Many individuals develop a variety of infections but quickly overcome them. However, some individuals are unfortunate and develop chronic or persistent infections. In the majority of cases, persistent infections are caused by viruses and not bacteria. The common viruses that can cause chronic infection include measles, hepatitis, various viruses that affect the brain (mad cow) , herpes, infectious mononucleosis and Cytomegalovirus (CMV). Bacteria can also cause chronic infections in individuals with diabetes, those with compromised immunity and in individuals who smoke.

Diagnosis

The diagnosis of persistent infections can be difficult as there are no specific signs and symptoms. If an infection is suspected, blood, urine and sputum cultures are usually the first step. Chest x ray and stool analysis may provide a clue. Sometimes fluid from the spinal cord is obtained to ensure that there is no brain infection.

Symptoms

• Extreme fatigue which may be ongoing for more than 2-3 months
• Continued weight loss
• Low grade or spiking fever
• Night sweats and chills
• Vague body aches and pain

Primary and secondary

Primary and secondary infection may either refer to succeeding infections or different stages of one and the same infection such as in acute herpes labialis infection. In the latter case, acute infection may also be used, as in acute HIV infection.

Bacterial or viral

Bacterial and viral infections can both cause symptoms such as malaise, fever, and chills. It can be difficult to distinguish which is the cause of a specific infection. It's important to distinguish, because viral infections cannot be cured by antibiotics.

For infection to occur in a human, the chain of events must happen. Infections do not occur by chance but involve many factors. The chain of events involves several steps which include the infectious agent, reservoir, susceptible host, portal of entry, mode of transmission and portal of exit. Each of the links must be present in a chronological order for an infection to develop. Understanding these steps helps health care workers target the infection and prevent it from occurring in the first place. Each one of these links has an integral role in infection

Specific bacterial infections

H pylori is associated with inflammation of the stomach and is a common cause of stomach ulcers and gastritis. At least 10 percent of individuals infected with h pylori develop an ulcer. Moreover, there is an increased risk of stomach cancer after an infection with this organism.

Methicillin-resistant staphylococcus aureus predominantly affects the skin and is considered to be a super bug as it is very resistant to antibiotics. This bacteria is known to generate a variety of toxic enzymes which can lead to vomiting, diarrhea, shock and sepsis. MRSA is quite common in hospitals and today there is a great cause for concern about its spread.

Occult infection

An occult infection is medical terminology for a "hidden" infection, that is, one which presents no symptoms. Dr. Fran Giampietro discovered this type, and coined the term "occult infection" in the late 1930s. Another word for an infection with no symptoms is "asymptomatic".

The Infection Cycle

People should understand that infection and disease is not the same thing. Infection occurs when an organism enters the body and starts to grow. However, disease only occurs if the organism starts to multiply and produce symptoms. Our bodies have tremendous capacity to fight off organisms. Diseases result when these protective mechanism fail or are compromised.

Moreover not all infectious agents are likely to cause disease. For example the polio virus infects many people, but in less than 5% of individuals does it actually cause disease. On the other hand, some organisms are not contagious but very virulent. The mad cow virus kills almost everyone who is infected. The most dangerous organisms are those that are both very virulent and contagious . All organisms must enter the body in order to cause disease. The organism must stick or adhere to a specific cell, invade, colonize and inflict some type of damage to the host. This chain of events is the same for all organisms

Entrance

Entrance to the host generally occurs through the normal openings like the oral cavity, nose, eyes, genitalia, anus, or open wounds. While a few organisms can grow at the initial site of entry, many invade and start to grow in different organs where they are hard to detect. Some organisms grow within the host cells whereas others grow freely in blood. Micro organisms can cause tissue damage by releasing a variety of toxins or destructive enzymes. For example, clostridium tetani releases a toxin which can paralyze muscles, or staphylococcus releases toxins which can produce shock and sepsis.

Infectious agent

For an organism to cause disease, there are several factors that must be met before an infection can occur. The organism must be able to grow, multiply, be able to enter the body and have the ability to cause disease. Infectious agents which cause disease in humans include bacteria, viruses, parasites and fungi.

Reservoir

Reservoir is a place where organisms can thrive and multiply. This may be either inside the human body or outside like in an inanimate environment. For example some organisms may thrive in water (mycobacterium tuberculosis), AC units (legionella), furniture (virus) or in a tick (Lyme disease). The reservoir for a disease is the site where the infectious agent survives. Humans are reservoir for the measles virus because this organism does not infect any other mammals. Beside insects, animals also serve as reservoirs for infectious organism. The rabies virus is carried in many small mammals and wild dogs.

