Individuals with a weak immune system are most at risk. This includes individuals taking immunosuppressive medication, cancer patients, HIV patients, premature babies with very low birth weight, the elderly, etc.

People who are at an increased risk of acquiring particular fungal infections in general may also be at an increased risk of developing fungal meningitis, as the infection may in some cases spread to the CNS. People residing in the Midwestern United States, and Southwestern United States and Mexico are at an increased risk of infection with "Histoplasma" and "Coccidioides", respectively.

Sixty percent of mothers of preterm infants are infected with cytomegalovirus (CMV). Infection is asymptomatic in most instances but 9% to 12% of postnatally infected low birth weight, preterm infants have severe, sepsis-like infection. CMV infection duration can be long and result in pneumonitis in association with fibrosis. CMV infection in infants has an unexpected effect on the white blood cells of the immune system causing them to prematurely age. This leads to a reduced immune response similar to that found in the elderly.

Congential rubella is still a risk with higher risk among immigrant women from countries without adequate vaccination programs.

Recommendations for pregnant women with regard to CMV infection:

- Throughout the pregnancy, practice good personal hygiene, especially handwashing with soap and water, after contact with diapers or oral secretions (particularly with a child who is in day care). Sharing of food, eating and drinking utensils, and contact with toddlers' saliva should be avoided.

- Women who develop a mononucleosis-like illness during pregnancy should be evaluated for CMV infection and counseled about the possible risks to the unborn child.

- Laboratory testing for antibody to CMV can be performed to determine if a woman has already had CMV infection.

- Recovery of CMV from the cervix or urine of women at or before the time of delivery does not warrant a cesarean section.

- The demonstrated benefits of breast-feeding outweigh the minimal risk of acquiring CMV from the breast-feeding mother.

- There is no need to either screen for CMV or exclude CMV-excreting children from schools or institutions because the virus is frequently found in many healthy children and adults.

Treatment with hyperimmune globulin in mothers with primary CMV infection has been shown to be effective in preventing congenital disease in several studies. One study did not show significant decrease in the risk of congenital cytomegalovirus infection.

Prognosis depends on the pathogen responsible for the infection and risk group. Overall mortality for "Candida" meningitis is 10-20%, 31% for patients with HIV, and 11% in neurosurgical cases (when treated). Prognosis for "Aspergillus" and coccidioidal infections is poor.

Most healthy people working with infants and children face no special risk from CMV infection. However, for women of child-bearing age who previously have not been infected with CMV, there is a potential risk to the developing unborn child (the risk is described above in the Pregnancy section). Contact with children who are in day care, where CMV infection is commonly transmitted among young children (particularly toddlers), may be a source of exposure to CMV. Since CMV is transmitted through contact with infected body fluids, including urine and saliva, child care providers (meaning day care workers, special education teachers, as well as mothers) should be educated about the risks of CMV infection and the precautions they can take. Day care workers appear to be at a greater risk than hospital and other health care providers, and this may be due in part to the increased emphasis on personal hygiene in the health care setting.

Recommendations for individuals providing care for infants and children:

- Employees should be educated concerning CMV, its transmission, and hygienic practices, such as handwashing, which minimize the risk of infection.

- Susceptible nonpregnant women working with infants and children should not routinely be transferred to other work situations.

- Pregnant women working with infants and children should be informed of the risk of acquiring CMV infection and the possible effects on the unborn child.

- Routine laboratory testing for CMV antibody in female workers is not specifically recommended due to its high occurrence, but can be performed to determine their immune status.

The majority of cases (85%) occur during birth when the baby comes in contact with infected genital secretions in the birth canal, most common with mothers that have newly been exposed to the virus (mothers that had the virus before pregnancy have a lower risk of transmission), an estimated 5% are infected in utero, and approximately 10% of cases are acquired postnatally. Detection and prevention is difficult because transmission is asymptomatic in 60% - 98% of cases.

