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Common cold
Common cold: mild viral upper respiratory infection caused by over 200 viruses, chiefly rhinoviruses; adults average 2-3 colds yearly; no cure, antibiotics ineffective, no vaccine.
Common Terminology Criteria for Adverse Events
The Common Terminology Criteria for Adverse Events (CTCAE) is a vocabulary and five-point severity scale from the US National Cancer Institute for grading adverse events in cancer trials.
Common variable immunodeficiency
Common variable immunodeficiency (CVID), or common variable immune deficiency, is a primary immunodeficiency with hypogammaglobulinemia from B-cell dysfunction, causing recurrent infections, autoimmunity, and lymphoma risk, treated with immunoglobulin replacement.
Common variable immunodeficiency phenotype due to CD19/CD81 deficiency
CVID phenotype due to CD19/CD81 deficiency (ORPHA:696881), also called CD19 deficiency or CVID type 6: autosomal recessive childhood-onset antibody deficiency from biallelic CD19 or CD81 mutations disrupting the B cell co-receptor complex.
Common warts
Common warts (verruca vulgaris) are benign HPV-caused skin growths, rough cauliflower-like papules on hands, knees, elbows; treated with salicylic acid or cryotherapy, often resolving spontaneously.
Commotio cordis
Commotio cordis, also called cardiac concussion, is ventricular fibrillation triggered by a blunt chest blow during a 10-20 ms vulnerable window of the heartbeat, mainly in young male athletes; survival rose from 10-15% to over 60% with rapid CPR and AED use.
Commotio retinae
Commotio retinae, or Berlin's edema, is transient gray-white outer retinal opacification after blunt closed-globe or blast trauma, seen in about 30% of hospital-treated eye injuries; photoreceptor outer segments are disrupted, and most cases resolve without treatment.
Communicating hydrocephalus
Communicating hydrocephalus (non-obstructive hydrocephalus, ICD-11 8D64.0): impaired CSF reabsorption without ventricular outflow blockage; causes include subarachnoid hemorrhage and meningitis; chronic form is normal pressure hydrocephalus, treated with shunts.
Communication Devices for People with Disabilities
Communication devices for people with disabilities, known as AAC (augmentative and alternative communication), include picture boards, gestures, and speech-generating devices; about 97 million people worldwide may benefit, with no single best system.
Community health
Community health: a public health field focused on the health of a defined population through community engagement, community health centers (US, since 1965), and community health worker programs, distinct from individual clinical care.
Community Health Centers
Community health centers (CHCs, neighborhood health centers, FQHCs) are US nonprofit clinics founded in 1965 under the War on Poverty, patient-governed, serving low-income Americans regardless of ability to pay.
Community Health Nurses
Community health nurses, also called public health nurses, care for whole populations through health promotion, prevention, and home-based care. Rooted in Lillian Wald's 1893 Henry Street Settlement, the field spans contact tracing, vaccination, and nurse home visiting.
Community Health Services
Community Health Services: diagnostic, therapeutic, and preventive health services delivered to individuals in the community (MeSH D003153), spanning community nursing, home care, mental health, and preventive care, delivered by mixed professional teams outside hospitals.
Community Health Workers
Community health workers (CHWs), also called lay or close-to-community health workers, are non-professional, paid or volunteer community-based health workers with under two years of training; ILO ISCO 3253; central to primary health care since Alma-Ata 1978.
Community Hospitals
Community hospitals: small, locally serving hospitals. US AHA category of 5,121 nonfederal short-term hospitals (84% of all US hospitals); in England, GP- and nurse-led local hospitals under 100 beds providing intermediate and rehabilitation care, descended from 1859 cottage hospitals.
Community Mental Health Centers
Community Mental Health Centers (CMHCs) are US facilities created by the 1963 Community Mental Health Act to deliver local psychiatric services, driving deinstitutionalization and later the CCBHC model.
Community Mental Health Services
Community mental health services provide outpatient, team-based, crisis, peer, and supported-living care outside psychiatric institutions; defined by WHO, shaped by the 1963 US Community Mental Health Act, and supported by Cochrane and ACT trial evidence.
Community Participation
Community participation: involvement of community members in community affairs, central to public health since Alma-Ata 1978; typologies include Arnstein's 1969 ladder and Rifkin's mobilization-collaboration-empowerment continuum.
Community reinforcement and family training
Community reinforcement and family training (CRAFT) is a behavioral program that trains families to encourage a loved one's addiction treatment, succeeding about two-thirds of the time.
COMMUNITY study
COMMUNITY (COVID 19 Immunity) study: longitudinal cohort launched April 2020 at Danderyd Hospital, Stockholm, following 2,149 healthcare workers and 118 hospitalized COVID-19 patients with blood and mucosal sampling every 4 months; NCT06784739; known for hybrid immunity and secretory IgA findings.
Community Support
Community support: help from family, friends, neighbors, and community organizations, a social determinant of health linked to lower mortality and hardship, delivered via community health workers, peer support, and social prescribing.
Community trial
A community trial is an epidemiology study design in which whole communities, rather than individuals, are randomized to a health intervention, capturing population-level and herd effects.
Community-acquired pneumonia
Community-acquired pneumonia (CAP) is lung infection acquired outside hospital, caused mainly by Streptococcus pneumoniae and respiratory viruses. Diagnosed clinically plus chest imaging; managed with timely antibiotics, severity scores (CRB65, severe CAP criteria), and, per 2025 ATS guidance, corticosteroids in severe cases.
Comorbidities of rheumatoid arthritis
The comorbidities of rheumatoid arthritis are additional conditions that drive excess deaths in RA, chiefly cardiovascular disease, serious infection, osteoporosis, and roughly doubled lymphoma risk, with 75.7% of patients having at least one other long-term condition.
Comorbidity
Comorbidity: co-occurrence of more than one disease or condition in one person; coined by Alvan Feinstein in 1970; measured with indices such as Charlson and Elixhauser; related to but distinct from multimorbidity.
Companion diagnostic
A companion diagnostic is an in vitro test essential for the safe, effective use of a specific drug, identifying patients likely to benefit or suffer serious adverse reactions.
Comparative auditory physiology
Comparative auditory physiology studies how vertebrate ears detect and discriminate sound across species, using differences among fish, amphibians, reptiles, birds, and mammals to interpret human hearing.
Comparison of birth control methods
Comparison of birth control methods (contraception): IUDs, implants, pills, patch, ring, injection, condoms, fertility awareness, sterilization, and emergency contraception, compared by typical use failure rates, duration, STI protection, reversibility, and user preferences.
Comparison of MD and DO in the United States
MD vs DO in the US: the two physician degree paths, allopathic MD and osteopathic DO, differ in philosophy, OMT training, and COMLEX vs USMLE exams, but outcome studies show similar patient care, and both match through the single ACGME accreditation system.
Comparison of the healthcare systems in Canada and the United States
Canada vs US healthcare: Canada runs tax-funded provincial single-payer Medicare with universal coverage and no cost sharing; the US uses multi-payer employer and public insurance, spends over 16% of GDP, and ranks last among 10 high-income countries.