Portal of exit

In order for micro organism to survive and repeat the cycle of infection in other humans, it must have a way to exit the reservoir. For example, if the organism was growing in mouldy water in an air conditioning unit it may spread when the unit is switched on. In other cases, the organism may spread from humans to others when an infected individual coughs. Micro-organisms can also be passed from body fluids, faecal material and urine.

Mode of transmission

Infectious organisms may be transmitted either by direct or indirect contact. Direct contact occurs when an individual comes into contact with the reservoir. This may mean touching infected bodily fluids or drinking contaminated water or being bitten by the deer tick. Direct contact infections can also result from inhalation of infectious organisms found in aerosol particles emitted by sneezing or coughing. Another common means of direct contact transmission involves sexual activity – oral, vaginal or anal sex.

Indirect contact occurs when the organism is able to withstand the harsh environment outside the host for long periods of time and still remain infective when the right opportunity arises. Inanimate objects that are frequently contaminated include toys, furniture, door knobs, tissue wipes or personal care products from an infected individual. Consuming food products and fluid which have been contaminated by contact with an infecting organism is another case of disease transmission by indirect contact.

A common method of transmission in under developed countries is faecal oral transmission. In such cases, sewage water is used to wash food or is consumed. This results in food poisoning. Common disorders which are transmitted by the faecal oral route include cholera, giardia, rotavirus, cryptosporidium, ecoli or tape worms.

All the above modes are examples of horizontal transmission because the infecting organism is transmitted from person to person in the same generation. There are also a variety of infections transmitted vertically – that is from mother to child during the birthing process or fetal development. Common disorders transmitted this way include AIDs, hepatitis, herpes, and cytomegalovirus.

Portal of entry

Organisms need a point of entry. Some enter via the mucus membrane like the mouth, vagina or nose. Others enter via breaks in the skin, for example a surgical incision or a laceration. Sometimes physicians insert tubes or catheters into the bladder which can cause urinary tract infections. Even an intravenous line can become infected at the site where the needle hole was made on the skin.

Susceptibility of host

Most humans are not easily infected. Organisms usually cause infections in people who are weak, sick, malnourished, have cancer, are diabetic or are immuno-suppressed. Individuals who have a suppressed immune system are quickly over powered by the organisms. The majority of chronic or persistent infections occur in individuals who have poor defense mechanism(s).

Persistent viral infections

The most common persistent infections in North America include HIV, hepatitis and herpes simplex. Hepatitis B and C are usually acquired from use of dirty needles, blood transfusions or sexual intercourse. HIV has similar modes of transmission. Once hepatitis has been acquired, it becomes a chronic disorder. While some individuals with hepatitis B may remain asymptomatic, many will show active symptoms and remain infectious. In the long term, both hepatitis B and C can cause liver failure or induce liver cancer. In some cases, the signs and symptoms of liver damage may not appear for 20 years after the infection was initially acquired. Other persistent infections include recurrent ear infection in children, tuberculosis, Lyme disease, Chlamydia and malaria. The problem with recurrent infections is that the organism continues to damage body which eventually results in symptoms. As the body weakens, the individual develops weight loss and extreme fatigue.

Treatment

Appreciation of the infectious cycle is vital in order to recognize available targets for treatment strategies The infection cycle may be broken up and disease may be prevented from developing at different spots along the cycle. For example, direct people to people transmission can be diminished by adequate hygiene, maintaining a sanitary environment as well as health education. Other means of preventing an infection by an organism may be from vaccination.

Bacterial infections are usually treated with antibiotics. There are many types of antibiotics. Depending on the severity and the type of infection, the antibiotic may be given by mouth, injection or may be applied topically. Severe infections of the brain are usually treated with intravenous antibiotics.

Sometimes, multiple antibiotics are used to decrease the risk of resistance and increase efficacy. Antibiotics only work for bacteria and do not affect viruses. Antibiotics work by slowing down the multiplication of bacteria or killing the bacteria. The most common classes of antibiotics used in medicine include penicillin, cephalosporins, aminoglycosides, macrolides, quinolones and tetracyclines.

Prevention

Knowing the chain of infection is important for prevention. For examples techniques like hand washing, gowning and wearing face masks can help prevent infections from the surgeon to the patient or vice versa. Frequent hand washing remains the most important factors in preventing spread of non wanted organisms. Nutrition has to be improved and one has to make changes in life style- like avoiding use of illicit drugs, using a condom and entering an exercise program.