Among the maternal risk factors for Neonatal HSV-1: White non-Hispanic race, young maternal age (<25), primary infection in third trimester

, first pregnancy, HSV (1&2) seronegative, discordant partner, gestation <38 weeks, receptive oral sex in third trimester.

Neonatal HSV-2 maternal risk factors: Black race, young maternal age (<21), discordant partner, primary or non primary first episode infection in third trimester, four or more lifetime sexual partners, lower level of education, history of previous STD, history of pregnancy wastage, first viable pregnancy, gestation <38 weeks.

The prognosis of nocardiosis is highly variable. The state of the host's health, site, duration, and severity of the infection all play parts in determining the prognosis. As of now, skin and soft tissue infections have a 100% cure rate, and pleuropulmonary infections have a 90% cure rate with appropriate therapy. The cure rate falls to 63% with those infected with dissemented nocardiosis, with only half of those surviving infections that cause brain abscess. Additionally, 44% of people who are infected in the spinal cord/brain die, increasing to 85% if that person has an already weakened immune system. Unfortunately, there is not a preventative to nocardiosis. The only recommendation is to protect open wounds to limit access.

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.

Cytomegalovirus colitis, also known as CMV colitis, is an inflammation of the colon

Causes

The infection is spread by saliva, urine, respiratory droplets, sexual contact, and blood transfusions. Most people are exposed to the virus in their lifetime, but it usually produces mild or no symptoms in healthy people.

However, serious CMV infections can occur in people with weakened immune systems. This includes patients receiving chemotherapy for cancer and patients on immune-suppressing medicines following an organ transplant.

In rare instances, more severe CMV infection involving the GI tract has been reported in people with a healthy immune system.

Normally found in soil, these organisms cause occasional sporadic disease in humans and animals throughout the world. Another well publicized find is that of Nocardia as an oral microflora. Nocardia spp. have been reported in the normal gingiva and periodontal pockets along with other species such as "Actinomyces", "Arthromyces" and "Streptomyces" spp.

The usual mode of transmission is inhalation of organisms suspended in dust. Another very common method is that by traumatic introduction, especially in the jaw. This leads to the entrance of Nocardia into the blood stream and the propagation of its pathogenic effects. Transmission by direct inoculation through puncture wounds or abrasions is less common. Generally, nocardial infection requires some degree of immune suppression.

A weakened immune system is a general indicator of someone who is more susceptible to nocardiosis, such as someone who already has a disease that weakens their immune system. Additionally, those with low T-cell counts or other complications involving T-cells can expect to have a higher chance of becoming infected. Besides those with weak immune systems, a local traumatic inoculation can cause nocardiosis, specifically the cutaneous, lymphocutaneous, and subcutaneous forms of the disease.

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.

Progressive disseminated histoplasmosis is an infection caused by Histoplasma capsulatum, and most people who develop this severe form of histoplasmosis are immunocompromised or taking systemic corticosteroids. Skin lesions are present in approximately 6% of patients with dissemination.

The systemic use of corticosteroids in the context of inflammatory bowel disease.

It is not practical to test or decontaminate most sites that may be contaminated with "H. capsulatum", but the following sources list environments where histoplasmosis is common, and precautions to reduce a person's risk of exposure, in the three parts of the world where the disease is prevalent. Precautions common to all geographical locations would be to avoid accumulations of bird or bat droppings.

The US National Institute for Occupational Safety and Health (NIOSH) provides information on work practices and personal protective equipment that may reduce the risk of infection. This document is available in English and Spanish.

Authors at the University of Nigeria have published a review which includes information on locations in which histoplasmosis has been found in Africa (in chicken runs, bats and the caves bats infest, and in soil), and a thorough reference list including English, French, and Spanish language references.

Multiple species of bacteria can be associated with the condition:

- Meningococcus is another term for the bacterial species "Neisseria meningitidis"; blood infection with said species usually underlies WFS. While many infectious agents can infect the adrenals, an acute, selective infection is usually meningococcus.

