15.1 Characteristics of infectious disease  (Page 2/12)

Unlike signs, symptom s of disease are subjective. Symptoms are felt or experienced by the patient, but they cannot be clinically confirmed or objectively measured. Examples of symptoms include nausea, loss of appetite, and pain. Such symptoms are important to consider when diagnosing disease, but they are subject to memory bias and are difficult to measure precisely. Some clinicians attempt to quantify symptoms by asking patients to assign a numerical value to their symptoms. For example, the Wong-Baker Faces pain-rating scale asks patients to rate their pain on a scale of 0–10. An alternative method of quantifying pain is measuring skin conductance fluctuations. These fluctuations reflect sweating due to skin sympathetic nerve activity resulting from the stressor of pain. F. Savino et al. “Pain Assessment in Children Undergoing Venipuncture: The Wong–Baker Faces Scale Versus Skin Conductance Fluctuations.” PeerJ 1 (2013):e37; https://peerj.com/articles/37/

A specific group of signs and symptoms characteristic of a particular disease is called a syndrome . Many syndromes are named using a nomenclature based on signs and symptoms or the location of the disease. [link] lists some of the prefixes and suffixes commonly used in naming syndromes.

Clinicians must rely on signs and on asking questions about symptoms, medical history, and the patient’s recent activities to identify a particular disease and the potential causative agent. Diagnosis is complicated by the fact that different microorganisms can cause similar signs and symptoms in a patient. For example, an individual presenting with symptoms of diarrhea may have been infected by one of a wide variety of pathogenic microorganisms. Bacterial pathogens associated with diarrheal disease include Vibrio cholerae , Listeria monocytogenes , Campylobacter jejuni , and enteropathogenic Escherichia coli ( EPEC ). Viral pathogens associated with diarrheal disease include norovirus and rotavirus. Parasitic pathogens associated with diarrhea include Giardia lamblia and Cryptosporidium parvum . Likewise, fever is indicative of many types of infection, from the common cold to the deadly Ebola hemorrhagic fever .

Finally, some diseases may be asymptomatic or subclinical , meaning they do not present any noticeable signs or symptoms. For example, most individual infected with herpes simplex virus remain asymptomatic and are unaware that they have been infected.