Cooking foods well and avoiding eating foods which have been left outside for a long time is also important. Do not take antibiotics for longer than needed. Long term use of antibiotics leads to resistance and chances of developing opportunistic infections like clostridium difficile colitis.
 

Inflammation of a lymph node is called lymphadenitis. In practice, the distinction between lymphadenopathy and lymphadenitis is rarely made. (Inflammation of lymph channels is called lymphangitis.)

Types

• Localized lymphadenopathy : due to localized spot of infection e.g. an infected spot on the scalp will cause lymph nodes in the neck on that same side to swell up
• Generalized lymphadenopathy : due to generalized infection all over the body e.g. influenza
• persistent generalized lymphadenopathy (PGL) : persisting for a long time, possibly without an apparent cause

Associated conditions

Enlarged lymph nodes are a common symptom in a number of infectious and malignant diseases. It is a recognized symptom of many diseases, which include:

Reactive: acute infection (e.g. bacterial, or viral), or chronic infections (tuberculous lymphadenitis, cat-scratch disease).

• The most distinctive symptom of bubonic plague is extreme swelling of one or more lymph nodes that bulge out of the skin as "buboes." The buboes often become necrotic and may even rupture.
• Infectious mononucleosis is an acute viral infection, the hallmark of which is marked enlargement of the cervical lymph nodes.
• It is also a symptom of cutaneous anthrax, measles and Human African trypanosomiasis, the latter two giving lymphadenopathy in lymph nodes in the neck.
• Toxoplasmosis, a parasitic disease, gives a generalized lymphadenopathy.

Tumoral:

• Primary: Hodgkin lymphoma, non-Hodgkin lymphoma, hairy cell leukemia, give lymphadenopathy in all or a few lymph nodes.
• Secondary: metastasis, Virchow's Node, Neuroblastoma.

Autoimmune etiology: sarcoidosis, systemic lupus erythematosus, rheumatoid arthritis all giving a generalized lymphadenopathy.

Immunocompromised etiology: AIDS. Generalized lymphadenopathy is an early sign of infection with human immunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS). "Lymphadenopathy syndrome" has been used to describe the first symptomatic stage of HIV progression, preceding a diagnosis of AIDS.

Bites from certain venomous snakes, most notably the black mamba, kraits, Australian brown snakes, coral snakes, tiger snakes, taipans, death adders, and some of the more toxic species of cobra.

Patterns of Benign (Reactive) Lymphadenopathy

There are three distinct patterns of benign lymphadenopathy:

• Follicular hyperplasia – Seen in infections, autoimmune disorders, and nonspecific reactions.
• Paracortical hyperplasia – Seen in viral infections, skin diseases, and nonspecific reactions.
• Sinus histiocytosis – Seen in lymph nodes draining limbs, inflammatory lesions, and malignancies.

Bilateral Hilar Lymphadenopathy (BHL)

Bilateral hilar lymphadenopathy is a radiographic term that describes the enlargement of mediastinal lymph nodes. It is easily and most commonly identified by a chest x-ray.

Causes of BHL

The following are causes of BHL:

Sarcoidosis
 

Infection

• Tuberculosis
• Mycoplasma

Malignancy

• Lymphoma
• Carcinoma
• Mediastinal tumors

Organic dust disease

• Silicosis
• Berylliosis

Extrinsic allergic alveolitis

• Such as pigeon fancier's lung

Less common causes also exist:

• Churg-Strauss syndrome
• Human immunodeficiency virus
• Extrinsic allergic alveolitis
• Pneumoconiosis
• Adult-onset Still's disease

The term may refer to:

• EBV infectious mononucleosis, known colloquially as the "kissing disease," caused by Epstein-Barr virus
• CMV infectious mononucleosis, caused by cytomegalovirus

This article is about mononucleosis caused by Epstein-Barr virus.

Classification and external resources

Infectious Mononucleosis (IM) (also known as EBV Infectious Mononucleosis or Pfeiffer's Disease or Filatov's Disease and colloquially as kissing disease—from its oral transmission—or as mono in North America and as glandular fever in other English-speaking countries) is an infectious, very widespread viral disease caused by the Epstein-Barr virus (EBV), one type of herpes virus, to which more than 90% of adults have been exposed. Most people are exposed to the virus as children, when the disease produces no noticeable symptoms or only flu-like symptoms. In underdeveloped countries, people are exposed to the virus in early childhood more often than in developed countries, which is why the disease in its observable form is more common in developed countries. It is most common among adolescents and young adults.