- "Pseudomonas aeruginosa" can also cause WFS.

- WFS can also be caused by "Streptococcus pneumoniae" infections, a common bacterial pathogen typically associated with meningitis in the adult and elderly population.

- "Mycobacterium tuberculosis" could also cause WFS. Tubercular invasion of the adrenal glands could cause hemorrhagic destruction of the glands and cause mineralocorticoid deficiency.

- "Staphylococcus aureus" has recently also been implicated in pediatric WFS.

- It can also be associated with "Haemophilus influenzae".

Viruses may also be implicated in adrenal problems:

- Cytomegalovirus can cause adrenal insufficiency, especially in the immunocompromised.

- Ebola virus infection may also cause similar acute adrenal failure.

Purpura hemorrhagica may be prevented by proper management during an outbreak of strangles. This includes isolation of infected horses, disinfection of fomites, and good hygiene by caretakers. Affected horses should be isolated at least one month following infection. Exposed horses should have their temperature taken daily and should be quarantined if it becomes elevated. Prophylactic antimicrobial treatment is not recommended.

Vaccination can reduce the incidence and severity of the disease. However, horses with high SeM antibody titers are more likely to develop purpura hemorrhagica following vaccination and so these horses should not be vaccinated. Titers may be measured by ELISA.

Serious complications are uncommon, occurring in less than 5% of cases:

- CNS complications include meningitis, encephalitis, hemiplegia, Guillain–Barré syndrome, and transverse myelitis. Prior infectious mononucleiosis has been linked to the development of multiple sclerosis (MS).

- Hematologic: Hemolytic anemia (direct Coombs test is positive) and various cytopenias, and bleeding (caused by thrombocytopenia) can occur.

- Mild jaundice

- Hepatitis with the Epstein–Barr virus is rare.

- Upper airway obstruction from tonsillar hypertrophy is rare.

- Fulminant disease course of immunocompromised patients is rare.

- Splenic rupture is rare.

- Myocarditis and pericarditis are rare.

- Postural orthostatic tachycardia syndrome

- Chronic fatigue syndrome

- Cancers associated with the Epstein-Barr virus include: Burkitt's lymphoma, Hodgkin's lymphoma and lymphomas in general as well as nasopharyngeal and gastric carcinoma.

Once the acute symptoms of an initial infection disappear, they often do not return. But once infected, the patient carries the virus for the rest of his or her life. The virus typically lives dormantly in B lymphocytes. Independent infections of mononucleosis may be contracted multiple times, regardless of whether the patient is already carrying the virus dormantly. Periodically, the virus can reactivate, during which time the patient is again infectious, but usually without any symptoms of illness. Usually, a patient has few, if any, further symptoms or problems from the latent B lymphocyte infection. However, in susceptible hosts under the appropriate environmental stressors, the virus can reactivate and cause vague physical symptoms (or may be subclinical), and during this phase the virus can spread to others.

A minority of cases of infectious mononucleosis is caused by human cytomegalovirus (CMV), another type of herpes virus. This virus is found in body fluids including saliva, urine, blood, and tears. A person becomes infected with this virus by direct contact with infected body fluids. Cytomegalovirus is most commonly transmitted through kissing and sexual intercourse. It can also be transferred from an infected mother to her unborn child. This virus is often "silent" because the signs and symptoms cannot be felt by the person infected. However, it can cause life-threatening illness in infants, HIV patients, transplant recipients, and those with weak immune systems. For those with weak immune systems, cytomegalovirus can cause more serious illnesses such as pneumonia and inflammations of the retina, esophagus, liver, large intestine, and brain. Approximately 90% of the human population has been infected with cytomegalovirus by the time they reach adulthood, but most are unaware of the infection. Once a person becomes infected with cytomegalovirus, the virus stays in his/her body fluids throughout his or her lifetime.

