Question: What are characteristics of organisms that can cause disease, but live on us everyday without typically giving us disease?
About the article "Bacteria", section "Pathogens".

Candidate passages:
A parasitic disease is an infectious disease caused or transmitted by a parasite.
Many parasites do not cause diseases.
Parasitic diseases can affect practically all living organisms, including plants and mammals.
The study of parasitic diseases is called parasitology.
Some parasites like "Toxoplasma gondii and Plasmodium" spp.
can cause disease directly, but other organisms can cause disease by the toxins that they produce. 
This disease is diagnosed differently according to the stage of the disease.
There are different characteristics or signs of the disease throughout these different stages.
During the beginning of the disease, doctors can diagnose the patient according to the presence of cerebral spinal fluid lymphocytosis.
CT scans or MRIs can be performed in order to find calcifications in the brain, problems with the white matter, and/or cerebral atrophy.
There are other different diagnostic criteria, such as lesions and infections, that can be helpful depending on what stage of the disease the patient is in.
In addition, there are specific genes that have been shown to be mutated.
Thus, analysis of a patient's genome can also help to determine if the patient does in fact have the disease.
If these genes are mutated, they will cause the signs and symptoms of the disease.
Research has not yet proven how or when the signs and symptoms of the disease begin. 
As previously stated, the human mouth contains around 500 to 1000 types of bacteria that have various functions.
While some of the bacteria in our mouths are harmful and can cause serious illness, much of our oral bacteria are actually beneficial in preventing disease.
Streptococci make up a large part of oral bacteria.
There are four main species within streptococci: the mutans, salivarius, anginosus, and mitis groups.
Streptococcus mutans make up a large majority of what affects our mouths.
As a matter of fact, it is “the biggest culprit in tooth decay” as it promotes the production of acids and enzymes.
The acids cause the collapse of enamel opening the door for the formation of decay.
The enzymes “leach down the tooth and begin to dissolve the ligaments and bone that help to hold the teeth in your mouth.” By turning simple sugars and carbohydrates into acids and enzymes that dissolve tooth enamel, this bacteria can leave a person with lasting dental problems.
According to Dr. Robert Gandola, a dentist, “A number of bacteria can cause decay many are suspected in periodontal (gum) disease.”As mentioned, oral bacteria also help fight disease-producing germs that try to come in through the mouth.
These bacteria work with our immune system to keep our bodies disease free.
For example, some of these bacteria produce organic acids that kill the organisms that cause intestinal problems.
Without these good bacteria, our immune systems would be constantly bombarded by airborne and saliva-transferred germs.
Bacteria are also needed to control the growth of fungus.
“Balance between all the different bacteria and fungus are critical” or else the “fungus overgrows and takes over.” So, ironically, though bacteria have the potential to harm us, our mouth and the good bacteria in it are the body’s first line of defense.
These bacteria are transmitted to a human early in their childhood through their contact with their caretakers by kisses or food premastication. 
Sudden arrhythmic death syndrome (SADS), is a term used as part of sudden unexpected death syndrome to describe sudden death due to cardiac arrest brought on by an arrhythmia in the absence of any structural heart disease on autopsy.
The most common cause of sudden death in the US is coronary artery disease.
Approximately 180,000 to 250,000 people die suddenly of this cause every year in the US.
SADS occurs from other causes.
There are many inherited conditions and heart diseases that can affect young people which can subsequently cause sudden death without advance symptoms.
Causes of SADS in young people include viral myocarditis, long QT syndrome, Brugada syndrome, Catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy and arrhythmogenic right ventricular dysplasia. 
In many cases, the terms "disease", "disorder", "morbidity" and "illness" are used interchangeably.
In some situations, specific terms are considered preferable.
Disease The term "disease" broadly refers to any condition that impairs normal function, and is therefore associated with dysfunction of normal homeostasis.
Commonly, the term "disease" is used to refer specifically to infectious diseases, which are clinically evident diseases that result from the presence of pathogenic microbial agents, including viruses, bacteria, fungi, protozoa, multicellular organisms, and aberrant proteins known as prions.