Especially in adolescents and young adults, the disease is characterized by fever, sore throat and fatigue, along with several other possible signs and symptoms. It is primarily diagnosed by observation of symptoms, but suspicion can be confirmed by several diagnostic tests.

The syndrome was described as an infectious process by Nil Filatov in 1887 and independently by Emil Pfeiffer in 1889.

Signs and symptoms

The classical symptoms of mononucleosis are a sore throat, fever, fatigue, weight loss, malaise, pharyngeal inflammation, petechiae and loss of appetite. Common signs include lymphadenopathy (enlarged lymph nodes), splenomegaly (enlarged spleen), hepatitis (refers to inflammation of hepatocytes – cells in the liver) and hemolysis (the bursting of red blood cells). Older adults are less likely to have a sore throat or lymphadenopathy, but are instead more likely to present with hepatomegaly (enlargement of the liver) and jaundice. Rarer signs and symptoms include thrombocytopenia (lower levels of platelets), with or without pancytopenia (lower levels of all types of blood cells), splenic rupture, splenic hemorrhage, upper airway obstruction, pericarditis and pneumonitis. Another rare manifestation of mononucleosis is erythema multiforme.

Mononucleosis is sometimes accompanied by secondary cold agglutinin disease—an autoimmune disease in which abnormal circulating antibodies directed against red blood cells can lead to a form of autoimmune hemolytic anemia. The cold agglutinin detected is of anti-i specificity. Patients with infectious mononucleosis are sometimes misdiagnosed with a streptococcal pharyngitis (because of the classical clinical triad of fever, pharyngitis and adenopathy) and are given antibiotics such as ampicillin or amoxicillin as treatment. Some studies indicate that approximately 80-90% of patients with acute Epstein Barr virus infection treated with such antibiotics develop a red, diffuse rash.

Pathophysiology

Infectious mononucleosis occurs with infection by the Epstein-Barr virus. A similar condition can be caused by cytomegalovirus. Because of this, some sources say that infectious mononucleosis is "usually caused by the Epstein-Barr virus".

The infection is spread via saliva and has an incubation period of 4–7 weeks.

Doctors and researchers are not exactly sure how long someone with the virus stays contagious after symptoms are gone. But it's generally believed that a person can spread the infection for many months after the symptoms are completely gone — some studies show as long as 18 months.

The virus replicates first within epithelial cells in the pharynx (which causes pharyngitis, or sore throat), and later primarily within B cells (which are invaded via their CD21). The host immune response involves cytotoxic (CD8-positive) T cells against infected B lymphocytes, resulting in enlarged atypical lymphocytes (Downey cells).

When the infection is acute (recent onset, instead of chronic), heterophile antibodies are produced.

Diagnosis

The most commonly used diagnostic criterion is the presence of 50% lymphocytes with at least 10% atypical lymphocytes (large, irregular nuclei), while the person also has fever, pharyngitis and adenopathy. Furthermore, it should be confirmed by a serological test. The atypical lymphocytes resembled monocytes when they were first discovered, thus the moniker "mononucleosis" was coined. Diagnostic tests are used to confirm infectious mononucleosis but the disease should be suspected from symptoms prior to the results from hematology. These criteria are specific; however, they are not particularly sensitive and are more useful for research than for clinical use. Only half the patients presenting with the symptoms held by mononucleosis and a positive heterophile antibody test (monospot test) meet the entire criteria. One key procedure is to differentiate between infectious mononucleosis and mononucleosis-like symptoms.

There have been few studies on infectious mononucleosis in a primary care environment, the best of which studied 700 patients, of which 15 were found to have mononucleosis upon a heterophile antibody test. More useful in a diagnostic sense are the signs and symptoms themselves. The presence of splenomegaly, posterior cervical adenopathy, axillary adenopathy, and inguinal adenopathy are the most useful to suspect a diagnosis of infectious mononucleosis. On the other hand, the absence of cervical adenopathy and fatigue are the most useful to dismiss the idea of infectious mononucleosis as the correct diagnosis. The insensitivity of the physical examination in detecting splenomegaly means that it should not be used as evidence against infectious mononucleosis.

