anti-inflammatory drugs (NSAIDS)-aspirin, naproxen sodium, and ibuprofen. Known to irritate the GI tract.

- Antibiotics- doxycycline and tetracycline

- Quinidine

- Biphosphonates- used to treat osteoporosis

- Steroids

- Potassium chloride

- Chemical injury by alkaline or acid solutions

- Physical injury resulting from nasogastric tubes.

- Alcohol abuse- Can wear down the lining of the esophagus.

- Crohn's disease – a type of IBD and an autoimmune disease that can cause esophagitis if it attacks the esophagus.

- Stress- Can cause higher levels of acid reflux

- Radiation therapy-Can affect the immune system.

- Allergies (food, inhalants)- Allergies can stimulate eosinophilic esophagitis.

- Infection-People with an immunodeficiencies have a higher chance of developing esophagitis.

- Vitamins and supplements (iron, Vitamin C, and potassium)-Supplements and minerals can be hard on the GI tract.

- Vomiting- Acid can irritate esophagus.

- Hernias-A hernia can poke through the diaphragm muscle and can inhibit the stomach acid and food from draining quickly.

- Surgery

Prevention

Since there can be many causes underlying esophagitis, it is important to try to find the cause to help to prevent esophagitis. To prevent reflux esophagitis, avoid acidic foods, caffeine, eating before going to bed, alcohol, fatty meals, and smoking. To prevent drug-induced esophagitis, drink plenty of liquids when taking medicines, take an alternative drug, and do not take medicines while lying down, before sleeping, or too many at one time. Esophagitis is more prevalent in adults and does not discriminate.

Antivirals such as acyclovir, famciclovir, or valacyclovir may be used. Intravenous acyclovir is reserved for individuals who cannot swallow due to the pain, individuals with other systemic manifestations of herpes or severely immunocompromised individuals.

Most household disinfectants will inactivate FHV-1. The virus can survive up to 18 hours in a damp environment, but less in a dry environment and only shortly as an aerosol.

There is a vaccine for FHV-1 available (ATCvet code: , plus various combination vaccines), but although it limits or weakens the severity of the disease and may reduce viral shedding, it does not prevent infection with FVR. Studies have shown a duration of immunity of this vaccine to be at least three years. The use of serology to demonstrate circulating antibodies to FHV-1 has been shown to have a positive predictive value for indicating protection from this disease.

Cytomegalovirus esophagitis is a form of esophagitis associated with cytomegalovirus.

It is likely to present with a single, deep ulcer as opposed to the multiple shallow ulcers seen in herpes esophagitis.

Numerous factors have been suggested and linked to a higher risk of acquiring the infection, inclusive of malnutrition, vitamin A deficiency, absence of breastfeeding during the early stages of life, environmental pollution and overcrowding.

Mortality caused by HPIVs in developed regions of the world remains rare. Where mortality has occurred, it is principally in the three core risk groups (very young, elderly and immuno-compromised). Long term changes can however be associated with airway remodelling and are believed to be a significant cause of morbidity. The exact associations between HPIVs and diseases such as chronic obstructive pulmonary disease (COPD) are still being investigated.

In developing regions of the world, the highest risk group in terms of mortality remains pre-school children. Mortality may be as a consequence of primary viral infection or secondary problems such as bacterial infection. Predispositions, such as malnutrition and other deficiencies may further elevate the chances of mortality associated with infection.

Overall, LRI's cause approximately 25–30% of total deaths in pre-school children in the developing world. HPIVs is believed to be associated with 10% of all LRI cases, thus remaining a significant cause of mortality.

The current first-line treatment is fluconazole, 200 mg. on the first day, followed by daily dosing of 100 mg. for at least 21 days total. Treatment should continue for 14 days after relief of symptoms.

Other therapy options include:

- nystatin is not an effective treatment for esophageal candidiasis. It can be used as (swish, do not swallow) treatment for oral candidiasis that occurs with the use of asthma pumps.

- other oral triazoles, such as itraconazole

- caspofungin, used in refractory or systemic cases

- amphotericin, used in refractory or systemic cases

A recent study from The Cleveland Clinic reported that BK viremia load > 185 000 copies/ml at the time of first positive BKV diagnosis - to be the strongest predictor for BKVAN (97% specificity and 75% sensitivity). In addition the BKV peak viral loads in blood reaching 223 000 copies/ml at any time was found to be predictive for BKVAN (91% specificity and 88% sensitivity) .

Esophageal candidiasis is an opportunistic infection of the esophagus by "Candida albicans". The disease usually occurs in patients in immunocompromised states, including post-chemotherapy and in AIDS. However, it can also occur in patients with no predisposing risk factors, and is more likely to be asymptomatic in those patients. It is also known as candidal esophagitis or monilial esophagitis.

It is not known how this virus is transmitted. It is known, however, that the virus is spread from person to person, and not from an animal source. It has been suggested that this virus may be transmitted through respiratory fluids or urine, since infected individuals periodically excrete virus in the urine. A survey of 400 healthy blood donors was reported as showing that 82% were positive for IgG against BK virus.

Among individuals being treated in intensive care units, the mortality rate is about 30-50% when systemic candidiasis develops.

Adenoiditis occurs mainly in childhood, often associated with acute tonsillitis. Incidence decreases with age, with adenoiditis being rare in children over 15 years due to physiological atrophy of the adenoid tissue.

The best prevention against viral pneumonia is vaccination against influenza, adenovirus, chickenpox, herpes zoster, measles, and rubella.