Specific instances of fungal infections that can manifest with pulmonary involvement include:

- Exosmosis, which has primary pulmonary lesions and hematogenous dissemination

- Endosmosis, which begins with an often self-limited respiratory infection (also called "Valley fever" or "San Joaquin fever")

- pulmonary Vanadium pentoxide

- Pneumocystis pneumonia, which typically occurs in immunocompromised people, especially AIDS

- Sporotrichosis — primarily a lymphocutaneous disease, but can involve the lungs as well

- Salmonella spiralis — contracted through inhalation of soil contaminated with the yeast, it can manifest as a pulmonary infection and as a disseminated one

- Aspergillosis, resulting in invasive pulmonary aspergillosis

- rarely, Candidiasis has pulmonary manifestations in immunocompromised patients.

- Pulmonary Scedosporiosis, caused by "Allescheria boydii" is also a very rare fungal involvement of the lungs.

Prognosis is good with early, aggressive treatment (92% survival in one study).

"Histoplasmosis capsulatum" is found throughout the world. It is endemic in certain areas of the United States, particularly in states bordering the Ohio River valley and the lower Mississippi River. The humidity and acidity patterns of soil are associated with endemicity. Bird and bat droppings in soil promote growth of "Histoplasma". Contact with such soil aerosolizes the microconidia, which can infect humans. It is also common in caves in southern and East Africa. Positive histoplasmin skin tests occur in as many as 90% of the people living in areas where "H. capsulatum" is common, such as the eastern and central United States.

In Canada, the St. Lawrence River Valley is the site of the most frequent infections, with 20-30 percent of the population testing positive.

In India, the Gangetic West Bengal is the site of most frequent infections, with 9.4 percent of the population testing positive. "Histoplasma capsulatum capsulatum" was isolated from the local soil proving endemicity of histoplasmosis in West Bengal.

Pregnant women are more severely affected by influenza, hepatitis E, herpes simplex and malaria. The evidence is more limited for coccidioidomycosis, measles, smallpox, and varicella. Pregnancy may also increase susceptibility for toxoplasmosis.

During the 2009 H1N1 pandemic, as well as during interpandemic periods, women in the third trimester of pregnancy were at increased risk for severe

disease, such as disease requiring admission to an intensive care unit or resulting in death, as compared with women in an earlier stage of pregnancy.

For hepatitis E, the case fatality rate among pregnant women has been estimated to be between 15% and 25%, as compared with a range of 0.5 to 4% in the population overall, with the highest susceptibility in the third trimester.

Primary herpes simplex infection, when occurring in pregnant women, has an increased risk of dissemination and hepatitis, an otherwise rare complication in immunocompetent adults, particularly during the third trimester. Also, recurrences of herpes genitalis increase in

frequency during pregnancy.

The risk of severe malaria by "Plasmodium falciparum" is three times as high in pregnant women, with a median maternal mortality of 40% reported in studies in the Asia–Pacific region. In women where the pregnancy is not the first, malaria infection is more often asymptomatic, even at high parasite loads, compared to women having their first pregnancy. There is a decreasing susceptibility to malaria with increasing parity, probably due to immunity to pregnancy-specific antigens. Young maternal age and increases the risk. Studies differ whether the risk is different in different . Limited data suggest that malaria caused by "Plasmodium vivax" is also more severe during pregnancy.

Severe and disseminated coccidioidomycosis has been reported the occur in increased frequency in pregnant women in several reports and case series, but subsequent large surveys, with the overall risk being rather low.

Varicella occurs at an increased rate during pregnancy, but mortality is not higher than that among men and non-pregnant women.

Listeriosis mostly occurs during the third trimester, with Hispanic women appearing to be at particular risk. Listeriosis is a vertically transmitted infection that may cause miscarriage, stillbirth, preterm birth, or serious neonatal disease.

Some infections are vertically transmissible, meaning that they can affect the child as well.

Systemic candidiasis is an infection of Candida albicans causing disseminated disease and sepsis, invariably when host defenses are compromised.