In the past the most common test for diagnosing infectious mononucleosis was the heterophile antibody test which involves testing heterophile antibodies by agglutination of guinea pig, sheep and horse red blood cells. As with the aforementioned criteria, this test is specific but not particularly sensitive (with a false-negative rate of as high as 25% in the first week, 5-10% in the second and 5% in the third). 90% of patients have heterophile antibodies by week 3, disappearing in under a year. The antibodies involved in the test do not interact with the Epstein-Barr virus or any of its antigens. More recently, tests that are more sensitive have been developed such as the Immunoglobulin G (IgG) and Immunoglobulin M (IgM) tests. IgG, when positive, reflects a past infection, whereas IgM reflects a current infection. When negative, these tests are more accurate in ruling out infectious mononucleosis. However, when positive, they feature similar sensitivities to the heterophile antibody test. Therefore, these tests are useful for diagnosing infectious mononucleosis in people with highly suggestive symptoms and a negative heterophile antibody test. Another test searches for the Epstein-Barr nuclear antigen, while it is not normally recognizable until several weeks into the disease, and is useful for distinguishing between a recent-onset of infectious mononucleosis and symptoms caused by a previous infection. Elevated hepatic transaminase levels is highly suggestive of infectious mononucleosis, occurring in up to 50% of patients.

Differential diagnosis

Diagnosis of acute infectious mononucleosis should also take into consideration acute cytomegalovirus infection and Toxoplasma gondii infections. These diseases are clinically very similar by their signs and symptoms. Because their management is much the same it is not always helpful, or possible, to distinguish between EBV mononucleosis and cytomegalovirus infection. However, in pregnant women, differentiation of mononucleosis from toxoplasmosis is associated with significant consequences for the fetus.

Acute HIV infection can mimic signs similar to those of infectious mononucleosis and tests should be performed for pregnant women for the same reason as toxoplasmosis.

Other conditions from which to distinguish infectious mononucleosis include leukemia, diphtheria, common cold and influenza (the flu).

Treatment

Self care

Infectious mononucleosis is generally self-limiting and only symptomatic and/or supportive treatments are used. Rest is recommended during the acute phase of the infection, but activity should be resumed once acute symptoms have resolved. Nevertheless heavy physical activity and contact sports should be avoided to mitigate the risk of splenic rupture, for at least one month following initial infection or splenomegaly has resolved, as determined by a treating physician.

Medications

In terms of pharmacotherapies, acetaminophen/paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs) may be used to reduce fever and pain. Prednisone, a corticosteroid, is commonly used as an anti-inflammatory to reduce symptoms of pharyngeal pain, odynophagia, or enlarged tonsils, although its use remains controversial due to the rather limited benefit and the potential of side effects. Intravenous corticosteroids, usually hydrocortisone or dexamethasone, are not recommended for routine use but may be useful if there is a risk of airway obstruction, severe thrombocytopenia, or hemolytic anemia. There is little evidence to support the use of aciclovir, although it may reduce initial viral shedding. However, the antiviral drug valacyclovir has recently been shown to lower or eliminate the presence of the Epstein-Barr virus in subjects afflicted with acute mononucleosis, leading to a significant decrease in the severity of symptoms. Antibiotics are not used as they are ineffective against viral infections. The antibiotics ampicillin and later the related amoxicillin are relatively contraindicated in the case of any coinciding bacterial infections during mononucleosis because their use precipitates a non-allergic rash close to 99% of the time. In a small percentage of cases, mononucleosis infection is complicated by co-infection with streptococcal infection in the throat and tonsils (strep throat). Penicillin or other antibiotics (with the exception of the two mentioned above) should be administered to treat the strep throat. Opioid analgesics are also relatively contraindicated due to risk of respiratory depression.

Prognosis

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

• CNS: Meningitis, encephalitis, hemiplegia, Guillain-Barré syndrome, and transverse myelitis. EBV infection has also been proposed as a risk factor for the development of multiple sclerosis (MS), but this has not been confirmed.
• Hematologic: Hemolytic anemia (direct Coombs test is positive) and various cytopenias; Bleeding (caused by thrombocytopenia).
• Mild jaundice
• Hepatitis (rare)
• Upper airway obstruction (tonsillar hypertrophy) (rare)
• Fulminant disease course (immunocompromised patients) (rare)
• Splenic rupture (rare)
• Myocarditis and pericarditis (rare)

Once the acute symptoms of an initial infection disappear, they will not return. An asymptomatic carrier state exists with a reservoir of infected immune cells. Studies indicate that there is reactivation of the virus which may be accompanied by physical complaints or may be subclinical, and during this phase it can be spread to others. There is the possibility that chronically infected immune cells can, on occasion, develop into Burkitt's lymphoma or Hodgkin's lymphoma
 

Inflammation of a lymph node is called lymphadenitis. In practice, the distinction between lymphadenopathy and lymphadenitis is rarely made. (Inflammation of lymph channels is called lymphangitis.