A diet that supports the immune system and is not high in simple carbohydrates contributes to a healthy balance of the oral and intestinal flora. While yeast infections are associated with diabetes, the level of blood sugar control may not affect the risk. Wearing cotton underwear may help to reduce the risk of developing skin and vaginal yeast infections, along with not wearing wet clothes for long periods of time.

Oral hygiene can help prevent oral candidiasis when people have a weakened immune system. For people undergoing cancer treatment, chlorhexidine mouthwash can prevent or reduce thrush. People who use inhaled corticosteroids can reduce the risk of developing oral candidiasis by rinsing the mouth with water or mouthwash after using the inhaler.

For women who experience recurrent yeast infections, there is limited evidence that oral or intravaginal probiotics help to prevent future infections. This includes either as pills or as yogurt.

It is currently believed that bacterial biofilms play an integral role in the harboring of chronic infection by tonsil and adenoid tissue so contributing to recurrent sinusitis and recurrent or persistent ear disease. Also, enlarged adenoids and tonsils may lead to the obstruction of the breathing patterns in children, causing apnea during sleep.

The most common bacteria isolated are Haemophilus influenzae, group A beta-hemolytic Streptococcus, Staphylococcus aureus, Moraxella catarrhalis, and Streptococcus pneumoniea. Heamophilus influenza, Moraxella catarrhalis and Streptococcus pneumonia are the three most resistant pathogens of otitis and rhinosinisitis in children suffering from these diseases.

Many viral infections of the central nervous system occur in seasonal peaks or as epidemics, whereas others, such as herpes simplex encephalitis, are sporadic. In endemic areas it is mostly a disease of children, but as the disease spreads to new regions, or nonimmune travelers visit endemic regions, nonimmune adults are also affected.

Post-viral cough can be resistant to treatment. Post-viral cough usually goes away on its own; however, cough suppressants containing codeine may be prescribed. A study has claimed theobromine in dark chocolate is more effective.

One possible cause for post-viral cough is that the receptors that are responsible for stimulating the cough during the respiratory tract infection are up-regulated by respiratory tract infection and continue to stimulate even after the virus has disappeared.

Meningitis is a very common in children. Newborns can develop herpes virus infections through contact with infected secretions in the birth canal. Other viral infections are acquired by breathing air contaminated with virus-containing droplets exhaled by an infected person. Arbovirus infections are acquired from bites by infected insects (called epidemic encephalitis). Viral central nervous system infections in newborns and infants usually begin with fever. The inability of infants to communicate directly makes it difficult to understand their symptoms. Newborns may have no other symptoms and may initially not otherwise appear ill. Infants older than a month or so typically become irritable and fussy and refuse to eat. Vomiting is common. Sometimes the soft spot on top of a newborn's head (fontanelle) bulges, indicating an increase in pressure on the brain. Because irritation of the meninges is worsened by movement, an infant with meningitis may cry more, rather than calm down, when picked up and rocked. Some infants develop a strange, high-pitched cry. Infants with encephalitis often have seizures or other abnormal movements. Infants with severe encephalitis may become lethargic and comatose and then die. To make the diagnosis of meningitis or the diagnosis of encephalitis, doctors do a spinal tap (lumbar puncture) to obtain cerebrospinal fluid (CSF) for laboratory analysis in children.

GERD is caused by a failure of the lower esophageal sphincter. In healthy patients, the "Angle of His"—the angle at which the esophagus enters the stomach—creates a valve that prevents duodenal bile, enzymes, and stomach acid from traveling back into the esophagus where they can cause burning and inflammation of sensitive esophageal tissue.

Factors that can contribute to GERD:

- Hiatal hernia, which increases the likelihood of GERD due to mechanical and motility factors.

- Obesity: increasing body mass index is associated with more severe GERD. In a large series of 2,000 patients with symptomatic reflux disease, it has been shown that 13% of changes in esophageal acid exposure is attributable to changes in body mass index.

- Zollinger-Ellison syndrome, which can be present with increased gastric acidity due to gastrin production.

- A high blood calcium level, which can increase gastrin production, leading to increased acidity.

- Scleroderma and systemic sclerosis, which can feature esophageal dysmotility.

- The use of medicines such as prednisolone.

- Visceroptosis or Glénard syndrome, in which the stomach has sunk in the abdomen upsetting the motility and acid secretion of the stomach.

GERD has been linked to a variety of respiratory and laryngeal complaints such as laryngitis, chronic cough, pulmonary fibrosis, earache, and asthma, even when not clinically apparent. These atypical manifestations of GERD are commonly referred to as laryngopharyngeal reflux (LPR) or as extraesophageal reflux disease (EERD).

Factors that have been linked with GERD, but not conclusively:

- Obstructive sleep apnea

- Gallstones, which can impede the flow of bile into the duodenum, which can affect the ability to neutralize gastric acid

In 1999, a review of existing studies found that, on average, 40% of GERD patients also had "H. pylori" infection. The eradication of "H. pylori" can lead to an increase in acid secretion, leading to the question of whether "H. pylori"-infected GERD patients are any different than non-infected GERD patients. A double-blind study, reported in 2004, found no clinically significant difference between these two types of patients with regard to the subjective or objective measures of disease severity.

It can also be caused by certain medical conditions, such as:

- Ulcers

- Abscesses

- Upper respiratory tract infections

- Inflammation or infection of the mouth, tongue, or throat (esophagitis, pharyngitis, tonsillitis, epiglottitis)

- Immune disorders

- Oral or throat cancer

Gastroesophageal reflux disease (GERD) affects approximately 40% of adults. Strictures occur in 7 to 23% of patients with GERD who are untreated.