An infection that does not and will not produce clinically evident impairment of normal functioning, such as the presence of the normal bacteria and yeasts in the gut, or of a passenger virus, is not considered a disease.
By contrast, an infection that is asymptomatic during its incubation period, but expected to produce symptoms later, is usually considered a disease.
Non-infectious diseases are all other diseases, including most forms of cancer, heart disease, and genetic disease.
Illness "Illness" and "sickness" are generally used as synonyms for "disease".
However, this term is occasionally used to refer specifically to the patient's personal experience of his or her disease.
In this model, it is possible for a person to have a disease without being ill (to have an objectively definable, but asymptomatic, medical condition), and to be "ill" without being "diseased" (such as when a person perceives a normal experience as a medical condition, or medicalizes a non-disease situation in his or her life).
Illness is often not due to infection, but to a collection of evolved responses—sickness behavior by the body—that helps clear infection.
Such aspects of illness can include lethargy, depression, anorexia, sleepiness, hyperalgesia, and inability to concentrate.
In medicine, a disorder is a functional abnormality or disturbance.
Medical disorders can be categorized into mental disorders, physical disorders, genetic disorders, emotional and behavioral disorders, and functional disorders.
The term "disorder" is often considered more value-neutral and less stigmatizing than the terms "disease" or "illness", and therefore is preferred terminology in some circumstances.
In mental health, the term mental disorder is used as a way of acknowledging the complex interaction of biological, social, and psychological factors in psychiatric conditions.
However, the term "disorder" is also used in many other areas of medicine, primarily to identify physical disorders that are not caused by infectious organisms, such as metabolic disorders.
Medical condition A medical condition is a broad term that includes all diseases and disorders.
While the term "medical condition" generally includes mental illnesses, in some contexts the term is used specifically to denote any illness, injury, or disease except for mental illnesses.
The Diagnostic and Statistical Manual of Mental Disorders (DSM), the widely used psychiatric manual that defines all mental disorders, uses the term "general medical condition" to refer to all diseases, illnesses, and injuries except for mental disorders.
This usage is also commonly seen in the psychiatric literature.
Some health insurance policies also define a "medical condition" as any illness, injury, or disease except for psychiatric illnesses.
As it is more value-neutral than terms like "disease", the term "medical condition" is sometimes preferred by people with health issues that they do not consider deleterious.
On the other hand, by emphasizing the medical nature of the condition, this term is sometimes rejected, such as by proponents of the autism rights movement.
The term "medical condition" is also a synonym for "medical state", in which case it describes an individual patient's current state from a medical standpoint.
This usage appears in statements that describe a patient as being "in critical condition", for example.
Morbidity () is a diseased state, disability, or poor health due to any cause.
The term may be used to refer to the existence of any form of disease, or to the degree that the health condition affects the patient.
Among severely ill patients, the level of morbidity is often measured by ICU scoring systems.
Comorbidity is the simultaneous presence of two or more medical conditions, such as schizophrenia and substance abuse.
In epidemiology and actuarial science, the term "morbidity rate" can refer to either the incidence rate, or the prevalence of a disease or medical condition.
This measure of sickness is contrasted with the mortality rate of a condition, which is the proportion of people dying during a given time interval.
Syndrome A syndrome is the association of several medical signs, symptoms, and or other characteristics that often occur together.
Some syndromes, such as Down syndrome, have only one cause; others, such as Parkinsonian syndrome, have multiple possible causes.
In other cases, the cause of the syndrome is unknown.
A familiar syndrome name often remains in use even after an underlying cause has been found, or when there are a number of different possible primary causes.
Predisease Predisease is a type of disease creep or medicalization in which currently healthy people with risk factors for disease, but no evidence of actual disease, are told that they are sick.
Prediabetes and prehypertension are common examples.
Labeling a healthy person with predisease can result in overtreatment, such as taking drugs that only help people with severe disease, or in useful preventive measures, such as motivating the person to get a healthful amount of physical exercise.