Types

• Localized lymphadenopathy : due to localized spot of infection e.g. an infected spot on the scalp will cause lymph nodes in the neck on that same side to swell up
• Generalized lymphadenopathy : due to generalized infection all over the body e.g. influenza
• persistent generalized lymphadenopathy (PGL) : persisting for a long time, possibly without an apparent cause

Associated conditions

Enlarged lymph nodes are a common symptom in a number of infectious and malignant diseases. It is a recognized symptom of many diseases, which include:

Reactive: acute infection (e.g. bacterial, or viral), or chronic infections (tuberculous lymphadenitis, cat-scratch disease).

• The most distinctive symptom of bubonic plague is extreme swelling of one or more lymph nodes that bulge out of the skin as "buboes." The buboes often become necrotic and may even rupture.
• Infectious mononucleosis is an acute viral infection, the hallmark of which is marked enlargement of the cervical lymph nodes.
• It is also a symptom of cutaneous anthrax, measles and Human African trypanosomiasis, the latter two giving lymphadenopathy in lymph nodes in the neck.
• Toxoplasmosis, a parasitic disease, gives a generalized lymphadenopathy.

Tumoral:

• Primary: Hodgkin lymphoma, non-Hodgkin lymphoma, hairy cell leukemia, give lymphadenopathy in all or a few lymph nodes.
• Secondary: metastasis, Virchow's Node, Neuroblastoma.

Autoimmune etiology: sarcoidosis, systemic lupus erythematosus, rheumatoid arthritis all giving a generalized lymphadenopathy.

Immunocompromised etiology: AIDS. Generalized lymphadenopathy is an early sign of infection with human immunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS). "Lymphadenopathy syndrome" has been used to describe the first symptomatic stage of HIV progression, preceding a diagnosis of AIDS.

Bites from certain venomous snakes, most notably the black mamba, kraits, Australian brown snakes, coral snakes, tiger snakes, taipans, death adders, and some of the more toxic species of cobra.

Patterns of Benign (Reactive) Lymphadenopathy

There are three distinct patterns of benign lymphadenopathy:

• Follicular hyperplasia – Seen in infections, autoimmune disorders, and nonspecific reactions.
• Paracortical hyperplasia – Seen in viral infections, skin diseases, and nonspecific reactions.
• Sinus histiocytosis – Seen in lymph nodes draining limbs, inflammatory lesions, and malignancies.

Bilateral Hilar Lymphadenopathy (BHL)

Bilateral hilar lymphadenopathy is a radiographic term that describes the enlargement of mediastinal lymph nodes. It is easily and most commonly identified by a chest x-ray.

Causes of BHL

The following are causes of BHL:

Sarcoidosis

Infection

• Tuberculosis
• Mycoplasma

Malignancy

• Lymphoma
• Carcinoma
• Mediastinal tumors

Organic dust disease

• Silicosis
• Berylliosis

Extrinsic allergic alveolitis

• Such as pigeon fancier's lung

Less common causes also exist:

• Churg-Strauss syndrome
• Human immunodeficiency virus
• Extrinsic allergic alveolitis
• Pneumoconiosis
• Adult-onset Still's disease

Many individuals develop a variety of infections but quickly overcome them. However, some individuals are unfortunate and develop chronic or persistent infections. In the majority of cases, persistent infections are caused by viruses and not bacteria. The common viruses that can cause chronic infection include measles, hepatitis, various viruses that affect the brain (mad cow) , herpes, infectious mononucleosis and Cytomegalovirus (CMV). Bacteria can also cause chronic infections in individuals with diabetes, those with compromised immunity and in individuals who smoke.

Diagnosis

The diagnosis of persistent infections can be difficult as there are no specific signs and symptoms. If an infection is suspected, blood, urine and sputum cultures are usually the first step. Chest x ray and stool analysis may provide a clue. Sometimes fluid from the spinal cord is obtained to ensure that there is no brain infection.

Symptoms

• Extreme fatigue which may be ongoing for more than 2-3 months
• Continued weight loss
• Low grade or spiking fever
• Night sweats and chills
• Vague body aches and pain

Primary and secondary

Primary and secondary infection may either refer to succeeding infections or different stages of one and the same infection such as in acute herpes labialis infection. In the latter case, acute infection may also be used, as in acute HIV infection.

Bacterial or viral

Bacterial and viral infections can both cause symptoms such as malaise, fever, and chills. It can be difficult to distinguish which is the cause of a specific infection. It's important to distinguish, because viral infections cannot be cured by antibiotics.

For infection to occur in a human, the chain of events must happen. Infections do not occur by chance but involve many factors. The chain of events involves several steps which include the infectious agent, reservoir, susceptible host, portal of entry, mode of transmission and portal of exit. Each of the links must be present in a chronological order for an infection to develop. Understanding these steps helps health care workers target the infection and prevent it from occurring in the first place. Each one of these links has an integral role in infection

Specific bacterial infections

H pylori is associated with inflammation of the stomach and is a common cause of stomach ulcers and gastritis. At least 10 percent of individuals infected with h pylori develop an ulcer. Moreover, there is an increased risk of stomach cancer after an infection with this organism.

Methicillin-resistant staphylococcus aureus predominantly affects the skin and is considered to be a super bug as it is very resistant to antibiotics. This bacteria is known to generate a variety of toxic enzymes which can lead to vomiting, diarrhea, shock and sepsis. MRSA is quite common in hospitals and today there is a great cause for concern about its spread.

Occult infection

An occult infection is medical terminology for a "hidden" infection, that is, one which presents no symptoms. Dr. Fran Giampietro discovered this type, and coined the term "occult infection" in the late 1930s. Another word for an infection with no symptoms is "asymptomatic".

The Infection Cycle

People should understand that infection and disease is not the same thing. Infection occurs when an organism enters the body and starts to grow. However, disease only occurs if the organism starts to multiply and produce symptoms. Our bodies have tremendous capacity to fight off organisms. Diseases result when these protective mechanism fail or are compromised.

Moreover not all infectious agents are likely to cause disease. For example the polio virus infects many people, but in less than 5% of individuals does it actually cause disease. On the other hand, some organisms are not contagious but very virulent. The mad cow virus kills almost everyone who is infected. The most dangerous organisms are those that are both very virulent and contagious . All organisms must enter the body in order to cause disease. The organism must stick or adhere to a specific cell, invade, colonize and inflict some type of damage to the host. This chain of events is the same for all organisms

Entrance

Entrance to the host generally occurs through the normal openings like the oral cavity, nose, eyes, genitalia, anus, or open wounds. While a few organisms can grow at the initial site of entry, many invade and start to grow in different organs where they are hard to detect. Some organisms grow within the host cells whereas others grow freely in blood. Micro organisms can cause tissue damage by releasing a variety of toxins or destructive enzymes. For example, clostridium tetani releases a toxin which can paralyze muscles, or staphylococcus releases toxins which can produce shock and sepsis.

Infectious agent

For an organism to cause disease, there are several factors that must be met before an infection can occur. The organism must be able to grow, multiply, be able to enter the body and have the ability to cause disease. Infectious agents which cause disease in humans include bacteria, viruses, parasites and fungi.

Reservoir

Reservoir is a place where organisms can thrive and multiply. This may be either inside the human body or outside like in an inanimate environment. For example some organisms may thrive in water (mycobacterium tuberculosis), AC units (legionella), furniture (virus) or in a tick (Lyme disease). The reservoir for a disease is the site where the infectious agent survives. Humans are reservoir for the measles virus because this organism does not infect any other mammals. Beside insects, animals also serve as reservoirs for infectious organism. The rabies virus is carried in many small mammals and wild dogs.

Portal of exit

In order for micro organism to survive and repeat the cycle of infection in other humans, it must have a way to exit the reservoir. For example, if the organism was growing in mouldy water in an air conditioning unit it may spread when the unit is switched on. In other cases, the organism may spread from humans to others when an infected individual coughs. Micro-organisms can also be passed from body fluids, faecal material and urine.

Mode of transmission

Infectious organisms may be transmitted either by direct or indirect contact. Direct contact occurs when an individual comes into contact with the reservoir. This may mean touching infected bodily fluids or drinking contaminated water or being bitten by the deer tick. Direct contact infections can also result from inhalation of infectious organisms found in aerosol particles emitted by sneezing or coughing. Another common means of direct contact transmission involves sexual activity – oral, vaginal or anal sex.

Indirect contact occurs when the organism is able to withstand the harsh environment outside the host for long periods of time and still remain infective when the right opportunity arises. Inanimate objects that are frequently contaminated include toys, furniture, door knobs, tissue wipes or personal care products from an infected individual. Consuming food products and fluid which have been contaminated by contact with an infecting organism is another case of disease transmission by indirect contact.

A common method of transmission in under developed countries is faecal oral transmission. In such cases, sewage water is used to wash food or is consumed. This results in food poisoning. Common disorders which are transmitted by the faecal oral route include cholera, giardia, rotavirus, cryptosporidium, ecoli or tape worms.

All the above modes are examples of horizontal transmission because the infecting organism is transmitted from person to person in the same generation. There are also a variety of infections transmitted vertically – that is from mother to child during the birthing process or fetal development. Common disorders transmitted this way include AIDs, hepatitis, herpes, and cytomegalovirus.

Portal of entry

Organisms need a point of entry. Some enter via the mucus membrane like the mouth, vagina or nose. Others enter via breaks in the skin, for example a surgical incision or a laceration. Sometimes physicians insert tubes or catheters into the bladder which can cause urinary tract infections. Even an intravenous line can become infected at the site where the needle hole was made on the skin.

Susceptibility of host

Most humans are not easily infected. Organisms usually cause infections in people who are weak, sick, malnourished, have cancer, are diabetic or are immuno-suppressed. Individuals who have a suppressed immune system are quickly over powered by the organisms. The majority of chronic or persistent infections occur in individuals who have poor defense mechanism(s).

Persistent viral infections

The most common persistent infections in North America include HIV, hepatitis and herpes simplex. Hepatitis B and C are usually acquired from use of dirty needles, blood transfusions or sexual intercourse. HIV has similar modes of transmission. Once hepatitis has been acquired, it becomes a chronic disorder. While some individuals with hepatitis B may remain asymptomatic, many will show active symptoms and remain infectious. In the long term, both hepatitis B and C can cause liver failure or induce liver cancer. In some cases, the signs and symptoms of liver damage may not appear for 20 years after the infection was initially acquired. Other persistent infections include recurrent ear infection in children, tuberculosis, Lyme disease, Chlamydia and malaria. The problem with recurrent infections is that the organism continues to damage body which eventually results in symptoms. As the body weakens, the individual develops weight loss and extreme fatigue.

Treatment

Appreciation of the infectious cycle is vital in order to recognize available targets for treatment strategies The infection cycle may be broken up and disease may be prevented from developing at different spots along the cycle. For example, direct people to people transmission can be diminished by adequate hygiene, maintaining a sanitary environment as well as health education. Other means of preventing an infection by an organism may be from vaccination.

Bacterial infections are usually treated with antibiotics. There are many types of antibiotics. Depending on the severity and the type of infection, the antibiotic may be given by mouth, injection or may be applied topically. Severe infections of the brain are usually treated with intravenous antibiotics.

Sometimes, multiple antibiotics are used to decrease the risk of resistance and increase efficacy. Antibiotics only work for bacteria and do not affect viruses. Antibiotics work by slowing down the multiplication of bacteria or killing the bacteria. The most common classes of antibiotics used in medicine include penicillin, cephalosporins, aminoglycosides, macrolides, quinolones and tetracyclines.

Prevention

Knowing the chain of infection is important for prevention. For examples techniques like hand washing, gowning and wearing face masks can help prevent infections from the surgeon to the patient or vice versa. Frequent hand washing remains the most important factors in preventing spread of non wanted organisms. Nutrition has to be improved and one has to make changes in life style- like avoiding use of illicit drugs, using a condom and entering an exercise program.

Cooking foods well and avoiding eating foods which have been left outside for a long time is also important. Do not take antibiotics for longer than needed. Long term use of antibiotics leads to resistance and chances of developing opportunistic infections like clostridium difficile colitis.
 

Most people become infected with EBV sometime during their lives, and therefore gain adaptive immunity, preventing repeated sickness from re-infection through EBV antibodies. In the United States, as many as 95% of adults between 35 and 40 years of age have been infected. Infants become susceptible to EBV as soon as maternal antibody protection disappears. Many children become infected with EBV, and these infections usually cause no symptoms or are indistinguishable from the other mild, brief illnesses of childhood. In the United States and in other developed countries, many persons are not infected with EBV in their childhood years. When infection with EBV occurs during adolescence or young adulthood, it causes infectious mononucleosis 35% to 69% of the time. In immunocompromised individuals, the Epstein-Barr virus can also present as an opportunistic infection known as hairy leukoplakia.